Sign in to follow this  

OpenGL Shadow Mapping problems

This topic is 3787 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi! I'm working on a graphics project, and I wanted to add simple shadows to it. I tried to do shadow mapping like in Shadow Mapping Tutorial, but it didn't exactly work. I'm basically having 2 different problems: 1) This seems to be an ATi only problem. As soon as I enable shadowing (e.g. render to a depth map and use it), performance drops to about 3-4 FPS. Otherwise it's smooth (no FPS counter, but it's at least 30 FPS, since there are no lags). Funny thing is, the same happens when I use that tutorial's example - a trivial scene at 5 FPS. This all happened on my X800 GTO2. Then I tested it on nVidia's 6600GT, and it works just fine - tutorial's example at 100FPS, and mine quite smooth. I tried different texture filtering (nearest/linear/mipmap), different Z-buffer depths (16/24/32), different depth map depths (16/24/32/default), and nothing helped - same 3-4 FPS. Seems like copying to the depth map takes huge amount of time. Here's what I use now:
// Initialize depth texture (my texture loader, basically sets the passed params)
if (!glTex::UseTex(NULL, DepthSize, DepthSize, TexDepth, GL_DEPTH_COMPONENT, GL_LINEAR_MIPMAP_LINEAR, GL_CLAMP_TO_EDGE)) return false;
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE, GL_ALPHA);

// Update depth texture
glBindTexture(GL_TEXTURE_2D, TexDepth);
glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, DepthSize, DepthSize);

I should note that I'm not using pbuffers/FBO - only glCopyTexSubImage2D. I know that's inefficient, but FBOs are only available on new hardware, and pbuffers aren't that easy to work with. But this shouldn't be the problem since I'm also using cube mapping, and that is 6 copies. If cube mapping works fast, why shadow mapping doesn't? (Just in case, I updated the drivers - no change) Did anyone have this problem before? I've only seen similar drop in performance when I used NPOT textures with mipmaps on ATi (again, nVidia didn't seem to care). Could this be remedied by using pbuffers? If anyone has an ATi card, please try to download the demo of the tutorial and tell the FPS you get (it could be due to my computer/driver/card combo). 2) This problem is unrelated, and is actually about the algorithm. In the tutorial, only back faces are rendered to the depth map. I cannot do that since I have non-closed (flat) objects in my scene. So what I do is render whole scene, same way, and use polygon offset. Now when rendering, I tried to render bright first, shadowed second, but eventually used the opposite (with depth test of GL_LESS). This is because I have alpha blending in the scene (the grass), and it produced weird bright spots because bright didn't overwrite dark but combined with it. Here's how I render:
// Snap shadow map
SnapDepth(TexDepth);

// Go to reflective object position and snap cubemap
glLoadTransposeMatrixd((double*)RefObjMat);
SnapCubemap(TexCubemap);

// Draw objects (bright light)
glLoadTransposeMatrixd((double*)CameraViewMat);
glAlphaFunc(GL_GEQUAL, 0.01f);
glEnable(GL_ALPHA_TEST);
DrawObjects();
glDisable(GL_ALPHA_TEST);

// Draw objects (dim light)
glDepthFunc(GL_LESS);
glLoadTransposeMatrixd((double*)CameraViewMat);
DrawObjects(3);
glDepthFunc(GL_LEQUAL);

First shadowed, then bright almost works. The problem can be seen in the following screenshot: Image Hosted by ImageShack.us Image Hosted by ImageShack.us First image is camera view, second is light view. Object is a concave mirror. In camera view, you can see the weird bright strip between 2 shadowed parts. That is between shadow due to lighting model (opposite side to light) and shadow due to shadow mapping (self-shadowing). Reversing bright/dark render order didn't change anything regarding that strip. I guess that the reason for it is either imprecision (512*512 depth map, maybe 2K*2K could fix that, but that's too big), or polygon offset (moving shadow back a bit). I can't remove polygon offset because then whole scene would be Z-fighting. Any ideas how to fix it, leaving the mirror completely flat? (A solution is making it a shape with volume, but that's not what I want) P.S. shadow looks rather ugly, any way to improve that without using shaders? (OpenGL 1.4 only). I know nVidia has some kind of PCF built in and enabled through GL_LINEAR filter, but it doesn't seem to work on ATi. Thanks in advance!

Share this post


Link to post
Share on other sites
Anyone?

Even if you can't help me to solve the problems, I'd appreciate if you downloaded the tutorial demo, and told me what FPS you get on what hardware. At least I'd know if it's an ATi issue or something else. Surely I'm not the only one with an ATi card here :-)

Share this post


Link to post
Share on other sites
The FPS drop on the ATI card could be caused by unsupported extensions. If something isn't supported by the hardware, OpenGL driver can silently switch to software rendering mode. Try using gDEBugger to figure out what's going on. Also, glGetError could be useful.

EDIT:
Try replacing glCopyTexSubImage2D with glCopyTexImage2D.

Share this post


Link to post
Share on other sites
I tried the following:

1) glCopyTexSubImage2D
2) glCopyTexImage2D
3) glReadPixels + glTexImage2D

Performance is roughly the same - 3-4 FPS. Commenting these out effectively disables shadows, but performance goes up to a reasonable level again.

Software rendering seems like a good reason for this behaviour (though what exactly is there to emulate in software - array copying?)

I'll try gDEBugger, never used it, and see what happens.

Though if it works fine on ATi 9600, it does make it more likely that it's my computer making problems than the code. Or maybe some X??? series driver bug...

Share this post


Link to post
Share on other sites
Quote:
Original post by Seroja

Performance is roughly the same - 3-4 FPS. Commenting these out effectively disables shadows, but performance goes up to a reasonable level again.



Sounds like glCopy family of functions is implemented slowly in the X800 driver. Perhaps it's doing something stupid like:

glFinish();
memcpy(...);

One way you can make it run faster on the X800 is by using FBO (Frame Buffer Object). With an FBO there is no need to do glCopy, you can just render to texture directly.

Share this post


Link to post
Share on other sites
Quote:
Original post by deathkrush
Quote:
Original post by Seroja

Performance is roughly the same - 3-4 FPS. Commenting these out effectively disables shadows, but performance goes up to a reasonable level again.



Sounds like glCopy family of functions is implemented slowly in the X800 driver. Perhaps it's doing something stupid like:

glFinish();
memcpy(...);

One way you can make it run faster on the X800 is by using FBO (Frame Buffer Object). With an FBO there is no need to do glCopy, you can just render to texture directly.


I wish I could. It's an academic project, and we have only Intel's embedded chipsets (915G). It has OpenGL 1.4, so that's what I'm targeting. I'll try tomorrow the code on that chipset, but for now I've been working at home, keeping an eye on extensions I use.

FBOs didn't even make into a standard, and I haven't seen them supported on anyt embedded chipset (e.g. only nVidia and ATi seem to support them). They aren't even ARB, only EXT, and didn't make into any OpenGL standard (yet?).

If it won't work on Intels, I'll either fallback to planar shadows or go for pbuffers (both alternatives sound bad, especially since I might waste time on pbuffers only to find that performance didn't improve).

glCopy could indeed be implemented badly, but:
1) It's 1 copy of 512*512 depth texture per frame, why would it decrease preformance x3 or even x4?
2) I use same glCopy for cube mapping, which is 6 256*256 RGB(A) textures, and even increasing that to 6 512*512 textures didn't hurt performance as much.

I used gDEBugger, 200k calls per frame :S Code doesn't seem that long, and I used display lists (I have a skybox, 3 spheres, grass grid of about 6*6, + cubemapping and shadow mapping). OK, spheres are well-tesselated, but still I doubt I need VBOs for such low amount of geometry.
Anyway, I used removal of draw commands feature, brought that down to 5k, FPS went up by 1 -> which means enormous amount of GL calls isn't the problem. And previous version had 90k calls and worked fine.

Seems like either I have something weird on my computer, or I discovered a render path that the driver devs haven't thought of. Actually, I didn't find anywhere any shadow mapping with glCopy, except for that tutorial. Others use cube shadow maps / pbuffers / FBOs / etc. Maybe it's a subtle hint that I'm not using hardware the way it should be used...

Share this post


Link to post
Share on other sites
Quote:
Original post by Seroja

glCopy could indeed be implemented badly, but:
1) It's 1 copy of 512*512 depth texture per frame, why would it decrease preformance x3 or even x4?

If the OpenGL driver is doing something silly like using the CPU to copy data, that would kill performance because accessing VRAM from CPU is very slow on many graphic cards. Think 10MB/s instead of 10GB/s !!!

Quote:
Original post by Seroja
2) I use same glCopy for cube mapping, which is 6 256*256 RGB(A) textures, and even increasing that to 6 512*512 textures didn't hurt performance as much.

Maybe the OpenGL driver supports copying an RGBA texture using the GPU, but it falls back to 10MB/s for depth textures? In that case you can lie to the driver and say it's an RGBA texture so it does a fast copy and then change it back to DEPTH texture. You can use PBO (pixel buffer object) for that.

Share this post


Link to post
Share on other sites
Quote:
Original post by deathkrush
Quote:
Original post by Seroja

glCopy could indeed be implemented badly, but:
1) It's 1 copy of 512*512 depth texture per frame, why would it decrease preformance x3 or even x4?

If the OpenGL driver is doing something silly like using the CPU to copy data, that would kill performance because accessing VRAM from CPU is very slow on many graphic cards. Think 10MB/s instead of 10GB/s !!!

Quote:
Original post by Seroja
2) I use same glCopy for cube mapping, which is 6 256*256 RGB(A) textures, and even increasing that to 6 512*512 textures didn't hurt performance as much.

Maybe the OpenGL driver supports copying an RGBA texture using the GPU, but it falls back to 10MB/s for depth textures? In that case you can lie to the driver and say it's an RGBA texture so it does a fast copy and then change it back to DEPTH texture. You can use PBO (pixel buffer object) for that.



OK, now that makes sense. But I don't think I can fool the driver that easily. FBOs are out of my reach, so PBOs definitely are (not that I know how to use them anyway). Or is it possible with something more simple like pbuffers?

Otherwise, I don't know how to do it. If I tell it's RGBA, it will copy black (since I disable color writes during depth map creation pass). If I glRead the depth, I'll get same performance drop.

Maybe there is a way to convert depth (Z-buffer value) to color... Actually why not... It would be quite cumbersome with the way my code is set up, but the depth pass could have color writes enabled, everything disabled, except for eye-linear texture giving value according to distance from eye (which is the Z value). Will glCopy be able to copy RGBA into depth texture? e.g. what would the following call result with:
glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 0, 0, DepthSize, DepthSize, 0);
If a depth texture is bound?

OK, I actually tried that while writing the post :-)
I didn't do the eye-linear thing, but I bound the scene rendered from light view as a texture. Shadow became colorized :D
Actually, I think it ended up with some interesting projective texture. Unfortunately the R-coordinate comparison won't work this way (RGBA doesn't have R-coordinate). Speed did get up to the reasonable level, but this isn't shadow mapping (at least not without a shader). Unless I can convince OpenGL to use s or t as if they were the r coordinate - which I have no idea of how to do.

I still have doubts about this being a driver bug. Somehow, almost everything that didn't work for me in OpenGL ended up being my own bug.

Share this post


Link to post
Share on other sites
Quote:
Original post by Seroja

OK, now that makes sense. But I don't think I can fool the driver that easily. FBOs are out of my reach, so PBOs definitely are (not that I know how to use them anyway). Or is it possible with something more simple like pbuffers?



Is ARB_render_texture supported? If so, it can be used in combination with pbuffers to achieve the same thing as FBO.

Share this post


Link to post
Share on other sites
Render texture isn't supported, so I can only use glCopy.

Tested it today on Intel and it works fine :D
So it's either my computer's or ATi's bad.

Positive: Intel (which turned out to be 945G not 915G), in addition to properly shadowing, seems to also support PCF. I used GL_LINEAR_MIPMAP_LINEAR, turned on blending, changed order of drawing to first dim then bright, and it indeed became quite smooth. Without blending, there were "halos" around shadows (that's where alpha isn't 1 or 0). If Intel can do it and nVidia can do it, why ATi can't?

Negative: The grass started getting "animated" - e.g. I see the triangles that make up the grass, and texture is moving on them. I distorted the texture coordinates and didn't supply proper Q coordinate, I know, but on nVidia and ATi at least the behavior is stable (so when moving the grass plane texture sticks to it and doesn't move). Oh, and Intel's driver doesn't know that fog enable is part of the enable bits, so I had to change PushAttrib to all bits to make it work.


Thanks for the help, I'm pretty much OK with the situation now. I still would like to see someone with an X800 (or similar) tell me if they have same low FPS.


Edit: just a quick question that came into my mind - assuming GPU has PCF, if a fragment has alpha of 0.3, and PCF says 50% coverage (0.5 alpha), what will be the final alpha of te fragment? 0.15, 0.5 or anything else?

[Edited by - Seroja on August 6, 2007 1:50:31 PM]

Share this post


Link to post
Share on other sites
Quote:
Original post by Seroja
Render texture isn't supported, so I can only use glCopy.

Tested it today on Intel and it works fine :D
So it's either my computer's or ATi's bad.

Positive: Intel (which turned out to be 945G not 915G), in addition to properly shadowing, seems to also support PCF. I used GL_LINEAR_MIPMAP_LINEAR, turned on blending, changed order of drawing to first dim then bright, and it indeed became quite smooth. Without blending, there were "halos" around shadows (that's where alpha isn't 1 or 0). If Intel can do it and nVidia can do it, why ATi can't?

Negative: The grass started getting "animated" - e.g. I see the triangles that make up the grass, and texture is moving on them. I distorted the texture coordinates and didn't supply proper Q coordinate, I know, but on nVidia and ATi at least the behavior is stable (so when moving the grass plane texture sticks to it and doesn't move). Oh, and Intel's driver doesn't know that fog enable is part of the enable bits, so I had to change PushAttrib to all bits to make it work.


Thanks for the help, I'm pretty much OK with the situation now. I still would like to see someone with an X800 (or similar) tell me if they have same low FPS.


Edit: just a quick question that came into my mind - assuming GPU has PCF, if a fragment has alpha of 0.3, and PCF says 50% coverage (0.5 alpha), what will be the final alpha of te fragment? 0.15, 0.5 or anything else?


I can't contribute anything other than the fact that my X850XT runs that demo at a constant 4FPS [sad].

Share this post


Link to post
Share on other sites
Quote:
Original post by agi_shi
Quote:
Original post by Seroja
Render texture isn't supported, so I can only use glCopy.

Tested it today on Intel and it works fine :D
So it's either my computer's or ATi's bad.

Positive: Intel (which turned out to be 945G not 915G), in addition to properly shadowing, seems to also support PCF. I used GL_LINEAR_MIPMAP_LINEAR, turned on blending, changed order of drawing to first dim then bright, and it indeed became quite smooth. Without blending, there were "halos" around shadows (that's where alpha isn't 1 or 0). If Intel can do it and nVidia can do it, why ATi can't?

Negative: The grass started getting "animated" - e.g. I see the triangles that make up the grass, and texture is moving on them. I distorted the texture coordinates and didn't supply proper Q coordinate, I know, but on nVidia and ATi at least the behavior is stable (so when moving the grass plane texture sticks to it and doesn't move). Oh, and Intel's driver doesn't know that fog enable is part of the enable bits, so I had to change PushAttrib to all bits to make it work.


Thanks for the help, I'm pretty much OK with the situation now. I still would like to see someone with an X800 (or similar) tell me if they have same low FPS.


Edit: just a quick question that came into my mind - assuming GPU has PCF, if a fragment has alpha of 0.3, and PCF says 50% coverage (0.5 alpha), what will be the final alpha of te fragment? 0.15, 0.5 or anything else?


I can't contribute anything other than the fact that my X850XT runs that demo at a constant 4FPS [sad].



Thanks. That means that it's most probable that this is an X??? / X8?? series bug. Any point notifying ATi about it? I mean, glCopy is old and isn't widely used (especially on a card with FBOs), and X800 isn't a new card they really care about. If yes, anyone knows how / where?

Share this post


Link to post
Share on other sites
Quote:
Original post by Seroja
Quote:
Original post by agi_shi
Quote:
Original post by Seroja
Render texture isn't supported, so I can only use glCopy.

Tested it today on Intel and it works fine :D
So it's either my computer's or ATi's bad.

Positive: Intel (which turned out to be 945G not 915G), in addition to properly shadowing, seems to also support PCF. I used GL_LINEAR_MIPMAP_LINEAR, turned on blending, changed order of drawing to first dim then bright, and it indeed became quite smooth. Without blending, there were "halos" around shadows (that's where alpha isn't 1 or 0). If Intel can do it and nVidia can do it, why ATi can't?

Negative: The grass started getting "animated" - e.g. I see the triangles that make up the grass, and texture is moving on them. I distorted the texture coordinates and didn't supply proper Q coordinate, I know, but on nVidia and ATi at least the behavior is stable (so when moving the grass plane texture sticks to it and doesn't move). Oh, and Intel's driver doesn't know that fog enable is part of the enable bits, so I had to change PushAttrib to all bits to make it work.


Thanks for the help, I'm pretty much OK with the situation now. I still would like to see someone with an X800 (or similar) tell me if they have same low FPS.


Edit: just a quick question that came into my mind - assuming GPU has PCF, if a fragment has alpha of 0.3, and PCF says 50% coverage (0.5 alpha), what will be the final alpha of te fragment? 0.15, 0.5 or anything else?


I can't contribute anything other than the fact that my X850XT runs that demo at a constant 4FPS [sad].



Thanks. That means that it's most probable that this is an X??? / X8?? series bug. Any point notifying ATi about it? I mean, glCopy is old and isn't widely used (especially on a card with FBOs), and X800 isn't a new card they really care about. If yes, anyone knows how / where?


TBH, I don't see any point. They probably know about it already (well, they are the ones who wrote the drivers [lol])... and besides, these cards are behind 2 generations already [wink].

Speaking of drivers... try out the Omega drivers. They're made "for" games. Maybe they fix this issue?

Share this post


Link to post
Share on other sites
Quote:
Original post by agi_shi
Quote:
Original post by Seroja
Quote:
Original post by agi_shi
Quote:
Original post by Seroja
Render texture isn't supported, so I can only use glCopy.

Tested it today on Intel and it works fine :D
So it's either my computer's or ATi's bad.

Positive: Intel (which turned out to be 945G not 915G), in addition to properly shadowing, seems to also support PCF. I used GL_LINEAR_MIPMAP_LINEAR, turned on blending, changed order of drawing to first dim then bright, and it indeed became quite smooth. Without blending, there were "halos" around shadows (that's where alpha isn't 1 or 0). If Intel can do it and nVidia can do it, why ATi can't?

Negative: The grass started getting "animated" - e.g. I see the triangles that make up the grass, and texture is moving on them. I distorted the texture coordinates and didn't supply proper Q coordinate, I know, but on nVidia and ATi at least the behavior is stable (so when moving the grass plane texture sticks to it and doesn't move). Oh, and Intel's driver doesn't know that fog enable is part of the enable bits, so I had to change PushAttrib to all bits to make it work.


Thanks for the help, I'm pretty much OK with the situation now. I still would like to see someone with an X800 (or similar) tell me if they have same low FPS.


Edit: just a quick question that came into my mind - assuming GPU has PCF, if a fragment has alpha of 0.3, and PCF says 50% coverage (0.5 alpha), what will be the final alpha of te fragment? 0.15, 0.5 or anything else?


I can't contribute anything other than the fact that my X850XT runs that demo at a constant 4FPS [sad].



Thanks. That means that it's most probable that this is an X??? / X8?? series bug. Any point notifying ATi about it? I mean, glCopy is old and isn't widely used (especially on a card with FBOs), and X800 isn't a new card they really care about. If yes, anyone knows how / where?


TBH, I don't see any point. They probably know about it already (well, they are the ones who wrote the drivers [lol])... and besides, these cards are behind 2 generations already [wink].

Speaking of drivers... try out the Omega drivers. They're made "for" games. Maybe they fix this issue?



I *was* on Omega before I got this bug. Then I decided to update drivers, got Omega's latest, which didn't work for some reason. So currently I'm on latest Catalyst.

Which means this is a "serious" bug - that has been for some time in drivers. But this is likely due to the technique not being used in games and thus considered low priority (or maybe they never even noticed the bug).

Share this post


Link to post
Share on other sites

This topic is 3787 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Forum Statistics

    • Total Topics
      628754
    • Total Posts
      2984518
  • Similar Content

    • By test opty
      Hi,

      Please read the Linking Vertex Attributes section of this page. I've read the term a vertex attribute many times in this page but I'm not sure what it means for real or what the author meant by that.
      If possible please tell me the exact meaning the author meant by vertex attributes.
    • By alex1997
      I'm looking to render multiple objects (rectangles) with different shaders. So far I've managed to render one rectangle made out of 2 triangles and apply shader to it, but when it comes to render another I get stucked. Searched for documentations or stuffs that could help me, but everything shows how to render only 1 object. Any tips or help is highly appreciated, thanks!
      Here's my code for rendering one object with shader!
       
      #define GLEW_STATIC #include <stdio.h> #include <GL/glew.h> #include <GLFW/glfw3.h> #include "window.h" #define GLSL(src) "#version 330 core\n" #src // #define ASSERT(expression, msg) if(expression) {fprintf(stderr, "Error on line %d: %s\n", __LINE__, msg);return -1;} int main() { // Init GLFW if (glfwInit() != GL_TRUE) { std::cerr << "Failed to initialize GLFW\n" << std::endl; exit(EXIT_FAILURE); } // Create a rendering window with OpenGL 3.2 context glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); glfwWindowHint(GLFW_RESIZABLE, GL_FALSE); // assing window pointer GLFWwindow *window = glfwCreateWindow(800, 600, "OpenGL", NULL, NULL); glfwMakeContextCurrent(window); // Init GLEW glewExperimental = GL_TRUE; if (glewInit() != GLEW_OK) { std::cerr << "Failed to initialize GLEW\n" << std::endl; exit(EXIT_FAILURE); } // ----------------------------- RESOURCES ----------------------------- // // create gl data const GLfloat positions[8] = { -0.5f, -0.5f, 0.5f, -0.5f, 0.5f, 0.5f, -0.5f, 0.5f, }; const GLuint elements[6] = { 0, 1, 2, 2, 3, 0 }; // Create Vertex Array Object GLuint vao; glGenVertexArrays(1, &vao); glBindVertexArray(vao); // Create a Vertex Buffer Object and copy the vertex data to it GLuint vbo; glGenBuffers(1, &vbo); glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, sizeof(positions), positions, GL_STATIC_DRAW); // Specify the layout of the vertex data glEnableVertexAttribArray(0); // layout(location = 0) glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0); // Create a Elements Buffer Object and copy the elements data to it GLuint ebo; glGenBuffers(1, &ebo); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW); // Create and compile the vertex shader const GLchar *vertexSource = GLSL( layout(location = 0) in vec2 position; void main() { gl_Position = vec4(position, 0.0, 1.0); } ); GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER); glShaderSource(vertexShader, 1, &vertexSource, NULL); glCompileShader(vertexShader); // Create and compile the fragment shader const char* fragmentSource = GLSL( out vec4 gl_FragColor; uniform vec2 u_resolution; void main() { vec2 pos = gl_FragCoord.xy / u_resolution; gl_FragColor = vec4(1.0); } ); GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER); glShaderSource(fragmentShader, 1, &fragmentSource, NULL); glCompileShader(fragmentShader); // Link the vertex and fragment shader into a shader program GLuint shaderProgram = glCreateProgram(); glAttachShader(shaderProgram, vertexShader); glAttachShader(shaderProgram, fragmentShader); glLinkProgram(shaderProgram); glUseProgram(shaderProgram); // get uniform's id by name and set value GLint uRes = glGetUniformLocation(shaderProgram, "u_Resolution"); glUniform2f(uRes, 800.0f, 600.0f); // ---------------------------- RENDERING ------------------------------ // while(!glfwWindowShouldClose(window)) { // Clear the screen to black glClear(GL_COLOR_BUFFER_BIT); glClearColor(0.0f, 0.5f, 1.0f, 1.0f); // Draw a rectangle made of 2 triangles -> 6 vertices glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, NULL); // Swap buffers and poll window events glfwSwapBuffers(window); glfwPollEvents(); } // ---------------------------- CLEARING ------------------------------ // // Delete allocated resources glDeleteProgram(shaderProgram); glDeleteShader(fragmentShader); glDeleteShader(vertexShader); glDeleteBuffers(1, &vbo); glDeleteVertexArrays(1, &vao); return 0; }  
    • By Vortez
      Hi guys, im having a little problem fixing a bug in my program since i multi-threaded it. The app is a little video converter i wrote for fun. To help you understand the problem, ill first explain how the program is made. Im using Delphi to do the GUI/Windows part of the code, then im loading a c++ dll for the video conversion. The problem is not related to the video conversion, but with OpenGL only. The code work like this:

       
      DWORD WINAPI JobThread(void *params) { for each files { ... _ConvertVideo(input_name, output_name); } } void EXP_FUNC _ConvertVideo(char *input_fname, char *output_fname) { // Note that im re-initializing and cleaning up OpenGL each time this function is called... CGLEngine GLEngine; ... // Initialize OpenGL GLEngine.Initialize(render_wnd); GLEngine.CreateTexture(dst_width, dst_height, 4); // decode the video and render the frames... for each frames { ... GLEngine.UpdateTexture(pY, pU, pV); GLEngine.Render(); } cleanup: GLEngine.DeleteTexture(); GLEngine.Shutdown(); // video cleanup code... }  
      With a single thread, everything work fine. The problem arise when im starting the thread for a second time, nothing get rendered, but the encoding work fine. For example, if i start the thread with 3 files to process, all of them render fine, but if i start the thread again (with the same batch of files or not...), OpenGL fail to render anything.
      Im pretty sure it has something to do with the rendering context (or maybe the window DC?). Here a snippet of my OpenGL class:
      bool CGLEngine::Initialize(HWND hWnd) { hDC = GetDC(hWnd); if(!SetupPixelFormatDescriptor(hDC)){ ReleaseDC(hWnd, hDC); return false; } hRC = wglCreateContext(hDC); wglMakeCurrent(hDC, hRC); // more code ... return true; } void CGLEngine::Shutdown() { // some code... if(hRC){wglDeleteContext(hRC);} if(hDC){ReleaseDC(hWnd, hDC);} hDC = hRC = NULL; }  
      The full source code is available here. The most relevant files are:
      -OpenGL class (header / source)
      -Main code (header / source)
       
      Thx in advance if anyone can help me.
    • By DiligentDev
      This article uses material originally posted on Diligent Graphics web site.
      Introduction
      Graphics APIs have come a long way from small set of basic commands allowing limited control of configurable stages of early 3D accelerators to very low-level programming interfaces exposing almost every aspect of the underlying graphics hardware. Next-generation APIs, Direct3D12 by Microsoft and Vulkan by Khronos are relatively new and have only started getting widespread adoption and support from hardware vendors, while Direct3D11 and OpenGL are still considered industry standard. New APIs can provide substantial performance and functional improvements, but may not be supported by older hardware. An application targeting wide range of platforms needs to support Direct3D11 and OpenGL. New APIs will not give any advantage when used with old paradigms. It is totally possible to add Direct3D12 support to an existing renderer by implementing Direct3D11 interface through Direct3D12, but this will give zero benefits. Instead, new approaches and rendering architectures that leverage flexibility provided by the next-generation APIs are expected to be developed.
      There are at least four APIs (Direct3D11, Direct3D12, OpenGL/GLES, Vulkan, plus Apple's Metal for iOS and osX platforms) that a cross-platform 3D application may need to support. Writing separate code paths for all APIs is clearly not an option for any real-world application and the need for a cross-platform graphics abstraction layer is evident. The following is the list of requirements that I believe such layer needs to satisfy:
      Lightweight abstractions: the API should be as close to the underlying native APIs as possible to allow an application leverage all available low-level functionality. In many cases this requirement is difficult to achieve because specific features exposed by different APIs may vary considerably. Low performance overhead: the abstraction layer needs to be efficient from performance point of view. If it introduces considerable amount of overhead, there is no point in using it. Convenience: the API needs to be convenient to use. It needs to assist developers in achieving their goals not limiting their control of the graphics hardware. Multithreading: ability to efficiently parallelize work is in the core of Direct3D12 and Vulkan and one of the main selling points of the new APIs. Support for multithreading in a cross-platform layer is a must. Extensibility: no matter how well the API is designed, it still introduces some level of abstraction. In some cases the most efficient way to implement certain functionality is to directly use native API. The abstraction layer needs to provide seamless interoperability with the underlying native APIs to provide a way for the app to add features that may be missing. Diligent Engine is designed to solve these problems. Its main goal is to take advantages of the next-generation APIs such as Direct3D12 and Vulkan, but at the same time provide support for older platforms via Direct3D11, OpenGL and OpenGLES. Diligent Engine exposes common C++ front-end for all supported platforms and provides interoperability with underlying native APIs. It also supports integration with Unity and is designed to be used as graphics subsystem in a standalone game engine, Unity native plugin or any other 3D application. Full source code is available for download at GitHub and is free to use.
      Overview
      Diligent Engine API takes some features from Direct3D11 and Direct3D12 as well as introduces new concepts to hide certain platform-specific details and make the system easy to use. It contains the following main components:
      Render device (IRenderDevice  interface) is responsible for creating all other objects (textures, buffers, shaders, pipeline states, etc.).
      Device context (IDeviceContext interface) is the main interface for recording rendering commands. Similar to Direct3D11, there are immediate context and deferred contexts (which in Direct3D11 implementation map directly to the corresponding context types). Immediate context combines command queue and command list recording functionality. It records commands and submits the command list for execution when it contains sufficient number of commands. Deferred contexts are designed to only record command lists that can be submitted for execution through the immediate context.
      An alternative way to design the API would be to expose command queue and command lists directly. This approach however does not map well to Direct3D11 and OpenGL. Besides, some functionality (such as dynamic descriptor allocation) can be much more efficiently implemented when it is known that a command list is recorded by a certain deferred context from some thread.
      The approach taken in the engine does not limit scalability as the application is expected to create one deferred context per thread, and internally every deferred context records a command list in lock-free fashion. At the same time this approach maps well to older APIs.
      In current implementation, only one immediate context that uses default graphics command queue is created. To support multiple GPUs or multiple command queue types (compute, copy, etc.), it is natural to have one immediate contexts per queue. Cross-context synchronization utilities will be necessary.
      Swap Chain (ISwapChain interface). Swap chain interface represents a chain of back buffers and is responsible for showing the final rendered image on the screen.
      Render device, device contexts and swap chain are created during the engine initialization.
      Resources (ITexture and IBuffer interfaces). There are two types of resources - textures and buffers. There are many different texture types (2D textures, 3D textures, texture array, cubmepas, etc.) that can all be represented by ITexture interface.
      Resources Views (ITextureView and IBufferView interfaces). While textures and buffers are mere data containers, texture views and buffer views describe how the data should be interpreted. For instance, a 2D texture can be used as a render target for rendering commands or as a shader resource.
      Pipeline State (IPipelineState interface). GPU pipeline contains many configurable stages (depth-stencil, rasterizer and blend states, different shader stage, etc.). Direct3D11 uses coarse-grain objects to set all stage parameters at once (for instance, a rasterizer object encompasses all rasterizer attributes), while OpenGL contains myriad functions to fine-grain control every individual attribute of every stage. Both methods do not map very well to modern graphics hardware that combines all states into one monolithic state under the hood. Direct3D12 directly exposes pipeline state object in the API, and Diligent Engine uses the same approach.
      Shader Resource Binding (IShaderResourceBinding interface). Shaders are programs that run on the GPU. Shaders may access various resources (textures and buffers), and setting correspondence between shader variables and actual resources is called resource binding. Resource binding implementation varies considerably between different API. Diligent Engine introduces a new object called shader resource binding that encompasses all resources needed by all shaders in a certain pipeline state.
      API Basics
      Creating Resources
      Device resources are created by the render device. The two main resource types are buffers, which represent linear memory, and textures, which use memory layouts optimized for fast filtering. Graphics APIs usually have a native object that represents linear buffer. Diligent Engine uses IBuffer interface as an abstraction for a native buffer. To create a buffer, one needs to populate BufferDesc structure and call IRenderDevice::CreateBuffer() method as in the following example:
      BufferDesc BuffDesc; BufferDesc.Name = "Uniform buffer"; BuffDesc.BindFlags = BIND_UNIFORM_BUFFER; BuffDesc.Usage = USAGE_DYNAMIC; BuffDesc.uiSizeInBytes = sizeof(ShaderConstants); BuffDesc.CPUAccessFlags = CPU_ACCESS_WRITE; m_pDevice->CreateBuffer( BuffDesc, BufferData(), &m_pConstantBuffer ); While there is usually just one buffer object, different APIs use very different approaches to represent textures. For instance, in Direct3D11, there are ID3D11Texture1D, ID3D11Texture2D, and ID3D11Texture3D objects. In OpenGL, there is individual object for every texture dimension (1D, 2D, 3D, Cube), which may be a texture array, which may also be multisampled (i.e. GL_TEXTURE_2D_MULTISAMPLE_ARRAY). As a result there are nine different GL texture types that Diligent Engine may create under the hood. In Direct3D12, there is only one resource interface. Diligent Engine hides all these details in ITexture interface. There is only one  IRenderDevice::CreateTexture() method that is capable of creating all texture types. Dimension, format, array size and all other parameters are specified by the members of the TextureDesc structure:
      TextureDesc TexDesc; TexDesc.Name = "My texture 2D"; TexDesc.Type = TEXTURE_TYPE_2D; TexDesc.Width = 1024; TexDesc.Height = 1024; TexDesc.Format = TEX_FORMAT_RGBA8_UNORM; TexDesc.Usage = USAGE_DEFAULT; TexDesc.BindFlags = BIND_SHADER_RESOURCE | BIND_RENDER_TARGET | BIND_UNORDERED_ACCESS; TexDesc.Name = "Sample 2D Texture"; m_pRenderDevice->CreateTexture( TexDesc, TextureData(), &m_pTestTex ); If native API supports multithreaded resource creation, textures and buffers can be created by multiple threads simultaneously.
      Interoperability with native API provides access to the native buffer/texture objects and also allows creating Diligent Engine objects from native handles. It allows applications seamlessly integrate native API-specific code with Diligent Engine.
      Next-generation APIs allow fine level-control over how resources are allocated. Diligent Engine does not currently expose this functionality, but it can be added by implementing IResourceAllocator interface that encapsulates specifics of resource allocation and providing this interface to CreateBuffer() or CreateTexture() methods. If null is provided, default allocator should be used.
      Initializing the Pipeline State
      As it was mentioned earlier, Diligent Engine follows next-gen APIs to configure the graphics/compute pipeline. One big Pipelines State Object (PSO) encompasses all required states (all shader stages, input layout description, depth stencil, rasterizer and blend state descriptions etc.). This approach maps directly to Direct3D12/Vulkan, but is also beneficial for older APIs as it eliminates pipeline misconfiguration errors. With many individual calls tweaking various GPU pipeline settings it is very easy to forget to set one of the states or assume the stage is already properly configured when in fact it is not. Using pipeline state object helps avoid these problems as all stages are configured at once.
      Creating Shaders
      While in earlier APIs shaders were bound separately, in the next-generation APIs as well as in Diligent Engine shaders are part of the pipeline state object. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL. To create a shader, one needs to populate ShaderCreationAttribs structure. SourceLanguage member of this structure tells the system which language the shader is authored in:
      SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 mode, and GLSL for OpenGL and OpenGLES modes. SHADER_SOURCE_LANGUAGE_HLSL - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL and OpenGLES modes. There are two ways to provide the shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. Custom implementation can be provided when needed.
      When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a shader, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible. On older APIs, static samplers are emulated via generic sampler objects.
      The following is an example of shader initialization:
      ShaderCreationAttribs Attrs; Attrs.Desc.Name = "MyPixelShader"; Attrs.FilePath = "MyShaderFile.fx"; Attrs.SearchDirectories = "shaders;shaders\\inc;"; Attrs.EntryPoint = "MyPixelShader"; Attrs.Desc.ShaderType = SHADER_TYPE_PIXEL; Attrs.SourceLanguage = SHADER_SOURCE_LANGUAGE_HLSL; BasicShaderSourceStreamFactory BasicSSSFactory(Attrs.SearchDirectories); Attrs.pShaderSourceStreamFactory = &BasicSSSFactory; ShaderVariableDesc ShaderVars[] = {     {"g_StaticTexture", SHADER_VARIABLE_TYPE_STATIC},     {"g_MutableTexture", SHADER_VARIABLE_TYPE_MUTABLE},     {"g_DynamicTexture", SHADER_VARIABLE_TYPE_DYNAMIC} }; Attrs.Desc.VariableDesc = ShaderVars; Attrs.Desc.NumVariables = _countof(ShaderVars); Attrs.Desc.DefaultVariableType = SHADER_VARIABLE_TYPE_STATIC; StaticSamplerDesc StaticSampler; StaticSampler.Desc.MinFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MagFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MipFilter = FILTER_TYPE_LINEAR; StaticSampler.TextureName = "g_MutableTexture"; Attrs.Desc.NumStaticSamplers = 1; Attrs.Desc.StaticSamplers = &StaticSampler; ShaderMacroHelper Macros; Macros.AddShaderMacro("USE_SHADOWS", 1); Macros.AddShaderMacro("NUM_SHADOW_SAMPLES", 4); Macros.Finalize(); Attrs.Macros = Macros; RefCntAutoPtr<IShader> pShader; m_pDevice->CreateShader( Attrs, &pShader );
      Creating the Pipeline State Object
      After all required shaders are created, the rest of the fields of the PipelineStateDesc structure provide depth-stencil, rasterizer, and blend state descriptions, the number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:
      PipelineStateDesc PSODesc; RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; RasterizerDesc.AntialiasedLineEnable = False; Depth-stencil and blend states are defined in a similar fashion.
      Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:
      // Define input layout InputLayoutDesc &Layout = PSODesc.GraphicsPipeline.InputLayout; LayoutElement TextLayoutElems[] = {     LayoutElement( 0, 0, 3, VT_FLOAT32, False ),     LayoutElement( 1, 0, 4, VT_UINT8, True ),     LayoutElement( 2, 0, 2, VT_FLOAT32, False ), }; Layout.LayoutElements = TextLayoutElems; Layout.NumElements = _countof( TextLayoutElems ); Finally, pipeline state defines primitive topology type. When all required members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method:
      // Define shader and primitive topology PSODesc.GraphicsPipeline.PrimitiveTopologyType = PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; PSODesc.GraphicsPipeline.pVS = pVertexShader; PSODesc.GraphicsPipeline.pPS = pPixelShader; PSODesc.Name = "My pipeline state"; m_pDev->CreatePipelineState(PSODesc, &m_pPSO); When PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object. In case of Direct3D12 this maps directly to setting the D3D12 PSO object. In case of Direct3D11, this involves setting individual state objects (such as rasterizer and blend states), shaders, input layout etc. In case of OpenGL, this requires a number of fine-grain state tweaking calls. Diligent Engine keeps track of currently bound states and only calls functions to update these states that have actually changed.
      Binding Shader Resources
      Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command list. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:
      Static variables (SHADER_VARIABLE_TYPE_STATIC) are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. Mutable variables (SHADER_VARIABLE_TYPE_MUTABLE) define resources that are expected to change on a per-material frequency. Examples may include diffuse textures, normal maps etc. Dynamic variables (SHADER_VARIABLE_TYPE_DYNAMIC) are expected to change frequently and randomly. Shader variable type must be specified during shader creation by populating an array of ShaderVariableDesc structures and initializing ShaderCreationAttribs::Desc::VariableDesc and ShaderCreationAttribs::Desc::NumVariables members (see example of shader creation above).
      Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the shader object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:
      PixelShader->GetShaderVariable( "g_tex2DShadowMap" )->Set( pShadowMapSRV ); Mutable and dynamic variables are bound via a new Shader Resource Binding object (SRB) that is created by the pipeline state (IPipelineState::CreateShaderResourceBinding()):
      m_pPSO->CreateShaderResourceBinding(&m_pSRB); Note that an SRB is only compatible with the pipeline state it was created from. SRB object inherits all static bindings from shaders in the pipeline, but is not allowed to change them.
      Mutable resources can only be set once for every instance of a shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:
      m_pSRB->GetVariable(SHADER_TYPE_PIXEL, "tex2DDiffuse")->Set(pDiffuseTexSRV); In some cases it is necessary to bind a new resource to a variable every time a draw command is invoked. Such variables should be labeled as dynamic, which will allow setting them multiple times through the same SRB object:
      m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB objcet is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.
      As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.
      This post gives more details about the resource binding model in Diligent Engine.
      Setting the Pipeline State and Committing Shader Resources
      Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:
      m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
      The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
      Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
      m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
      Invoking Draw Command
      The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
      ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
      DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
      Source Code
      Full engine source code is available on GitHub and is free to use. The repository contains two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
      AntTweakBar sample is Diligent Engine’s “Hello World” example.

       
      Atmospheric scattering sample is a more advanced example. It demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

      Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

      Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

      Future Work
      The engine is under active development. It currently supports Windows desktop, Universal Windows and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
    • By michaeldodis
      I've started building a small library, that can render pie menu GUI in legacy opengl, planning to add some traditional elements of course.
      It's interface is similar to something you'd see in IMGUI. It's written in C.
      Early version of the library
      I'd really love to hear anyone's thoughts on this, any suggestions on what features you'd want to see in a library like this? 
      Thanks in advance!
  • Popular Now