• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
Chris_F

OpenGL
TexSubImage2D performance

7 posts in this topic

I was curious to see the performance of texture uploads with my configuration using OpenGL and noticed something I think is odd. I create a 4K texture using glTexStorage2D with one MIP level and a format of GL_RGBA8. Then, every frame I use glTexSubImage2D to re-upload a static image buffer to the texture. Based off the frame rate I get about 5.19GB/s. Next, I changed the format of the texture to GL_SRGB8_ALPHA8 and re-try the experiment. This time I am getting 2.81GB/s, a significant decrease. This seems odd because as far as I know there shouldn't be anything different about uploading sRGB data verses uploading RGB data, as there is no conversion that should be taking place (sRGB conversion takes place in the shader, during sampling).

 

Some additional information. All I'm rendering is a fullscreen quad with a pixel shader that simply outputs vec4(1), I'm not even sampling from the texture or doing anything else each frame other than calling glTexSubImage2D. For the first test I use GL_RGBA and GL_UNSIGNED_INT_8_8_8_8_REV in the call to glTexSubImage2D, as this is what the driver tells me is ideal. For the second test I use GL_UNSIGNED_INT_8_8_8_8, as per the drivers suggestion. A bit of testing confirms that these are the fastest formats to use respectively. This is using an Nvidia GPU.

1

Share this post


Link to post
Share on other sites

Are both source and destination SRGB?

 

Edit - just to clarify - by one mip level do you mean you're only using mip0, rather than mip0 & mip1.

Edited by mark ds
0

Share this post


Link to post
Share on other sites

Are both source and destination SRGB?

 

Edit - just to clarify - by one mip level do you mean you're only using mip0, rather than mip0 & mip1.

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <vector>
#include <cstdlib>
#include <cstdio>

#define SCREEN_SIZE_X 1024
#define SCREEN_SIZE_Y 1024

#define GLSL(src) "#version 440 core\n" #src

const char* vertex_shader = GLSL(
    const vec2 data[4] = vec2[]
    (
        vec2(-1.0,  1.0),
        vec2(-1.0, -1.0),
        vec2( 1.0,  1.0),
        vec2( 1.0, -1.0)
    );

    void main()
    {
        gl_Position = vec4(data[gl_VertexID], 0.0, 1.0);
    }
);

const char* fragment_shader = GLSL(
    layout(location = 0) uniform sampler2D texture0;
    layout(location = 1) uniform vec2 screenSize;
    out vec4 frag_color;

    void main()
    {
        frag_color = texture(texture0, gl_FragCoord.xy / screenSize);
    }
);

int main(int argc, char *argv[])
{
    if(!glfwInit())
        exit(EXIT_FAILURE);

    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 4);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

    GLFWwindow* window = glfwCreateWindow(SCREEN_SIZE_X, SCREEN_SIZE_Y, "OpenGL Texture Upload", nullptr, nullptr);

    if(!window)
    {
        glfwTerminate();
        exit(EXIT_FAILURE);
    }

    glfwMakeContextCurrent(window);
    glfwSwapInterval(0);

    glewExperimental = GL_TRUE;

    if(glewInit() != GLEW_OK)
    {
        glfwTerminate();
        exit(EXIT_FAILURE);
    }
    
    GLuint vao = 0;
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);

    GLuint vs = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vs, 1, &vertex_shader, nullptr);
    glCompileShader(vs);

    GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fs, 1, &fragment_shader, nullptr);
    glCompileShader(fs);

    GLuint shader_program = glCreateProgram();
    glAttachShader(shader_program, fs);
    glAttachShader(shader_program, vs);
    glLinkProgram(shader_program);
    glUseProgram(shader_program);

    glProgramUniform2f(shader_program, 1, SCREEN_SIZE_X, SCREEN_SIZE_Y);

    GLuint texture = 0;
    glGenTextures(1, &texture);
#ifdef USE_SRGB
    glTextureStorage2DEXT(texture, GL_TEXTURE_2D, 1, GL_SRGB8_ALPHA8, 4096, 4096);
#else
    glTextureStorage2DEXT(texture, GL_TEXTURE_2D, 1, GL_RGBA8, 4096, 4096);
#endif
    glTextureParameteriEXT(texture, GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTextureParameteriEXT(texture, GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTextureParameteriEXT(texture, GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTextureParameteriEXT(texture, GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glBindMultiTextureEXT(GL_TEXTURE0, GL_TEXTURE_2D, texture);
    glProgramUniform1i(shader_program, 0, 0);

    std::vector<unsigned int> image_buffer(4096*4096, 0xFF0000FFul);

    double lastTime = glfwGetTime();
    double nbFrames = 0;

    while(!glfwWindowShouldClose(window))
    {
        double currentTime = glfwGetTime();
        nbFrames++;
        if (currentTime - lastTime >= 1.0)
        {
            char cbuffer[50];
            snprintf(cbuffer, sizeof(cbuffer), "OpenGL Texture Upload [%.1f fps, %.3f ms]", nbFrames, 1000.0 / nbFrames);
            glfwSetWindowTitle(window, cbuffer);
            nbFrames = 0;
            lastTime++;
        }
#ifdef USE_SRGB
        glTextureSubImage2DEXT(texture, GL_TEXTURE_2D, 0, 0, 0, 4096, 4096, GL_RGBA, GL_UNSIGNED_INT_8_8_8_8, image_buffer.data());
#else
        glTextureSubImage2DEXT(texture, GL_TEXTURE_2D, 0, 0, 0, 4096, 4096, GL_RGBA, GL_UNSIGNED_INT_8_8_8_8_REV, image_buffer.data());
#endif
        glClear(GL_COLOR_BUFFER_BIT);
        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glfwDestroyWindow(window);
    glfwTerminate();
    exit(EXIT_SUCCESS);
}
0

Share this post


Link to post
Share on other sites

Seems OK - I was guessing some internal conversion between SRGB & RGB.

 

However, GL_UNSIGNED_INT_8_8_8_8 vs GL_UNSIGNED_INT_8_8_8_8_REV stands out as a likely candidate...

0

Share this post


Link to post
Share on other sites

Seems OK - I was guessing some internal conversion between SRGB & RGB.

 

However, GL_UNSIGNED_INT_8_8_8_8 vs GL_UNSIGNED_INT_8_8_8_8_REV stands out as a likely candidate...

 

I used glGetInternalformativ to find the optimum pixel format for each internal format. As I said, experimental testing confirms that no other pixel format is faster for these respective formats, so no matter what, uploading sRGB is always slower than uploading RGB. As for internal conversion, as I said, that should not be the case. If it were, that would be horrendous.

Edited by Chris_F
0

Share this post


Link to post
Share on other sites

with one MIP level

This could be the problem. Refering to its specification , it is possible, that your texture (-parts) will be converted into linear RGB first, then downsampled and converted back to sRGB afterwards. Take a look at the specification (marked it with *):

 

 24) How should mipmap generation work for sRGB textures?

        RESOLVED:  The best way to perform mipmap generation for sRGB
        textures is by downsampling the sRGB image in a linear color
        space.

*        This involves converting the RGB components of sRGB texels
*        in a given texture image level to linear RGB space, filtering
*        appropriately in that linear RGB space, and then converting the
*        linear RGB values to sRGB for storage in the downsampled texture
*        level image.

        (Remember alpha, when present, is linear even in sRGB texture
        formats.)

        The OpenGL specification says "No particular filter algorithm
        is required, though a box filter is recommended as the default
        filter" meaning there is no requirement for how even non-sRGB
        mipmaps should be generated.  So while the resolution to this
        issue is technically a recommendation, it is however a strongly
        advised recommendation.

        The rationale for why sRGB textures should be converted to
        linear space prior to filtering and converted back to sRGB after
        filtering is clear.  If an implementation naively simply performed
        linear filtering on (non-linear) sRGB components as if they were
        in a linear space, the result tends to be a subtle darkening of
        the texture images as mipmap generation continues recursively.
        This darkening is an inappropriate basis that the resolved
        "best way" above would avoid.
Edited by Ashaman73
0

Share this post


Link to post
Share on other sites

here is no conversion that should be taking place (sRGB conversion takes place in the shader, during sampling).

Some additional information. All I'm rendering is a fullscreen quad with a pixel shader that simply outputs vec4(1), I'm not even sampling from the texture or doing anything else

 

This, however, looks like you are:

frag_color = texture(texture0, gl_FragCoord.xy / screenSize);

 

 

Maybe it is the actual sampling that slows you down, not the texture upload.

 

Can you, instead of measuring frame time, use a timer query (and maybe a fence sync) so you really measure glTexImage2D?

0

Share this post


Link to post
Share on other sites


This could be the problem. Refering to its specification , it is possible, that your texture (-parts) will be converted into linear RGB first, then downsampled and converted back to sRGB afterwards. Take a look at the specification (marked it with *):

 

That should not be the case. I create the texture through the glTexStorage API, asking for only 1 MIP level, which means that I get an immutable texture that only has room for one MIP level. The driver wouldn't (shouldn't) be calculating MIPs on a texture that can't store them. Experimentation with textureLod confirms that there are no other MIPs present.

 


Maybe it is the actual sampling that slows you down, not the texture upload.



Can you, instead of measuring frame time, use a timer query (and maybe a fence sync) so you really measure glTexImage2D?

 

I suppose I could give it a try (I have not used those features before), however my intuition tells me that the cost of doing sRGB conversion for a single texture on a single quad at 1024x1024 screen resolution is going to be negligible. Also, I modified it so that I only uploaded the texture once and then simply drew the quad each frame, and in that scenario there is no difference in performance for sRGB or RGB.

0

Share this post


Link to post
Share on other sites

OK, can anyone actually help me measure this correctly. No matter what, the result of a timer query seems to be the same, about 0.001056ms.

 

For example, if I do this:

GLuint query;
glGenQueries(1, &query);
glBeginQuery(GL_TIME_ELAPSED, query);

for(int i = 0; i < 100; ++i) {
    glTextureSubImage2DEXT(texture, GL_TEXTURE_2D, 0, 0, 0, 8192, 8192, GL_RGBA, GL_UNSIGNED_INT_8_8_8_8_REV, image_buffer.data());
}

glEndQuery(GL_TIME_ELAPSED);
GLuint elapsed_time;
glGetQueryObjectuiv(query, GL_QUERY_RESULT, &elapsed_time);
glDeleteQueries(1, &query);
float time_ms = elapsed_time / 1000000.0f;
printf("time: %f ms\n", time_ms);

It will take many seconds to complete and yet still 0.001056ms is printed.

Edited by Chris_F
0

Share this post


Link to post
Share on other sites

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  
Followers 0

  • Similar Content

    • By Toastmastern
      So it's been a while since I took a break from my whole creating a planet in DX11. Last time around I got stuck on fixing a nice LOD.
      A week back or so I got help to find this:
      https://github.com/sp4cerat/Planet-LOD
      In general this is what I'm trying to recreate in DX11, he that made that planet LOD uses OpenGL but that is a minor issue and something I can solve. But I have a question regarding the code
      He gets the position using this row
      vec4d pos = b.var.vec4d["position"]; Which is then used further down when he sends the variable "center" into the drawing function:
      if (pos.len() < 1) pos.norm(); world::draw(vec3d(pos.x, pos.y, pos.z));  
      Inside the draw function this happens:
      draw_recursive(p3[0], p3[1], p3[2], center); Basically the 3 vertices of the triangle and the center of details that he sent as a parameter earlier: vec3d(pos.x, pos.y, pos.z)
      Now onto my real question, he does vec3d edge_center[3] = { (p1 + p2) / 2, (p2 + p3) / 2, (p3 + p1) / 2 }; to get the edge center of each edge, nothing weird there.
      But this is used later on with:
      vec3d d = center + edge_center[i]; edge_test[i] = d.len() > ratio_size; edge_test is then used to evaluate if there should be a triangle drawn or if it should be split up into 3 new triangles instead. Why is it working for him? shouldn't it be like center - edge_center or something like that? Why adding them togheter? I asume here that the center is the center of details for the LOD. the position of the camera if stood on the ground of the planet and not up int he air like it is now.

      Full code can be seen here:
      https://github.com/sp4cerat/Planet-LOD/blob/master/src.simple/Main.cpp
      If anyone would like to take a look and try to help me understand this code I would love this person. I'm running out of ideas on how to solve this in my own head, most likely twisted it one time to many up in my head
      Thanks in advance
      Toastmastern
       
       
    • By fllwr0491
      I googled around but are unable to find source code or details of implementation.
      What keywords should I search for this topic?
      Things I would like to know:
      A. How to ensure that partially covered pixels are rasterized?
         Apparently by expanding each triangle by 1 pixel or so, rasterization problem is almost solved.
         But it will result in an unindexable triangle list without tons of overlaps. Will it incur a large performance penalty?
      B. A-buffer like bitmask needs a read-modiry-write operation.
         How to ensure proper synchronizations in GLSL?
         GLSL seems to only allow int32 atomics on image.
      C. Is there some simple ways to estimate coverage on-the-fly?
         In case I am to draw 2D shapes onto an exisitng target:
         1. A multi-pass whatever-buffer seems overkill.
         2. Multisampling could cost a lot memory though all I need is better coverage.
            Besides, I have to blit twice, if draw target is not multisampled.
       
    • By mapra99
      Hello

      I am working on a recent project and I have been learning how to code in C# using OpenGL libraries for some graphics. I have achieved some quite interesting things using TAO Framework writing in Console Applications, creating a GLUT Window. But my problem now is that I need to incorporate the Graphics in a Windows Form so I can relate the objects that I render with some .NET Controls.

      To deal with this problem, I have seen in some forums that it's better to use OpenTK instead of TAO Framework, so I can use the glControl that OpenTK libraries offer. However, I haven't found complete articles, tutorials or source codes that help using the glControl or that may insert me into de OpenTK functions. Would somebody please share in this forum some links or files where I can find good documentation about this topic? Or may I use another library different of OpenTK?

      Thanks!
    • By Solid_Spy
      Hello, I have been working on SH Irradiance map rendering, and I have been using a GLSL pixel shader to render SH irradiance to 2D irradiance maps for my static objects. I already have it working with 9 3D textures so far for the first 9 SH functions.
      In my GLSL shader, I have to send in 9 SH Coefficient 3D Texures that use RGBA8 as a pixel format. RGB being used for the coefficients for red, green, and blue, and the A for checking if the voxel is in use (for the 3D texture solidification shader to prevent bleeding).
      My problem is, I want to knock this number of textures down to something like 4 or 5. Getting even lower would be a godsend. This is because I eventually plan on adding more SH Coefficient 3D Textures for other parts of the game map (such as inside rooms, as opposed to the outside), to circumvent irradiance probe bleeding between rooms separated by walls. I don't want to reach the 32 texture limit too soon. Also, I figure that it would be a LOT faster.
      Is there a way I could, say, store 2 sets of SH Coefficients for 2 SH functions inside a texture with RGBA16 pixels? If so, how would I extract them from inside GLSL? Let me know if you have any suggestions ^^.
    • By KarimIO
      EDIT: I thought this was restricted to Attribute-Created GL contexts, but it isn't, so I rewrote the post.
      Hey guys, whenever I call SwapBuffers(hDC), I get a crash, and I get a "Too many posts were made to a semaphore." from Windows as I call SwapBuffers. What could be the cause of this?
      Update: No crash occurs if I don't draw, just clear and swap.
      static PIXELFORMATDESCRIPTOR pfd = // pfd Tells Windows How We Want Things To Be { sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor 1, // Version Number PFD_DRAW_TO_WINDOW | // Format Must Support Window PFD_SUPPORT_OPENGL | // Format Must Support OpenGL PFD_DOUBLEBUFFER, // Must Support Double Buffering PFD_TYPE_RGBA, // Request An RGBA Format 32, // Select Our Color Depth 0, 0, 0, 0, 0, 0, // Color Bits Ignored 0, // No Alpha Buffer 0, // Shift Bit Ignored 0, // No Accumulation Buffer 0, 0, 0, 0, // Accumulation Bits Ignored 24, // 24Bit Z-Buffer (Depth Buffer) 0, // No Stencil Buffer 0, // No Auxiliary Buffer PFD_MAIN_PLANE, // Main Drawing Layer 0, // Reserved 0, 0, 0 // Layer Masks Ignored }; if (!(hDC = GetDC(windowHandle))) return false; unsigned int PixelFormat; if (!(PixelFormat = ChoosePixelFormat(hDC, &pfd))) return false; if (!SetPixelFormat(hDC, PixelFormat, &pfd)) return false; hRC = wglCreateContext(hDC); if (!hRC) { std::cout << "wglCreateContext Failed!\n"; return false; } if (wglMakeCurrent(hDC, hRC) == NULL) { std::cout << "Make Context Current Second Failed!\n"; return false; } ... // OGL Buffer Initialization glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT); glBindVertexArray(vao); glUseProgram(myprogram); glDrawElements(GL_TRIANGLES, indexCount, GL_UNSIGNED_SHORT, (void *)indexStart); SwapBuffers(GetDC(window_handle));  
  • Popular Now