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OpenGL SDL. would YOU recommend it ?

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Hi folks, after quite a few problems with NeHe's basecode when resizing my opengl window on various different systems(esp Win7 grrrr) I had SDL recommended to me. It looks like a breeze to incorporate SDL and it's not only multi-platform but handles things like keyboard and mouse events too. However, development seems to be stalled from what I can see - which is a worry. 1.3 seems to be vaporware and I really don't like that it creates a DOS/Command window in addition to the main window. I'd be far happier going on the recommendation of people far more knowledgeable and experienced than me since I'm pretty new to opengl. All I'm looking for really is something that will handle the window management for me, the opengl is already pretty much complete. Opinions and advice greatly appreciated. Thanks.

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Quote:
Original post by FlyingSolo
I really don't like that it creates a DOS/Command window in addition to the main window.

This has nothing to do with SDL, it depends on your project settings (whether it's a console or Win32 subsystem).

Quote:

All I'm looking for really is something that will handle the window management for me, the opengl is already pretty much complete.

SDL is great for this task:

SDL_GL_SetAttribute(SDL_GL_xxx, vvv); // set the OpenGL attributes like VSync, double buffer, etc.
SDL_SetVideoMode(640, 480, 32, SDL_OPENGL);

while (running)
{
SDL_Event evt;
while (SDL_PollEvent(&evt)) /* handle events */;

// render GL stuff
SDL_GL_SwapBuffers();
}

That's all it takes to get GL running with SDL.

You might also want to look into SFML, which is very similar.

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SDL also runs in a tighter loop so its faster than the other predecessor window API's. It handles event for you, just use this code

SDL_Event event;

int main(int argc, char **argv)
{
while ( !quit )
{
while ( SDL_PollEvent(&event) )
{
if ( event.type == SDL_QUIT )
quit = true
if ( event.type == SDL_KEYDOWN )
{
if ( event.key.keysym.sym == SDLK_ESCAPE )
quit = true
}
}
}

SDL_Quit();
}


and also the init functions might look like this

bool Init(void)
{
if ( SDL_Init( SDL_INIT_VIDEO | SDL_INIT_TIMER ) < 0 )
return false;

if ( SDL_SetVideoMode( screenWidth, screenHeight, bitsperpixel, SDL_OPENGL | SDL_GL_DOUBLEBUFFER ) == NULL )
return false;

//setup opengl stuff
return true;
}

and the documentation is pretty easy to follow, such as the event struct and the keycodes

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SDL is a mature and capable library. Some big studios have used it when porting their games to Linux.

SDL 1.3 is available, you can build it and use it, for the "core" stuff it works. There are rough edges (particularly around the new features) and it does seem to be taking forever to get released, I would agree there. Then again these are volunteers contributing. I wouldn't classiffy it as vapourware though.

But yes, I would highly recommend SDL to accompany OpenGL.

And as nullsquared mentions, the console window is nothing to do with SDL.

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Yessir I'd recommend it. My current project utilizes SDL. My only personal issue with it is actually concerning SDL_net, which apparently is only usable for TCP communications, wheras my project uses the UDP protocol... thus I was forced to use winsock as I am comfortable incorporating it into my source.


I think you might get something out of checking out my engine 'method', WIP but it's opensource: www.van-noland.com

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You can use UDP with SDL_Net. That said, the sockets interface is virtually identical across all operating systems, so it doesn't buy you too much and it makes it hard to do some things (I don't believe it is possible to make a socket non-blocking, for instance).

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Well I guess that answered my question! Thank you all for some great replies.

But... with a very simple program I'm seeing memory usage increasing at about 4k/sec for no apparent reason.

Am I missing something with SDL? It seemed insanely easy to set up.

My wee test prog is below (error checking removed for some clarity). All this does is clear to yellow and draw a red quad.


#pragma comment(lib, "Glu32.lib")
#include &lt;windows.h&gt; #include &lt;stdio.h&gt; #include "SDL.h"
#include "SDL_opengl.h"

SDL_Surface* screen;
SDL_Event event;


void InitGL(void)
{
glClearColor( 1.0f, 1.0f, 0.0f, 0.0f );
glViewport( 0, 0, 800, 600 );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glOrtho(0.0f, 800, 600, 0.0f, -1.0f, 1.0f);
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
}


void Resize(GLsizei width, GLsizei height)
{
if (height==0) { height=1; } glViewport(0,0,width,height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glOrtho(0.0f, 800, 600, 0.0f, -1.0f, 1.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}


void DrawScene(void)
{
glColor4f(1.0f,0.0f,0.0f,1.0f);
glBegin(GL_QUADS);
glVertex2d(200,200);
glVertex2d(400,200);
glVertex2d(400,400);
glVertex2d(200,400);
glEnd();
}


int WINAPI WinMain( HINSTANCE hInstance, // Instance
HINSTANCE hPrevInstance, // Previous Instance
LPSTR lpCmdLine, // Command Line Parameters
int nCmdShow) // Window Show State
{
SDL_Init(SDL_INIT_VIDEO);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER,1);
screen = SDL_SetVideoMode(800,600,16,SDL_OPENGL | SDL_HWSURFACE | SDL_RESIZABLE);
InitGL();

while (1)
{
while( SDL_PollEvent( &event ) )
{
switch( event.type )
{
case SDL_KEYDOWN:
switch ( event.key.keysym.sym )
{
case SDLK_ESCAPE: exit(0); break;
default: break;
}
case SDL_VIDEORESIZE: //User resized window
screen = SDL_SetVideoMode(event.resize.w, event.resize.h, 16, SDL_OPENGL | SDL_HWSURFACE | SDL_RESIZABLE); // Create new window
Resize(event.resize.w, event.resize.h);
break; //Event handled, fetch next :)
case SDL_QUIT: exit (0); break;
default: break;
}
}
DrawScene();
SDL_GL_SwapBuffers();
SDL_Delay( 50 );
}

}


[Edited by - FlyingSolo on February 14, 2010 2:34:48 PM]

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The only thing I see right off is that you appear to be bypassing the SDL implementation of WinMain(). Without digging around a bit I couldn't tell you what the consequences of this would be, but I imagine it might cause some problems.

If you check out some SDL tutorials (the Lazy Foo tutorials are good, assuming you haven't already read them), you'll see that your typical SDL-based application has what appears to be a 'normal' main() function. There's actually some macros at work that allow SDL to create a 'main' function appropriate for the target platform and operating system, but you don't need to worry about that - just write main() as you would normally, and everything should work correctly. (Note that since in this context 'main' is actually a user-defined function, you must use the 'main' signature that matches what SDL expects, and you can't omit the return value as you could in a 'real' main function.)

Oh, and to get your code to format more nicely, you can use [ source ] tags (no spaces).

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I guess you are using WinMain function because of the additional console window.
As was said above: use a normal main function and add the following options to the Visual Studio's linker:
/SUBSYSTEM:WINDOWS
/ENTRY:mainCRTStartup
This will disable the additional console window.

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I recommend SDL + OpenGL. I use it for both OS X and Windows it has everything you need except for the platform specific stuff.

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Thank you one and all - excellent stuff, I've learned a lot.

Thanks for the heads up on the console, that's my inexperience with Visual C.

Tried setting up a new SDL project using Windows (/SUBSYSTEM:WINDOWS) but now I'm up to my armpits with msvcrt linker issues - I've seen these before and have no idea how to resolve them. Seems I'm not alone there though.

SDL apps have to be built as Multi-threaded DLL ? That means redisting the msvcr90.dll file with my app - that's new.

finally got a good handle on opengl, SDL is a breeze, it's the rotten compiler that's holding me up! Sometimes life just doesn't seem fair!

The Lazy Foo tut's don't work btw (msvcrt errors as above) which is a shame. Guess they're for 2005 not 2008.

More to learn - thanks all.

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Qt Logo

I recommend dropping SDL and similar libraries in favor of Qt. It is free, cross platform, it has excellent documentation and it is in active development. It provides you with much much more that SDL. Especially with a complete GUI library and a high level hardware accelerated painting engine.

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Quote:
Original post by FlyingSolo
SDL apps have to be built as Multi-threaded DLL ? That means redisting the msvcr90.dll file with my app - that's new.

Yes, unless you rebuild SDL with another option.
Quote:

More to learn - thanks all.

My exact settings for compiling with SDL on MSVC2008 are:
SDLmain.lib
SDL.lib
(in that order)
/SUBSYSTEM:CONSOLE in linker command line settings
int main(int argc, char **argv) for the main function

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Once again - thanks to all! Although google is an invaluable tool these days, there is no substitute for people with real experience. I really do appreciate your help. I know us relative newbies are a pain in the ass !

All seems to be working happily with SDL now although I did have some fun with some demo code I found. Pressing the ALT key would cause the app to resize to something like 32767x100 :) Sorted now thank God.

I did look at Qt briefly a while back, I think it would be like using the entire 101st Airborne to break up a bar fight though. My app, although complex, is relatively small. I've bookmarked that though for future projects though.

Thanks for the MSVC tips, always very useful to have. I've been using Delphi since v1.0 and boy does that spoil you. You can give no thought whatsoever to setup and just concentrate on your code - it really does rock. (but I love C !)

Big thanks to M$ for making Visual C a freebie, but as with most modern software it's bloated and there are more options and tweaks than I could shake a sh1tty stick at! I started on DEC PDP-8i's about 30 years ago and it was a lot less complex then!

So, for now - it all seems happy again, and my goal of getting this running on the Mac and possibly Linux too has been made easier by SDL - and you guys.

Thank you all ! :-)

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Quote:
Original post by FlyingSolo
I'd be far happier going on the recommendation of people far more knowledgeable and experienced than me since I'm pretty new to opengl.



I've used SDL for a long time now and have recently started folding OpenGL into my SDL programming experience.

I've used Allegro (back in the day), SFML, and tinkered around with DirectX. SDL is the most intuitive and best documented of all the libraries I've used. Combined with OpenGL, you can get some pretty fast graphics in place with lucid audio and user input handling.

SDL has several child projects that help round it off more thoroughly. SDL_image is pretty much necessary for me because I tend to store my sprites in a format other than .BMP. SDL_ttf is a bit obnoxious and I just defer to OpenGL for showing text. SDL_mixer is rather necessary and not very hard to learn.

I've never bothered with socket programming so I can't comment on SDL_net.

In short, I'd recommend SDL. It's portable and it just plain works. Maybe I'm just too dumb but I never could get SDLdotNET (the C# wrapper for SDL) or SFML to really work for me and DirectX gives me ulcers. I've gotten the best results in the least amount of time with good, old-fashioned SDL projects.

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On an interesting note, the Palm Pre will be using SDL as its official graphics library with the release of the native programming SDK. As a Pre owner, I found that interesting.

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SDL is a jack of all trades and a master of none.

For example of the lack of optimization, I complained on the mailing list that "SDL_SemWait() on Windows calls WaitForSingleObject(), which obtains a kernel lock all of the time and thus has significant overhead even when it returns right away--from an Intel forum, it's about 40 times slower than a user-space lock. It would make sense to change this to only call when the program actually expects it to block. A user-space lock should be done using interlocked operations similar to the way it's in pthreads-win32, then WFSO called if it has to wait." then I was told to make a change myself I felt it necessary. I used pthreads instead and specialized substitutes can be optimally selected to replace all other aspects of SDL as well.

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@Prune

It is much a volunteer project. If you have taken the time to do this research, and go so far as to tell them what the problem is and how it could be fixed, why not fix it? Thus this issue would no longer exist.

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Quote:
Original post by Ectara
@Prune

It is much a volunteer project. If you have taken the time to do this research, and go so far as to tell them what the problem is and how it could be fixed, why not fix it? Thus this issue would no longer exist.
Prune's example isn't the only one, and while his is a relatively technical issue, some of the others aren't.

A personal gripe of mine: we have been waiting since sometime in 2003 for the SDL_WM_ToggleFullScreen() function to be implemented outside of linux. The function has been in the API all this time, but somehow, it never quite is implemented...

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I really like FreeGLUT. Its under active development and really simple, its designed to work with OpenGL from the start, AND it works with OpenGL 3.0. I like it a lot.

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Quote:
Original post by Steve132
I really like FreeGLUT. Its under active development and really simple, its designed to work with OpenGL from the start, AND it works with OpenGL 3.0. I like it a lot.
Another worthy choice is glfw-lite, unfortunately only available from the subversion repository. Basically, they stripped all the cruft (threading, image loading, etc.) out of glfw, and updated it considerably.

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Quote:
Original post by FlyingSolo
Hi folks,
after quite a few problems with NeHe's basecode when resizing my opengl window on various different systems(esp Win7 grrrr) I had SDL recommended to me.


I've never touched SDL. However, I have been using OpenGL for many years. I would really recommend that you try and get the base code working, if for no other reason than understanding how to implement an OpenGL context fully in Windows. I'm using OpenGL under Windows 7 and have had no trouble with it at all.

SDL may be the best thing for your project; I simply do not know. However, using it to avoid learning how / having to solve a problem will only cause you headaches in the future.

Also, the NeHe tutorials are not the best way to get started. They have caused me a great deal of frustration. Many of them are poorly written and the Windows code is horrible. When I was starting to learn Windows programming a couple of years ago, I made the mistake of trying to use the NeHe examples. I ended up getting more information and understanding out of a 10 year old Windows 95 game programming book.

Exactly what problems are you having?

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I like SFML because it is a bit more modular than SDL. In terms of window management and input events, it is pretty much identical to SDL, but you have the ability to link just the system and window libraries and just leave out all the crap you don't need, like the sprite system, sound, and networking to help keep your namespaces uncluttered.

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      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 tutorials, sample applications, asteroids performance benchmark and an example Unity project that uses Diligent Engine in native plugin.
      Atmospheric scattering sample 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, Linux, Android, MacOS, and iOS platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and Metal backend is in the plan.
    • By LifeArtist
      Good Evening,
      I want to make a 2D game which involves displaying some debug information. Especially for collision, enemy sights and so on ...
      First of I was thinking about all those shapes which I need will need for debugging purposes: circles, rectangles, lines, polygons.
      I am really stucked right now because of the fundamental question:
      Where do I store my vertices positions for each line (object)? Currently I am not using a model matrix because I am using orthographic projection and set the final position within the VBO. That means that if I add a new line I would have to expand the "points" array and re-upload (recall glBufferData) it every time. The other method would be to use a model matrix and a fixed vbo for a line but it would be also messy to exactly create a line from (0,0) to (100,20) calculating the rotation and scale to make it fit.
      If I proceed with option 1 "updating the array each frame" I was thinking of having 4 draw calls every frame for the lines vao, polygons vao and so on. 
      In addition to that I am planning to use some sort of ECS based architecture. So the other question would be:
      Should I treat those debug objects as entities/components?
      For me it would make sense to treat them as entities but that's creates a new issue with the previous array approach because it would have for example a transform and render component. A special render component for debug objects (no texture etc) ... For me the transform component is also just a matrix but how would I then define a line?
      Treating them as components would'nt be a good idea in my eyes because then I would always need an entity. Well entity is just an id !? So maybe its a component?
      Regards,
      LifeArtist
    • By QQemka
      Hello. I am coding a small thingy in my spare time. All i want to achieve is to load a heightmap (as the lowest possible walking terrain), some static meshes (elements of the environment) and a dynamic character (meaning i can move, collide with heightmap/static meshes and hold a varying item in a hand ). Got a bunch of questions, or rather problems i can't find solution to myself. Nearly all are deal with graphics/gpu, not the coding part. My c++ is on high enough level.
      Let's go:
      Heightmap - i obviously want it to be textured, size is hardcoded to 256x256 squares. I can't have one huge texture stretched over entire terrain cause every pixel would be enormous. Thats why i decided to use 2 specified textures. First will be a tileset consisting of 16 square tiles (u v range from 0 to 0.25 for first tile and so on) and second a 256x256 buffer with 0-15 value representing index of the tile from tileset for every heigtmap square. Problem is, how do i blend the edges nicely and make some computationally cheap changes so its not obvious there are only 16 tiles? Is it possible to generate such terrain with some existing program?
      Collisions - i want to use bounding sphere and aabb. But should i store them for a model or entity instance? Meaning i have 20 same trees spawned using the same tree model, but every entity got its own transformation (position, scale etc). Storing collision component per instance grats faster access + is precalculated and transformed (takes additional memory, but who cares?), so i stick with this, right? What should i do if object is dynamically rotated? The aabb is no longer aligned and calculating per vertex min/max everytime object rotates/scales is pretty expensive, right?
      Drawing aabb - problem similar to above (storing aabb data per instance or model). This time in my opinion per model is enough since every instance also does not have own vertex buffer but uses the shared one (so 20 trees share reference to one tree model). So rendering aabb is about taking the model's aabb, transforming with instance matrix and voila. What about aabb vertex buffer (this is more of a cosmetic question, just curious, bumped onto it in time of writing this). Is it better to make it as 8 points and index buffer (12 lines), or only 2 vertices with min/max x/y/z and having the shaders dynamically generate 6 other vertices and draw the box? Or maybe there should be just ONE 1x1x1 cube box template moved/scaled per entity?
      What if one model got a diffuse texture and a normal map, and other has only diffuse? Should i pass some bool flag to shader with that info, or just assume that my game supports only diffuse maps without fancy stuff?
      There were several more but i forgot/solved them at time of writing
      Thanks in advance
    • By RenanRR
      Hi All,
      I'm reading the tutorials from learnOpengl site (nice site) and I'm having a question on the camera (https://learnopengl.com/Getting-started/Camera).
      I always saw the camera being manipulated with the lookat, but in tutorial I saw the camera being changed through the MVP arrays, which do not seem to be camera, but rather the scene that changes:
      Vertex Shader:
      #version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; out vec2 TexCoord; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { gl_Position = projection * view * model * vec4(aPos, 1.0f); TexCoord = vec2(aTexCoord.x, aTexCoord.y); } then, the matrix manipulated:
      ..... glm::mat4 projection = glm::perspective(glm::radians(fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); ourShader.setMat4("projection", projection); .... glm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp); ourShader.setMat4("view", view); .... model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f)); ourShader.setMat4("model", model);  
      So, some doubts:
      - Why use it like that?
      - Is it okay to manipulate the camera that way?
      -in this way, are not the vertex's positions that changes instead of the camera?
      - I need to pass MVP to all shaders of object in my scenes ?
       
      What it seems, is that the camera stands still and the scenery that changes...
      it's right?
       
       
      Thank you
       
    • By dpadam450
      Sampling a floating point texture where the alpha channel holds 4-bytes of packed data into the float. I don't know how to cast the raw memory to treat it as an integer so I can perform bit-shifting operations.

      int rgbValue = int(textureSample.w);//4 bytes of data packed as color
      // algorithm might not be correct and endianness might need switching.
      vec3 extractedData = vec3(  rgbValue & 0xFF000000,  (rgbValue << 8) & 0xFF000000, (rgbValue << 16) & 0xFF000000);
      extractedData /= 255.0f;
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