One of the bugs reported in here has been corrected. The uniform buffer data size is now reported correctly.
The other two bugs remain, unfortunately. Querying the primitive counter still gives zero, and glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS_ARB) still crashes the application.
Two more libs are available in the VS*L framework. With these new additions it is possible to use Assimp to load 3D models, and render them with core OpenGL. The libs store the meshes in VAOs, and use VSShaderLib and VSMathLib to simplify the rendering with shaders with almost any uniform variable configuration.
VSML has been renamed to VSMathLib. Too many libs in the pipeline to keep naming them with a single letter 
The M stood for Matrix, yet as now the library also contains vector operations, I think the new name fits better with the content.
Another addition is the availability of the normal and projection-view-model matrices. These are commonly used in shaders, and it doesn’t make sense to keep computing it for every vertex.
Finally, the lib now works with the VSShaderLib to provide a more general method for uniform variable settings.
Bug reports are most welcome.
Shaders are the core of the rendering process. OpenGL core profile requires us to provide our own shaders, no more fixed function.
Using shaders means more flexibility, but it also implies more work. This is where this lib steps in.
VSShaderLib was designed to make our life easier. It allows to create programs, load shaders from files, associate vertex attribute names with locations, and work with uniforms, including uniforms in named blocks. It also provides access to the info logs.
I don’t know where to put this. I’ve tried the AMD forum but got no reply. So here goes:
I’ve only tested this on Windows 7 64 bits. Anyone with different/same results on same or other systems?
- ARB Debug Output Extension
When not in debug mode the following instruction causes an Access Violation in Visual Studio:
glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS_ARB);
This only occurs when not in Debug OpenGL context and it does not cause any problem with nVidia hardware.
I’ve not tried it with Linux yet.
- Uniform Buffers
Consider a uniform block declared as follows:
layout (std140) uniform Matrices {
mat4 modelviewMatrix;
mat4 projModelViewMatrix;
mat3 normalMatrix[2];
};
This is what I get when I use glGetActiveUniformsiv to retrieve info on the block:
Matrices, Binding: 2 Datasize: 320 ActiveUniforms: 3 Referenced by: TessEval Shader(s) modelviewMatrix 1 16 mat4 0 normalMatrix 2 16 mat3 128 projModelViewMatrix 1 16 mat4 64
The data for each uniform is size, matrix stride, type and offset.
My problem lies with the size of the buffer. AMD’s driver claims, as shown above, that the size is 320, but in reality it is 224 (nVidia reports the right value), considering the reported matrix stride of 16. The math is pretty simple:
16×4 = 64 bytes for each 4×4 matrix times 2 = 128
16×3 = 48 bytes for each 3×3 matrix times 2 = 96
Total = 128 + 96 = 224.
Strangely enough, if I define the normalMatrix as an array with 3 mat3 (so one more than previously), I get a reported data size of 464.
I’ve tested several possibilities to set one of the mat3 without success. With nVidia it works OK . The only difference in the information reported, besides the data size, is the name of the normalMatrix uniform, that nVidia chooses to call it normalMatrix[0].
- Querying the primitive counter
I always get zero! Again works nicely in nVidia.
A page has been added to the GLUT Tutorial with all the source code and Visual Studio 2010 projects available to download. Check it out here.
FixStars has just released their OpenCL book online. This book has been available in Amazon and other stores and now its free. The sample code is also available..
Logging is one of those things that we keep doing when debugging. The Very Simple Log Library provides a very basic logging mechanism that can ouput to strings and files.
gDEBugger, by graphicRemedy, was a very powerful standalone tool (still available in here) for debugging OpenGL and OpenCL. It could tell you all about your VBOs, textures, uniform values, show stats on function calls, show deprecated usage function, you name it.
Now its back! This time it works inside Visual Studio 2010. It basically performs the same functions as before, but integrated in the programming environment of VS 2010.
The new AMD version is available in here.
Debugging is something we all do. It is one of those things we can’t escape…
Tools like Visual Studio are very powerful for debugging purposes and provide lots of debug options and information. However most of us don’t master these tools properly. If this is the case then you might want to take a look at this tutorial by Abhijit Jana.
