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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:


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.


“…Death is very likely the single best invention of Life.”

All the source code in the GLUT tutorial pages has been updated to be compatible with MacOS and Linux. As usual I might have missed something. Please do comment if you find a bug.

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.

Preston Blair

Preston Blair (1908-1995) was a Cartoon Animator who worked for Disney, MGM, Hanna-Barbera. He wrote many texts on the subject of cartoon animation, and  late in his life a book was published: “Cartoon Animation” that is sort of a compilation of all his work. The book is available for free in some websites, namely The book is also available from or


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..

Jason L. McKesson has completed a new section on his online book. This section covers Texturing.

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.


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