OpenGL 4 Shading Language Cookbook - Third Edition

How to do it...

In the OpenGL program, after linking the shader program, use the following steps to assign data to the uniform block in the fragment shader:

1. Get the index of the uniform block using glGetUniformBlockIndex:

GLuint blockIndex = glGetUniformBlockIndex(programHandle,    "BlobSettings");

2. Allocate space for the buffer to contain the data for the uniform block. We get the size using glGetActiveUniformBlockiv:

GLint blockSize; 
glGetActiveUniformBlockiv(programHandle, blockIndex,        GL_UNIFORM_BLOCK_DATA_SIZE, &blockSize); 
 
GLubyte * blockBuffer; 
blockBuffer = (GLubyte *) malloc(blockSize); 

3. Query for the offset of each variable within the block. To do so, we first find the index of each variable within the block:

const GLchar *names[] ...