Graphics Reference
In-Depth Information
• The maximum available storage per uniform buffer can be queried
using
glGetInteger64v
with
GL_MAX_UNIFORM_BLOCK_SIZE
, which
returns the size in bytes. The minimum supported number for any
implementation is 16 KB.
If you violate any of these limits, the program will fail to link.
The following example shows how to set up a uniform buffer object with
the named uniform block
LightTransform
described earlier:
GLuint blockId, bufferId;
GLint blockSize;
GLuint bindingPoint = 1;
GLfloat lightData[] =
{
// lightDirection (padded to vec4 based on std140 rule)
1.0f, 0.0f, 0.0f, 0.0f,
// lightPosition
0.0f, 0.0f, 0.0f, 1.0f
};
// Retrieve the uniform block index
blockId = glGetUniformBlockIndex ( program, “LightBlock” );
// Associate the uniform block index with a binding point
glUniformBlockBinding ( program, blockId, bindingPoint );
// Get the size of lightData; alternatively,
// we can calculate it using sizeof(lightData) in this example
glGetActiveUniformBlockiv ( program, blockId,
GL_UNIFORM_BLOCK_DATA_SIZE,
&blockSize );
// Create and fill a buffer object
glGenBuffers ( 1, &bufferId );
glBindBuffer ( GL_UNIFORM_BUFFER, bufferId );
glBufferData ( GL_UNIFORM_BUFFER, blockSize, lightData,
GL_DYNAMIC_DRAW);
// Bind the buffer object to the uniform block binding point
glBindBufferBase ( GL_UNIFORM_BUFFER, bindingPoint, buffer );
In addition to querying for uniform information on the program object,
you will need to use the program object to set up vertex attributes.
The queries for vertex attributes are very similar to the uniform
