What is the difference between Constant Vertex Attributes and Uniforms?

Posted by Samaursa on Game Development See other posts from Game Development or by Samaursa
Published on 2012-11-19T15:41:00Z Indexed on 2012/11/19 17:24 UTC
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opengl

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glsl

According to the OpenGL ES 2.0 Programming Guide:

A constant vertex attribute is the same for all vertices of a primitive, and 
therefore only one value needs to be specified for all the vertices of a 
primitive.

For uniforms the book states:

...any parameter to a shader that is constant across either all vertices or 
fragments (but that is not known at compile time) should be passed in as 
a uniform.

I've always used uniforms for data that is constant for a primitive but now it appears that attributes can also be used in the same way. Is there more to constant vertex attribute than simply 'they are the same as uniforms'?

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