OpenGL: Single vertex attribute for multiple vertices?

Question

I have a vertex shader that accepts the following attributes:

• a_posCoord: vertex position
• a_texCoord: texture coordinate (passed

Answer 1

A vertex is not a position A vertex is a long vector consisting of multiplie attributes. Change one single attribute and you end up with a different vertex. So no, you can not use a single vertex attribute for multiple vertices, because that makes no sense semantically.

However what is possible with newer versions of OpenGL is setting the rate at which a certain vertex attribute's buffer offset advances. Effectively this means that the data for a given vertex array gets duplicated to n vertices before the buffer offset for a attribute advances. The function to set this divisor is glVertexAttribDivisor. In your case you'd set a Binding Divisor of 6 for the alpha array. But it's important that this does not use a single attribute for multiple vertices, but it makes OpenGL do that duplication you were doing for you.