CODEWITHSUNDEEP
3dopengl-es-2.0
seahorse
seahorse

Reputation: 2470

OpenGL ES 2.0 - passing modelview mat4 as attribute variable

To implement Geometry instancing in OpenGL ES 2.0 I am considering passing mat4 as an attribute. Since attributes are per vertex data do I need to pass this same mat4, three times for each vertex of the same triangle(since modelview remains constant across vertices of the triangle).

That would amount to a lot of extra data sent to the GPU( 2 extra vertices*16 floats*(Number of triangles) amount of extra data).

Or should I be sending the mat4 only once per triangle?But how is that possible using attributes since attributes are defined as "per vertex" data?

Upvotes: 1

Views: 328

Answers (1)

Tim
Tim

Reputation: 35943

There's no such thing as a 'per-triangle' attribute. If you want to send them as attributes, it's per vertex.

Another option would be to upload all matrices in a uniform array, and then just have an integer index per vertex which determines which matrix to lookup. That will reduce your streaming overhead by quite a bit.

Upvotes: 2

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