CODEWITHSUNDEEP
opengl
circlingthesun
circlingthesun

Reputation: 45

Pairwise vertex attributes in OpenGL

I'm trying to visualise a graph with OpenGL. I have vertex buffer with points in 3D space, and an index buffer that specifies lines between vertices. I use glDrawElements to draw the graph. Everything works. Problem is that I need to visualise the edge weights. My problem is that edge weights are pairwise attributes and I have no idea how to put this information into my shader. Only solutions I can think of is drawing each edge individually with DrawRangeElements and setting the edge weight between every call. Is there a better way of doing this?

Upvotes: 0

Views: 190

Answers (1)

Nicol Bolas
Nicol Bolas

Reputation: 473352

There's no need to employ a geometry shader. Just render them as GL_LINES, duplicating the positions as needed as well as providing the same "weight" attribute for each pair of verts on a line. This is ultimately no different from rendering a cube, where each face needs its own normals.

If (and only if) you absolutely must have that memory back, and you can't simply compress your vertex data (using normalized shorts, unnormalized shorts, or whatever), here are some techniques you can use. Be warned: this is a memory-vs-performance tradeoff. So unless you have real memory pressures, just duplicate your vertex data and get it over with.

Upvotes: 1

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