Alternate the Triangles every Consequtive Row.

All right, I am noticing that the meshes for grids alternate the triangles directions every other row. What is the purpose for this?



“With communication we need understanding.” - JE

Could be to increase the Vertex Transform cache reuse, particularly if indexed triangles are being used here.
(Translation: To reduce the number of vertex shader executions required to render the mesh.)
I don’t know how wide your grids are in vertices. But do you notice the triangle serializing walking left and then right across a subset of the width rather than the full width?
If so, then it’s even more likely this was done to increase Vertex Transform cache reuse.

Here are a few fun blog posts by Tom Forsyth that explain: Strippers, Linear-Speed Vertex Cache Optimisation. Yes, it’s dated, but it still applies. However, on today’s GPUs, the size of the Vertex Transform cache (post-vertex shader) isn’t a fixed size but is sized dynamically (IIRC, based on the per-vertex varyings size and the amount of GPU shared memory available).

Also, looks like the OpenGL Wiki has a page about it: Post Transform Cache

Is it’s appearance any better, at all?


There shouldn’t be an appearance difference (if done properly). It’s a performance thing.