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Thread: A Look At OpenGL ES 3.0: Lots Of Good Stuff

  1. #11
    Join Date
    Sep 2012


    Quote Originally Posted by curaga View Post
    Vert packing is an old trick, you can create any complex system you like as long as you can also unpack in a vertex shader.

    You sure it will be a benefit though?
    How can a vertex shader look at more than one vertex at a time? With delta compression, every vertex would depend on the previous one, so the GPU could not unpack them in parallel. However multiple delta-compressed sequences could be unpacked in parallel. So maybe each vertex given could be the start of a delta-compressed path, and a supplementary buffer provides the deltas? But a vertex shader is restricted to producing one output vertex for each input vertex. What I want is a way to generate vertices in shader code. Bezier rendering is adaptive: you generate more vertices in the areas of the curve which make tight bends, and fewer in the areas which are closer to straight; so it's hard to predict the total number that you need in advance. When rendering delta-compressed sequences, the total number of output vertices can be known in advance, however it's still a vertex-generation problem because each vertex must be visited in order, to apply diffs from the previous vertex. Isn't this type of problem the point of having geometry shaders?

  2. #12
    Join Date
    Feb 2008


    Yes, delta compression in general is badly parallelizable. But you may be able to send the vertices as 8-bit values still with clever packing, in non-delta ways.

    I was only talking about your point of sending less data over. Geometry shaders are needed to generate more, I agree there.

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