[webkit-dev] Accelerated 2D Tesselation Implementation

[Chris Marrin]

Hi Ken,

It would help me, and I think many others, if we could have a discussion of how exactly your tessellation logic works and what it is intended to do. For instance, is the algorithm you're using based on Loop-Blinn? I'm a bit familiar with that algorithm and some of the problems it has with rendering this type of geometry. For instance, there are typically anti-aliasing artifacts at the points where the interior triangles touch the edges. These are described in section 5.1 of the paper and the authors added additional (and not well described) logic to solve the problem. 

If you could describe your algorithm a bit and show some expected results with typical cases, that would be really helpful. 

For those not familiar with Loop-Blinn, here is a link to their original paper, presented at Siggraph 2005:

	Resolution Independent Curve Rendering using Programmable Graphics ...

It's a great algorithm for rendering resolution independent 2D objects using the GPU. It has potential to render both 2D shapes (as used in Canvas and SVG) and text glyphs. It's advantage is that once you generate the triangles for the shape, you can render the shape at any resolution. It's disadvantage is that the triangle generation is quite expensive, so mutating shapes can potentially be slower than a simpler resolution dependent tessellation.

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~Chris
cmarrin at apple.com




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