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edwinnie

image based silhouette detector?

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hey, jus wondering, are there any imaged based edge detectors that are suitable for silhouettes? esp those that are used in the pixel shaders. thx! Edwinz

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What exactly are you aiming on doing? I've read some academic papers on shadow removal in images, but that's pretty hardcore computer vision stuff. I'm no expert on pixel shaders, so I'm not sure what you are wanting the edge detectors for.

If you want any academic papers, then Google Scholar is a good first point of call. At the very least, the papers you find there will cite the really good papers with the theory you need.

Edit: Ah, I think I misunderstood. I thought you wanted to detect the shadows, not draw them, which on a second reading (and the post below) might be what you were asking. If so, sorry!

[Edited by - Trapper Zoid on August 4, 2005 6:00:08 AM]

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ya, I can't see any image level edge detection algorithm working, it's just to slow for one thing, and it's not possible to be 100 percent accurate with that stuff. silouetes are drawn by looking at the normal of the triangle rendered relative to the view vector, like backface culling

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Guest Anonymous Poster
i thought that ATI shipped a demo with their systems that had toon rendering with an image based edge detection algorithm?

http://www.ati.com/developer/demos/r9700.html

i thought it was the NPR demo on this page (1/2 way down, with the fruit and wine?)

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Have you looked at the Post-Processing sample in the DirectX SDK? Their normal edge detection shader works quite nicely. It works by rendering the mesh with a normal map shader and then using that normal edge detect shader to compute the actual images. If you are looking to compute just the outline then a simple color edge detect would be enough, but you need to apply it on a mesh with uniform colors for it to be effective.

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