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Desa

OpenGL glPolygonOffset

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Does anyone know where I can find more information behind the math in OpenGL's glPolygonOffset routine? I have a 3D engine I use for mobile devices and I want to reproduce this function in my own code. Thanks. Here's the info about glPolygonOffset: http://www.opengl.org/resources/faq/technical/polygonoffset.htm#0020
Quote:
Polygon offset allows the application to specify a depth offset with two parameters, factor and units. factor scales the maximum Z slope, with respect to X or Y of the polygon, and units scales the minimum resolvable depth buffer value. The results are summed to produce the depth offset. This offset is applied in screen space, typically with positive Z pointing into the screen.

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Thanks! That's exactly what I was looking for.

I'm having some trouble with the equation (3.9). Do you know what the w subscript refers to when it talks about a point on the triangle (x,y,z) in the equation? It sounds like from the document that it's just a value from an arbitrary point, but the partial derivative of a number is always 0, so I'm not sure how to evaluate the equation.

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Thanks Eric. That helped a lot. How do you find the point inside the triangle? Also, does the del symbol in the equation (3.9) mean partial derivative or does it mean something else?

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