Unfortunately, due to differences in polygon versus line
rasterization, a "less or equal" depth test will still produce z-fighting.
(You'd need the old SGI plane equation extension to make this work, to force
line line fragments to have Z values that match the polygon's plane equation.
Most hardware doesn't support this extension.)
Instead, I'd modify the algorithm below slightly: In the
second pass (when rendering in line mode), enable polygon offset to ensure
the lines don't z-fight with the polygon.
(As an additional note, this algorithm will only work if
you have polygonal geometry.)
Paul Martz
Skew Matrix Software
LLC
303 859 9466
The OSG does not have such a built-in feature afaik
Maybe you can draw your object in the z-buffer (disabling the color buffer output) and then draw the wireframe in the color buffer with a "less or equal" depth function.
Well, this is the approach I would use; implementing the technique described in the article seems very difficult, but it might be possible with a (very complex) shader.
Thibault
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