How do I prevent jagged edges from appearing along the surfaces of my 3d model?
Let's say I have implemented a crude shaded model viewer in openGL that displays a series of blocks, so I have something similar to this.
Whenever I turn my model to the side, it causes an unwanted jagged effect along any surface with a steep viewing angle.
I'm sure this is due to the polygon offset I used to prevent z-battles between model and wireframe, however I cannot find the factor / unit parameters in openGL that prevent this unwanted effect.
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What are the best factor and unit values for glPolygonOffset to prevent this?
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will implement anti-aliasing to fix the problem? is this performance tradeoff trivial / meaningful?
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Could it be a shading issue? should i try a solution along this line of thought?
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It doesn't look like a Z fight to me.
If you draw flat shaded objects and then some GL_LINES over it, those lines will create this effect because they are not anti-aliased.
Why not just apply a mesh texture to your objects? This way you can use OpenGL texture filtering. You may try:
- Enable filtering MIN_ and MAG_ on this texture.
- Create a texture with mipmaps using gluBuild2DMipmaps. (see Creating Mipmaps )
- Enable Anisotropic Filtering? (see this page )
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Most likely you get a z-battle at steep corners (i.e. when all points have very similar z-values) because
1) You have too bad a resolution for the z-buffer if you set a 16-bit z-buffer - try change resolution to 32-bit
2) Your model is very small and all your points are too close together. You can try expanding the model.
Using a fixed offset will give inconsistent results because most z-buffer circuits are biased to provide a higher resolution the closer you are to the closest plane of the clip. ie you need less offset the closer you are to the plane of the nearest clip.
Here's a gamedev article that goes into more detail
Note that anti-aliasing and changing shaders is unlikely to help you here (unless you made some funky custom pixel shader to modulate z values, but that seems overkill to me, although I'm not an expert on pixel / fragment shaders so it can be doable)
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