Not sure what's going on here. Even with slightly smoothed normals I get this very odd white transition line at the start of the shadow area. Only when blurring the normals into oblivion, I end up with an acceptable transition from lighted to shadowed areas. Totally unacceptable shading result. 20.625 and standard surface shader. Distant light, but point and area lights deliver the same results. How can I avoid this? Is this a bug?
Cheers
Tom
Karma shading smooth surfaces
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- Tom Mangold
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Have you tried it in any other renderers? Looks like pretty standard shading to me... you'll notice sudden rate-of-curvature-changes like you have in the geometry here when you use a pure flat-colour shader. Not sure exactly how to apply the correct mathematical terms, but you'd want a smooth first-order-derivative of curvature (or something like that) to not spot the hint of discontinuity in the shading. That's essentially what you're getting if you blur the normals - you're smoothing over the rate-of-change.
It doesn't feel right, and looks wrong, but that's what you get when you switch from an arc to a dead-straight line, even if the tangent at the end of the arc matches the line. If you model in low poly and subdiv it all, you tend to avoid this look, because it'll naturally apply geometric falloff to such transitions, or you can just do what you've done, and blur the normals. You could even get clever and analyse the curvature, detect "edges" in the curvature values, and use those to selectively blur the normals...
It doesn't feel right, and looks wrong, but that's what you get when you switch from an arc to a dead-straight line, even if the tangent at the end of the arc matches the line. If you model in low poly and subdiv it all, you tend to avoid this look, because it'll naturally apply geometric falloff to such transitions, or you can just do what you've done, and blur the normals. You could even get clever and analyse the curvature, detect "edges" in the curvature values, and use those to selectively blur the normals...
Dan Wood
Vortex VFX Ltd
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- Tom Mangold
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Yeah, tried RS. Looks the same. The weird shadow transition - looks like an "even" grey part between light and shadow - is one thing, but the bright line shouldn't be there.
I can only imagine that shading and shadowing somehow add oddly up together in such a way, that the impression of the line appears. Very annoying subject and blurring needs to be quite high. Strength of 8 - 16 won't do. More like 500 - 1000, but this destroys the shape in many areas.
I'll give your curvature tip a go and see if this helps in any way. Thx for your thoughts.
P.S.: Tried out every setting in the renderer. Thought bias could make a difference, but it seems like it is not.
I can only imagine that shading and shadowing somehow add oddly up together in such a way, that the impression of the line appears. Very annoying subject and blurring needs to be quite high. Strength of 8 - 16 won't do. More like 500 - 1000, but this destroys the shape in many areas.
I'll give your curvature tip a go and see if this helps in any way. Thx for your thoughts.
P.S.: Tried out every setting in the renderer. Thought bias could make a difference, but it seems like it is not.
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- antc
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Like you said already there is no bright line (the pixel inspector doesn't report brighter pixels in that region) - your eye/brain is inventing it, making the discontinuous rate of change (derivative) in the normals along the seam more apparent than it really is. Bluring N is a reasonable way to go if you're unable to model the geometry with fewer polygons or as a subdivision surface.
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Thanks for the additional input.
Not sure how you projected the pattern. But if you look at the first mesh wireshaded you should see that it's "perfect". Straight lines which then go into a perfect half circle. So this pattern shouldn't be possible with the first mesh.
Just did it myself. The regular geo looks fine.
Not sure how you projected the pattern. But if you look at the first mesh wireshaded you should see that it's "perfect". Straight lines which then go into a perfect half circle. So this pattern shouldn't be possible with the first mesh.
Just did it myself. The regular geo looks fine.
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Tom Mangold
But if you look at the first mesh wireshaded you should see that it's "perfect".
Actually it's not 'perfect' - there is a difference of tangency where the curve parts and straight parts meet.
In order to lessen that quick transition there would have to be a gradual curving of the straight parts sooner.
A remeshing wouldn't change that even if you could.
If you really wanted to change it geometry wise, you would have to return to the original and remodel, introducing that curving sooner and more gradually. Or, just remodel in houdini using the existing geo as a base to work from.
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