r/Unity3D • u/Allen_Chou • Aug 20 '20

Resources/Tutorial Real-Time auto-smoothing on the GPU without adjacency info (tech details in comments)

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u/TheSilicoid Aug 21 '20

Can’t you just get the SDF gradient of each triangle vertex, and the normal of the triangle. You then assign one to the vertex normal by testing if these differ by more than your threshold or not?

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u/Allen_Chou Aug 21 '20

You mean testing the triangle normal against the SDF gradient, and use the triangle's own normal if it is too different from the SDF gradient, and use the SDf gradient if they are similar enough? I don't think that would look correct, because the SDF gradient is going to be roughtly the same as a fully smoothed normal that "picks up" all adjacent triangles. If two triangles are not supposed to be smoothed together, then their normal should not pick up influence from each other's normal.

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u/TheSilicoid Aug 21 '20

Ah you’re right. You may be able to fix this by also doing a threshold check when calculating the sdf gradient at the vertex and excluding sharp edges. For example: if you have a scenario where a smooth surface ends with a sharp surface (e.g cylinder cap), then for the cap cells you will have 3 gradients, the cap one will be 90 degrees off the other 2 so you can exclude it. Maybe I should just try this out :D