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# Objective Avoid a premature normalize operation and get better smooth normals for it. ## Inspiration @IceSentry suggested `face_normal()` could have its normalize removed based on [this article](https://iquilezles.org/articles/normals/) in PR #16039. ## Solution I did not want to change `face_normal()` to return a vector that's not normalized. The name "normal" implies it'll be normalized. Instead I added the `face_area_normal()` function, whose result is not normalized. Its magnitude is equal two times the triangle's area. I've noted why this is the case in its doc comment. I changed `compute_smooth_normals()` from computing normals from adjacent faces with equal weight to use the area of the faces as a weight. This has the benefit of being cheaper computationally and hopefully produces better normals. The `compute_flat_normals()` is unchanged and still uses `face_normal()`. ## Testing One test was added which shows the bigger triangle having an effect on the normal, but the previous test that uses the same size triangles is unchanged. **WARNING:** No visual test has been done yet. No example exists that demonstrates the compute_smooth_normals(). Perhaps there's a good model to demonstrate what the differences are. I would love to have some input on this. I'd suggest @IceSentry and @stepancheg to review this PR. ## Further Considerations It's possible weighting normals by their area is not definitely better than unweighted. It's possible there may be aesthetic reasons to prefer one over the other. In such a case, we could offer two variants: weighted or unweighted. Or we could offer another function perhaps like this: `compute_smooth_normals_with_weights(|normal, area| 1.0)` which would restore the original unweighted sum of normals. --- ## Showcase Smooth normal calculation now weights adjacent face normals by their area. ## Migration Guide |
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