Negative-curvature spheres are shaded wrong #97

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opened 2025-07-15 06:47:51 +00:00 by Vectornaut · 1 comment

Vectornaut commented

2025-07-15 06:47:51 +00:00

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Expected behavior

Spheres are supposed to be shaded as follows:

There's a directional light from above the viewer's right shoulder, and also some ambient light.
Edges and intersections are highlighted.
When a sphere is selected, its surface brightens a little, and its edges brighten a lot.

You can see this shading by checking out pull request #85, loading the Empty test assembly, and adding a sphere.

Actual behavior

To reproduce the bug, flip the sphere from above inside out by setting its half-curvature to 0 and then to -0.5. This has the following effects:

The directional light appears to be reversed.
When the sphere is selected, its surface brightens far too much—perhaps as though the brightening that's meant for edges were being applied to the whole sphere.

### Expected behavior Spheres are supposed to be shaded as follows: - There's a directional light from above the viewer's right shoulder, and also some ambient light. - Edges and intersections are highlighted. - When a sphere is selected, its surface brightens a little, and its edges brighten a lot. You can see this shading by checking out pull request #85, loading the *Empty* test assembly, and adding a sphere. ### Actual behavior To reproduce the bug, flip the sphere from above inside out by setting its half-curvature to `0` and then to `-0.5`. This has the following effects: - The directional light appears to be reversed. - When the sphere is selected, its surface brightens far too much—perhaps as though the brightening that's meant for edges were being applied to the whole sphere.

Vectornaut added the

bug

labels 2025-07-15 06:47:51 +00:00

glen commented

2025-07-15 18:52:24 +00:00

Owner

Just want to register the concept that it is definitely OK for "inside-out" spheres to look different in some helpful way, to distinguish their orientation, but the current appearance is not helpful.