Cycles renders black object with smooth shading and negative scale #49310

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Tautvydas Andrikys · 2016-09-09T13:53:53+02:00

2016-09-09 13:53:53 +02:00

Cycles renders black object with smooth shading and negative scale. Earlier was similar bug reports in Blender itself, but now this happens in Cycles.

I have managed to trace back and can offer possible fix:

in src/kernel/geom/geom_triangle.h, function triangle_smooth_normal you should invert normal vector if it is negative scale:

normalize((1.0f - u - v)*n2 + u*n0 + v*n1) => -normalize((1.0f - u - v)*n2 + u*n0 + v*n1)

Cycles renders black object with smooth shading and negative scale. Earlier was similar bug reports in Blender itself, but now this happens in Cycles. I have managed to trace back and can offer possible fix: in src/kernel/geom/geom_triangle.h, function triangle_smooth_normal you should invert normal vector if it is negative scale: ``` normalize((1.0f - u - v)*n2 + u*n0 + v*n1) => -normalize((1.0f - u - v)*n2 + u*n0 + v*n1) ```

Tautvydas Andrikys commented

2016-09-09 13:53:53 +02:00

Changed status to: 'Open'

Tautvydas Andrikys commented

2016-09-09 13:53:53 +02:00

Added subscriber: @esminis

Sergey Sharybin was assigned by Bastien Montagne

2016-09-09 14:11:35 +02:00

Brecht Van Lommel commented

2016-09-11 16:38:30 +02:00

Added subscriber: @brecht

Brecht Van Lommel commented

2016-09-11 16:38:30 +02:00

I can't reproduce this issue, please provide all the information requested in the instructions , with .blend file, Blender version, etc.

We already have some code to handle cases like this, see usage of transform_negative_scale.

I can't reproduce this issue, please provide all the information requested in the [instructions ](https://developer.blender.org/maniphest/task/edit/form/1/), with .blend file, Blender version, etc. We already have some code to handle cases like this, see usage of `transform_negative_scale`.

Tautvydas Andrikys commented

2016-09-12 06:59:10 +02:00

I always reproduce it but only on cycles alone (not on whole blender), here is project file project.xml and I use command

bin/cycles project.xml

I always reproduce it but only on cycles alone (not on whole blender), here is project file [project.xml](https://archive.blender.org/developer/F358317/project.xml) and I use command ``` bin/cycles project.xml ```

Tautvydas Andrikys commented

2016-09-23 11:08:44 +02:00

Did you manage to reproduce this issue?

blender-admin commented

2016-09-25 05:07:38 +02:00

This issue was referenced by blender/cycles@9c512fd0b6

This issue was referenced by blender/cycles@9c512fd0b6ff07c26e4a3507abd5c8dac816ad01

blender-admin commented

2016-09-25 05:07:38 +02:00

This issue was referenced by 335ee5ce5a

This issue was referenced by 335ee5ce5aee3a92415d1608cc66acf3da995598

Brecht Van Lommel commented

2016-09-25 05:26:27 +02:00

Changed status from 'Open' to: 'Resolved'

Brecht Van Lommel closed this issue

2016-09-25 05:26:27 +02:00

Brecht Van Lommel commented

2016-09-25 05:28:18 +02:00

Should be fixed now, we didn't notice this was broken since we get the normals Blender from usually. The issue was that both the face normal and vertex normal were being flipped, which cancels each other out.

The fix is in the Blender repo, that gets synced into the Cycles repo at some point.

Should be fixed now, we didn't notice this was broken since we get the normals Blender from usually. The issue was that both the face normal and vertex normal were being flipped, which cancels each other out. The fix is in the Blender repo, that gets synced into the Cycles repo at some point.

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Cycles renders black object with smooth shading and negative scale #49310