Mirrored objects render black with Blender Internal #44102

New Issue

Aaron Corey · 2015-03-23T18:22:31+01:00

Aaron Corey commented

2015-03-23 18:22:31 +01:00

System Information

Occurs on 2 systems (both Windows 8.1). One system has a Geforce GTX745 card, and the other has an Intel integrated HD 4600 graphics.

Blender Version

Broken: Bug occurs on 2.73a and 2.74RC2
Worked: works on 2.69

Description

When a duplicated mesh object has been mirrored (with the object shading is set to smooth and auto-smooth enabled), the Blender Internal renderer renders the object completely black.

Exact steps for others to reproduce the error

Add a UV Sphere and add a new material
Set shading to smooth
Enable auto smooth
Create a linked duplicate (Alt-D) and place it beside the original sphere
Mirror the duplicate about an axis (For example: Object > Mirror > X Global)
Press F12 to render

The original object renders normally, but the duplicate renders as black. Even if the original object is deleted, and then the normals are recalculated on the second (remaining) object, it still renders as black. This bug appears to have similar symptoms as #40014 and #41079, which were previously fixed.

test.blend

**System Information** Occurs on 2 systems (both Windows 8.1). One system has a Geforce GTX745 card, and the other has an Intel integrated HD 4600 graphics. **Blender Version** Broken: Bug occurs on 2.73a and 2.74RC2 Worked: works on 2.69 **Description** When a duplicated mesh object has been mirrored (with the object shading is set to smooth and auto-smooth enabled), the Blender Internal renderer renders the object completely black. **Exact steps for others to reproduce the error** 1. Add a UV Sphere and add a new material 2. Set shading to smooth 3. Enable auto smooth 4. Create a linked duplicate (Alt-D) and place it beside the original sphere 5. Mirror the duplicate about an axis (For example: Object > Mirror > X Global) 6. Press F12 to render The original object renders normally, but the duplicate renders as black. Even if the original object is deleted, and then the normals are recalculated on the second (remaining) object, it still renders as black. This bug appears to have similar symptoms as #40014 and #41079, which were previously fixed. [test.blend](https://archive.blender.org/developer/F154467/test.blend)

Aaron Corey commented

2015-03-23 18:22:31 +01:00

Changed status to: 'Open'

Aaron Corey commented

2015-03-23 18:22:31 +01:00

Added subscriber: @AaronCorey

Aaron Corey commented

2015-03-23 18:38:36 +01:00

I should also mention that I discovered a work-around for this issue. If you make the duplicate object single-user and then apply the scale (Object > Apply > Scale), the object will then render properly. But of course, you lose the benefit of linked duplicates if you do that. I assume that applying the scale works because mirroring the object is essentially the same as scaling it by -1 along an axis?

Julian Eisel commented

2015-03-23 19:39:46 +01:00

Added subscribers: @mont29, @JulianEisel

Julian Eisel commented

2015-03-23 19:39:46 +01:00

Can confirm this. Turning off "Auto Smooth" or scaling by -1/mirroring again "solves" it. It also happens for every other object with a scale < 0 [Edit: and Auto Smooth enabled]. I bet Auto Smooth doesn't like negative scales... @mont29, maybe you can have a look? Might even be related to you custom normals work.

Can confirm this. ![black_uv_sphere_bug.png](https://archive.blender.org/developer/F154503/black_uv_sphere_bug.png) Turning off "Auto Smooth" or scaling by -1/mirroring again "solves" it. It also happens for every other object with a scale < 0 [Edit: and Auto Smooth enabled]. I bet Auto Smooth doesn't like negative scales... @mont29, maybe you can have a look? Might even be related to you custom normals work.

Bastien Montagne was assigned by Julian Eisel

2015-03-23 19:40:00 +01:00

Campbell Barton commented

2015-03-23 20:07:54 +01:00

Added subscriber: @ideasman42

Campbell Barton commented

2015-03-23 20:07:55 +01:00

Caused by 776f8d5a6f, assigning to @mont29

Caused by 776f8d5a6f, assigning to @mont29

Aaron Corey commented

2015-03-23 20:12:26 +01:00

I did a little more testing to narrow down the version where the change occurred. 2.70a renders mirrored objects correctly, but 2.71 renders them black.