Object with z scale of 0 appears black at certain angles
Closed, ArchivedPublic

Description

System Information
Operating system: Linux Mint 18.1
Graphics card: lspci shows: VGA compatible controller: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor Integrated Graphics Controller (rev 06)
(Note: It looks like I'm only able to use CPU rendering, so this is probably irrelevant.)

Blender Version
Broken:

  • Linux Mint stable build 2.76b with "unkown" hash
  • latest build 2.79b f4dc9f9d68b
  • test build 2.79 0a8af46707a

Worked: None

Short description of error

The scene contains one square with a white diffuse material. There is a camera in front of it and a light in front of the camera. It should appear white, but when rendered appears completely black.

Exact steps for others to reproduce the error

To reproduce, just render and see that the square is black when it should be white.

Any one of the following actions will fix the error:

  • Rotate slightly: Just select the square and type r x -5, and re-render.
  • Render in 3D view: Just type numpad-0 and shift-z to change 3D view to render mode. This should be the same as the final render (right?) but is white while the final render is black.
  • Remove the z scale: Type 'n' and go to Transform -> Scale, set z to 1, and re-render.

(For context, I was following the tutorial at https://www.youtube.com/watch?v=T70ia5GMmzo and the bug was happening for the clock face. So this bug probably did not exist when the tutorial was created.)

Details

Type
Bug

Can confirm the behavior, not sure though if there is a reasonable fix.

Regarding the viewport: its only fine with Dynamic BVH, Static BVH also has this problem.

There were related reports T30929, T35200, T45778 and T46322 (with a bit more info on why this happens [degenerate matrix]).

As a workaround you can also just apply the scale to your object (Ctrl+A > Scale) which would leave you with the exact same result [no need to alter rotate or scale]

We should get @Brecht Van Lommel (brecht) and/or @Sergey Sharybin (sergey) onboard to decide whether this is a known limitation or something that should be fixed...

Philipp Oeser (lichtwerk) triaged this task as Normal priority.Jun 20 2018, 10:14 AM
Brecht Van Lommel (brecht) closed this task as Archived.Jul 1 2018, 9:05 PM

While it may be possible to improve this, in general objects with zero scale and multiple faces in the same plane can't be expected to render correctly in Cycles and most other renderers.

For now I would not consider this a bug, but something we could look to improve once.