Hello,
Sorry for the late reply. I looked into it, and it is caused by a very specific combination of things in how the shading ("self-shadow") of the opening is calculated.
The shading method this object uses tries to make a transition between the shading of the curved surface and the shading of the vertical part. When calculating this transition, it takes the direction of the sun into consideration, and also the surface settings. The setting combination that causes this is the following:
- the direction of the sun (Azimuth) is 178º
- the Shininess of the surface is weak (should be around 40)
- the Specular of the surface is too strong (should be around 25)
If you just change the sun direction, it should work fine, but then if you set it to a problematic angle again, this might happen again. If you change the OpenGL surface settings, then it should be fine from now on. This only affects the OpenGL engine, so these setting changes should not affect rendered images.
I hope these suggestions help, and cleared things up a bit.
Regards,
Daniel Alexander Kovacs
Professional Services Consultant
GRAPHISOFT
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