Rays from cycles often miss triangles (GPU and CPU) #34094

New Issue

Tobias Oelgarte · 2013-02-03T12:22:18+01:00

Tobias Oelgarte commented

2013-02-03 12:22:18 +01:00

%%%--- Operating System, Graphics card ---
Ubuntu 12.04 64 bit, GTX 560 TI

- Blender version with error ---

r54237

- Short description of error ---

Cycles misses triangles relatively often, which makes light shine trough walls, in between triangle edges. This is especially noticeable with a bright world background, which is seen trough a wall at the triangle intersections, even at relatively small scale (close to origin) and increases even further if objects are fruther away from the origin.

- Steps for others to reproduce the error (preferably based on attached .blend file) ---

I appended a simple example file with an icosphere and an emission shader which gives black for front side and white (10.0 due to multiplication with 10, just to make the samples more visible). Ideally there shouldn't be any white dots (rays that actually hit the backside of the sphere).

There is also a thread on blendpolis.de (with image and example file) in which the "light comes trough" the borders of a room: http://www.blendpolis.de/viewtopic.php?f=14&t=42853

%%%

%%%--- Operating System, Graphics card --- Ubuntu 12.04 64 bit, GTX 560 TI - Blender version with error --- r54237 - Short description of error --- Cycles misses triangles relatively often, which makes light shine trough walls, in between triangle edges. This is especially noticeable with a bright world background, which is seen trough a wall at the triangle intersections, even at relatively small scale (close to origin) and increases even further if objects are fruther away from the origin. - Steps for others to reproduce the error (preferably based on attached .blend file) --- I appended a simple example file with an icosphere and an emission shader which gives black for front side and white (10.0 due to multiplication with 10, just to make the samples more visible). Ideally there shouldn't be any white dots (rays that actually hit the backside of the sphere). There is also a thread on blendpolis.de (with image and example file) in which the "light comes trough" the borders of a room: http://www.blendpolis.de/viewtopic.php?f=14&t=42853 %%%

Tobias Oelgarte commented

2013-02-03 12:22:18 +01:00

Changed status to: 'Open'

Tobias Oelgarte commented

2013-02-03 12:33:02 +01:00

%%%I appended two additional screenshots:

ico-0.png shows the missing rays if the sphere is located at the origin.
ico-150.png shows the missing rays if the same sphere is located at x=150. There are quite a lot more rays missing the triangles.%%%

%%%I appended two additional screenshots: * ico-0.png shows the missing rays if the sphere is located at the origin. * ico-150.png shows the missing rays if the same sphere is located at x=150. There are quite a lot more rays missing the triangles.%%%

Tobias Oelgarte commented

2013-02-03 12:43:53 +01:00

%%%PS: The behavior of ico-150.png is especially noticeable if the preview is set to "Static BVH". If i use dynamic BVH, then the number of misses is more or less constant, even if moved to x=150.%%%

Thomas Dinges commented

2013-02-03 13:07:16 +01:00

%%%Confirmed the issue.

Assigning to Brecht. %%%

%%%Confirmed the issue. Assigning to Brecht. %%%

Brecht Van Lommel commented

2013-02-03 13:58:08 +01:00

%%%It's a float precision problem, some rays can slip through indeed. I don't consider this a bug, it would be good if we had a ray-triangle intersection that completely avoids such issues but it comes at a performance cost.%%%

Brecht Van Lommel commented

2013-02-03 13:58:08 +01:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2013-02-03 13:58:08 +01:00

Tobias Oelgarte commented

2013-02-03 14:05:08 +01:00

%%%I would not mind if it where "some rays", but with static BVH, which is also used for rendering it are a lot of rays. There must be more then a simple precession issue, because Dynamic BVH isn't affected that strongly.

It also ruins dark scenes with bright lights, because the lights simply go trough walls.%%%

%%%I would not mind if it where "some rays", but with static BVH, which is also used for rendering it are a lot of rays. There must be more then a simple precession issue, because Dynamic BVH isn't affected that strongly. It also ruins dark scenes with bright lights, because the lights simply go trough walls.%%%

Brecht Van Lommel commented

2013-02-03 16:02:44 +01:00

%%%I understand it can be problematic, the workaround is to create walls with some thickness. But this is a simple precision issue, static and dynamic BVH will cause the ray to be intersected in world and object space respectively, and one can be more precise than the other depending on the object transform and camera position.%%%

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Rays from cycles often miss triangles (GPU and CPU) #34094