SSS + volume rendering error #39823

New Issue

gandalf3 · 2014-04-21T10:08:08+02:00

gandalf3 commented

2014-04-21 10:08:08 +02:00

System Information
Archlinux
Nvidia GTX 460

Blender Version
Broken: 0ed6725

Short description of error
Light emitted from volume/smoke emission does not travel inside materials with SSS though the smoke domain.

Exact steps for others to reproduce the error
Based on cycles_fire_SSS.blend

Open attached .blend
Play the animation up to about frame 60 (to simulate the fire up to a good point)
Look at the Sphere object with the rendered viewport. The SSS will have a sharp falloff at the border of the smoke domain.

**System Information** Archlinux Nvidia GTX 460 **Blender Version** Broken: 0ed6725 **Short description of error** Light emitted from volume/smoke emission does not travel inside materials with SSS though the smoke domain. **Exact steps for others to reproduce the error** Based on [cycles_fire_SSS.blend](https://archive.blender.org/developer/F85501/cycles_fire_SSS.blend) 1. Open attached .blend 2. Play the animation up to about frame 60 (to simulate the fire up to a good point) 3. Look at the `Sphere` object with the rendered viewport. The SSS will have a sharp falloff at the border of the smoke domain.

gandalf3 commented

2014-04-21 10:08:08 +02:00

Changed status to: 'Open'

gandalf3 commented

2014-04-21 10:08:08 +02:00

Added subscriber: @gandalf3

gandalf3 commented

2014-04-21 10:10:53 +02:00

Sorry about the poor title. I meant to say something like "Light emitted from fire does not scatter though the domain boundary", however the "Edit Task" button is disabled..

Brecht Van Lommel was assigned by Sergey Sharybin

2014-04-28 10:15:24 +02:00

Sergey Sharybin commented

2014-04-28 10:15:24 +02:00

Added subscriber: @Sergey

Brecht Van Lommel changed title from ~~volume/smoke emission will not be scattered outside the viewport~~ to SSS + volume rendering error

2014-05-05 16:02:39 +02:00

TS commented

2014-08-26 14:23:09 +02:00

Added subscriber: @underhood

Brecht Van Lommel was unassigned by Thomas Dinges

2014-09-03 00:46:02 +02:00

Sergey Sharybin was assigned by Thomas Dinges

2014-09-03 00:46:02 +02:00

Thomas Dinges commented

2014-09-03 00:46:02 +02:00

Added subscribers: @brecht, @ThomasDinges

Thomas Dinges commented

2014-09-03 00:46:02 +02:00

Sergey, maybe you have an idea?
This does not happen with a Diffuse shader, or a generic Volume Emission object, so it looks like directly related to the Domain.

Sergey, maybe you have an idea? This does not happen with a Diffuse shader, or a generic Volume Emission object, so it looks like directly related to the Domain.

Brecht Van Lommel commented

2014-09-03 02:43:07 +02:00

When SSS sampling is used to jump from one point on the surface to another, the volume stack is not updated. So if in jumping to another point on the surface a volume was entered or exited, that is not recorded properly.

It is possible to trace a ray between the original shading point and the SSS sampled shading point, and adjust the volume stack as needed (see e.g. the shadow tracing code for how to record the hits along a ray and loop over them updating the volume stack).

The problem is that this is going to introduce a slowdown. It's possible to skip this if there are no volumes at all in the scene of course.

When SSS sampling is used to jump from one point on the surface to another, the volume stack is not updated. So if in jumping to another point on the surface a volume was entered or exited, that is not recorded properly. It is possible to trace a ray between the original shading point and the SSS sampled shading point, and adjust the volume stack as needed (see e.g. the shadow tracing code for how to record the hits along a ray and loop over them updating the volume stack). The problem is that this is going to introduce a slowdown. It's possible to skip this if there are no volumes at all in the scene of course.

Sergey Sharybin commented

2014-09-18 13:19:58 +02:00

Created a patch for this issue D795.

Created a patch for this issue [D795](https://archive.blender.org/developer/D795).

blender-admin commented

2014-09-25 19:17:45 +02:00

This issue was referenced by ccc5983e2b

This issue was referenced by ccc5983e2bb87bde7b2895da6bea3fd129968aeb

Sergey Sharybin commented

2014-09-25 19:34:15 +02:00

Changed status from 'Open' to: 'Resolved'

Sergey Sharybin closed this issue