Smoke effected and occluded by Objects on separate Render Layers #39142

New Issue

David Brennan · 2014-03-12T20:52:35+01:00

David Brennan commented

2014-03-12 20:52:35 +01:00

System Information
Operating system and graphics card

Windows 7, 64-bit

Blender Version
Broken: (example: 2.69.7 4b206af, see splash screen)
Worked: (optional)

Blender 2.69 and 2.70 RC1

Short description of error

Smoke from the Smoke Domain gets occluded even by Objects which are on totally separate Render Layers. I have tried tweaking every setting I can think of, but there seems to be absolutely no solution for this.

Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps

Create a smoke via a Smoke Domain in Blender. Put this on Render Layer 1.
Put any other object inside that Smoke Domain - it can even be a transparent Object. Move that to Render Layer 2.
Go into the Compositor and render out the two separate Render Layers. You will see that the smoke on Render Layer 1 is being blocked by the dummy object on Render Layer 2.

I have attached a simple .Blend showing this.

SmokeCantBeIsolated.blend

**System Information** Operating system and graphics card Windows 7, 64-bit **Blender Version** Broken: (example: 2.69.7 4b206af, see splash screen) Worked: (optional) Blender 2.69 and 2.70 RC1 **Short description of error** Smoke from the Smoke Domain gets occluded even by Objects which are on totally separate Render Layers. I have tried tweaking every setting I can think of, but there seems to be absolutely no solution for this. **Exact steps for others to reproduce the error** Based on a (as simple as possible) attached .blend file with minimum amount of steps 1) Create a smoke via a Smoke Domain in Blender. Put this on Render Layer 1. 2) Put any other object inside that Smoke Domain - it can even be a transparent Object. Move that to Render Layer 2. 3) Go into the Compositor and render out the two separate Render Layers. You will see that the smoke on Render Layer 1 is being blocked by the dummy object on Render Layer 2. I have attached a simple .Blend showing this. [SmokeCantBeIsolated.blend](https://archive.blender.org/developer/F80869/SmokeCantBeIsolated.blend)

David Brennan commented

2014-03-12 20:52:35 +01:00

Changed status to: 'Open'

David Brennan commented

2014-03-12 20:52:35 +01:00

Added subscriber: @davidbrennan

Sergey Sharybin commented

2014-03-13 08:49:48 +01:00

Added subscriber: @Sergey

Sergey Sharybin commented

2014-03-13 08:50:19 +01:00

Added subscriber: @brecht

Sergey Sharybin commented

2014-03-13 08:50:19 +01:00

@brecht, for my knowledge volumes does not support layers, so it's rather a design limitation?

David Brennan commented

2014-03-13 10:49:33 +01:00

Because smoke would seem to frequently require modification - changing the color to brown or gray or green, depending upon the context - and because the Smoke Domains tend to be so large and interact with so many Objects, I am surprised that this issue has not come up very often.

Brecht Van Lommel commented

2014-03-13 14:37:42 +01:00

Objects on other render layers are supposed to influence the smoke for things like shadows or indirect light. The purpose of render layers is that you can recombine them to get the full image again with all inter object light interaction included. The only way to get them actually independent is to create a separate linked scene for rendering.

Further, it's impossible in general to separate transparent objects cleanly into render layers, there's not enough information in a pixel to do that, we would need to implement deep compositing to solve that.

Taking all that into account, it becomes a lot less clear what is supposed to happen here. In this particular case I think it could do better, but this system is in need of a rethinking, there are many known bugs here but no maintainer:
http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Render#Volume_Rendering

So, this moves to the to do list.

Objects on other render layers are supposed to influence the smoke for things like shadows or indirect light. The purpose of render layers is that you can recombine them to get the full image again with all inter object light interaction included. The only way to get them actually independent is to create a separate linked scene for rendering. Further, it's impossible in general to separate transparent objects cleanly into render layers, there's not enough information in a pixel to do that, we would need to implement deep compositing to solve that. Taking all that into account, it becomes a lot less clear what is supposed to happen here. In this particular case I think it could do better, but this system is in need of a rethinking, there are many known bugs here but no maintainer: http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Render#Volume_Rendering So, this moves to the to do list.

David Brennan commented

2014-03-13 14:39:59 +01:00

It would seem fairly simple, to me: Just make the Smoke Domain have the same "This Layer Only" option that lights have.

Brecht Van Lommel commented

2014-03-13 14:50:31 +01:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2014-03-13 14:50:31 +01:00

Brecht Van Lommel self-assigned this 2014-03-13 14:50:31 +01:00

Brecht Van Lommel commented

2014-03-13 14:50:31 +01:00

Adding new functionality to do what you expect it to do here is possible, though I'm not adding features to Blender Internal anymore. If you want them to be really independent you need to link the smoke object in a separate scene for now unless you can find a volunteer to implement that.

A "This Layer Only" option seems like it would be problematic though, one object causing another to be hidden inside it is going to be a problem for overlapping volumes and probably cached things like shadow maps or volume lighting.

Adding new functionality to do what you expect it to do here is possible, though I'm not adding features to Blender Internal anymore. If you want them to be really independent you need to link the smoke object in a separate scene for now unless you can find a volunteer to implement that. A "This Layer Only" option seems like it would be problematic though, one object causing another to be hidden inside it is going to be a problem for overlapping volumes and probably cached things like shadow maps or volume lighting.

Brecht Van Lommel removed their assignment 2014-03-13 14:50:42 +01:00

David Brennan commented

2014-03-13 20:31:25 +01:00

But smoke will still be generated in BI for the forseeable future, correct? (And note that, with Freestyle and some of the other functionality exclusive to BI, it's still probably in heavy use. For instance, I came across this problem when creating a simple "2.5D" photo animation, as inspired by this tutorial: http://blog.patdavid.net/2014/02/25d-parallax-animated-photo-tutorial.html. That is something that BI seems far better suited for than Cycles.)

Nevertheless, thank you for the thoughts, and I do indeed hope that somebody picks this up.

But smoke will still be generated in BI for the forseeable future, correct? (And note that, with Freestyle and some of the other functionality exclusive to BI, it's still probably in heavy use. For instance, I came across this problem when creating a simple "2.5D" photo animation, as inspired by this tutorial: http://blog.patdavid.net/2014/02/25d-parallax-animated-photo-tutorial.html. That is something that BI seems far better suited for than Cycles.) Nevertheless, thank you for the thoughts, and I do indeed hope that somebody picks this up.

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Smoke effected and occluded by Objects on separate Render Layers #39142