Cycles is not rendering direct light with volumetrics, only indirect (builds from buildbot after 2.71). 2.71 renders are ok) #40987

New Issue

Piotr Rogowski · 2014-07-08T00:42:01+02:00

Piotr Rogowski commented

2014-07-08 00:42:01 +02:00

System Information
Lenovo Y580 Intel Core i7-3630QM CPU, 15,6 GiB RAM, Nvidia GeForce GTX 660M (GK107M), Linux Mint 17 64-bit
Blender Version
Broken: Blender 2.71 from buildbot (Hash 4299b00) (and several earlier versions)
Worked: Blender 2.71 stable (Hash: 9337574)
Short description of error
Cycles is not rendering direct light with volumetrics, only indirect.
Exact steps for others to reproduce the error
Just starting with the default cube, add to it Object/quick effects/quick smoke, Add a volume scatter shader to created domain, with attribute node with density parameter as density of the shader, Simulate several frames, F12 for render.

**System Information** Lenovo Y580 Intel Core i7-3630QM CPU, 15,6 GiB RAM, Nvidia GeForce GTX 660M (GK107M), Linux Mint 17 64-bit **Blender Version** Broken: Blender 2.71 from buildbot (Hash 4299b00) (and several earlier versions) Worked: Blender 2.71 stable (Hash: 9337574) **Short description of error** Cycles is not rendering direct light with volumetrics, only indirect. **Exact steps for others to reproduce the error** Just starting with the default cube, add to it Object/quick effects/quick smoke, Add a volume scatter shader to created domain, with attribute node with density parameter as density of the shader, Simulate several frames, F12 for render.

Piotr Rogowski commented

2014-07-08 00:42:01 +02:00

Changed status to: 'Open'

Piotr Rogowski commented

2014-07-08 00:42:01 +02:00

Added subscriber: @Rogo

Piotr Rogowski commented

2014-07-08 01:01:17 +02:00

Sorry for that, Didnt know how to edit previous posts. Adding some files according to this bug.
Thank You!

untitled2.blend

Sorry for that, Didnt know how to edit previous posts. Adding some files according to this bug. Thank You! ![wrong.jpg](https://archive.blender.org/developer/F97034/wrong.jpg) ![correct.jpg](https://archive.blender.org/developer/F97035/correct.jpg) [untitled2.blend](https://archive.blender.org/developer/F97038/untitled2.blend)

Adam Friesen commented

2014-07-08 01:26:32 +02:00

Added subscriber: @Ace_Dragon

Adam Friesen commented

2014-07-08 01:26:32 +02:00

You might want to simplify this a little.

Instead of using a smoke object, just add a volumetric material to the cube so verify as to whether or not the issue might be specific to smoke rendering.

Also, if the lamp size is small, you might have trouble getting any sort of lighting on it even if using MIS, though regressions in terms of direct lighting abilities are always possible.

You might want to simplify this a little. Instead of using a smoke object, just add a volumetric material to the cube so verify as to whether or not the issue might be specific to smoke rendering. Also, if the lamp size is small, you might have trouble getting any sort of lighting on it even if using MIS, though regressions in terms of direct lighting abilities are always possible.

Piotr Rogowski commented

2014-07-08 01:44:50 +02:00

Thank you ace_dragon.
Yes, simplified scene reproduces same bug. Just connect a volume scatter shader to default cube (default scene), removing diffuse one. No direct light. Lamp size makes no difference.
Blender 2.71 render is all fine, later versions are not.

Thank you ace_dragon. Yes, simplified scene reproduces same bug. Just connect a volume scatter shader to default cube (default scene), removing diffuse one. No direct light. Lamp size makes no difference. Blender 2.71 render is all fine, later versions are not.

Piotr Rogowski commented

2014-07-08 01:49:12 +02:00

"No direct light" I mean "no direct light" noticeable still in render.
Sorry for flooding.

"No direct light" I mean "no direct light" noticeable still in render. Sorry for flooding.

Thomas Dinges commented

2014-07-08 02:18:13 +02:00

Changed status from 'Open' to: 'Archived'

Thomas Dinges closed this issue

2014-07-08 02:18:13 +02:00

Thomas Dinges self-assigned this 2014-07-08 02:18:13 +02:00

Thomas Dinges commented

2014-07-08 02:18:13 +02:00

Sun Lamps are not supported, as they are infinitely far away.
In the post 2.71 builds, Volume Bounces default to 0, set it to 1, then it should look like the 2.71 release.

1) Sun Lamps are not supported, as they are infinitely far away. 2) In the post 2.71 builds, Volume Bounces default to 0, set it to 1, then it should look like the 2.71 release.

Piotr Rogowski commented

2014-07-08 02:35:36 +02:00

Added subscriber: @ThomasDinges

Piotr Rogowski commented

2014-07-08 02:35:36 +02:00

@ThomasDinges This is bug due to any type of light in this case. I dont use sun lamps. World has no volumetrics. Please download my .blend file and test it. Volume Bounces settings make no differences.

Thomas Dinges commented

2014-07-08 02:43:41 +02:00

I downloaded untitled2.blend and there is a Sun Lamp in it. Switch to Point Lamp, increase strength it works fine!

Piotr Rogowski commented

2014-07-08 02:56:52 +02:00

Ok. I changed light to point and increased its strenhgt. Its working. Still I dont understand why sun does not work with volumes like such domain. I understand why it doesnt work with world volume (pretty reasonable -light at infinite distance and volumetric world) but why doesnt it work here? Volume domain has its thickness, and it should be considered in all calculations. Why is the sunlight in this case???

BTW @ThomasDinges, You are doing such a great job on Cycles!

Ok. I changed light to point and increased its strenhgt. Its working. Still I dont understand why sun does not work with volumes like such domain. I understand why it doesnt work with world volume (pretty reasonable -light at infinite distance and volumetric world) but why doesnt it work here? Volume domain has its thickness, and it should be considered in all calculations. Why is the sunlight in this case??? BTW @ThomasDinges, You are doing such a great job on Cycles!

Adam Friesen commented

2014-07-08 03:47:22 +02:00

You can see for yourself if you 'build' the sun into the environmental light and make it a really small source.

Cycles is a unidirectional pathtracer and that combined with a volume means it will be very hard to illuminate the surface with a source that small.

It's kind of unfortunate really because it means we still have to use stacked cards, the motion blur workaround, or the old internal engine if we want real volumetric cloud and smoke effects in outdoor scenes without tricky compositing tricks, and I'm not sure if there's any papers covering the topic of successfully lighting a cloud from a distant source without a sort of shading cache.

You can see for yourself if you 'build' the sun into the environmental light and make it a really small source. Cycles is a unidirectional pathtracer and that combined with a volume means it will be very hard to illuminate the surface with a source that small. It's kind of unfortunate really because it means we still have to use stacked cards, the motion blur workaround, or the old internal engine if we want real volumetric cloud and smoke effects in outdoor scenes without tricky compositing tricks, and I'm not sure if there's any papers covering the topic of successfully lighting a cloud from a distant source without a sort of shading cache.

Thomas Dinges commented

2014-07-10 21:09:53 +02:00

Changed status from 'Archived' to: 'Open'

Thomas Dinges reopened this issue

2014-07-10 21:09:53 +02:00

Thomas Dinges commented

2014-07-10 21:09:53 +02:00

Actually this is a bug, and was introduced after the 2.71 release, working on a fix atm: D639

Actually this is a bug, and was introduced after the 2.71 release, working on a fix atm: [D639](https://archive.blender.org/developer/D639)

Thomas Dinges commented

2014-07-13 12:15:37 +02:00

Changed status from 'Open' to: 'Resolved'