Smoke Shadow glitches in Cycles (workaround only with Fluid "Empty Space" option) #66791

New Issue

Joao Morgado · 2019-07-12T18:38:08+02:00

Joao Morgado commented

2019-07-12 18:38:08 +02:00

System Information
Operating system: Darwin-17.7.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon HD - FirePro D700 OpenGL Engine ATI Technologies Inc. 4.1 ATI-1.68.21

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-11 13:50, hash: 06312c6d2d
Worked: 2.79

Short description of error
Weird artifacts and boxes appear in the shadows of smoke simulations

Exact steps for others to reproduce the error
I've seen this happening in different simulations with different results. Sometimes it is a big square in the shadows like in the image attached. Sometimes it's just little squares.

Generally speaking the workflow I'm following when I see these errors is the following:

Set the scene to cycles
Create ground plane
Create Sun Light
Create smoke domain
Create smoke emitter with particles
Set smoke flow to emit fire and smoke from particles
Caches simulation
Render with Cycles
Glitches appear in the shadows of the smoke

Attached is a blend file and the render result with glitches

VolumetricsTest.blend

**System Information** Operating system: Darwin-17.7.0-x86_64-i386-64bit 64 Bits Graphics card: AMD Radeon HD - FirePro [D700](https://archive.blender.org/developer/D700) OpenGL Engine ATI Technologies Inc. 4.1 ATI-1.68.21 **Blender Version** Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-11 13:50, hash: `06312c6d2d` Worked: 2.79 **Short description of error** Weird artifacts and boxes appear in the shadows of smoke simulations **Exact steps for others to reproduce the error** I've seen this happening in different simulations with different results. Sometimes it is a big square in the shadows like in the image attached. Sometimes it's just little squares. Generally speaking the workflow I'm following when I see these errors is the following: Set the scene to cycles Create ground plane Create Sun Light Create smoke domain Create smoke emitter with particles Set smoke flow to emit fire and smoke from particles Caches simulation Render with Cycles Glitches appear in the shadows of the smoke Attached is a blend file and the render result with glitches [VolumetricsTest.blend](https://archive.blender.org/developer/F7603474/VolumetricsTest.blend) ![SmokeShadowsError.png](https://archive.blender.org/developer/F7603473/SmokeShadowsError.png)

Joao Morgado commented

2019-07-12 18:38:08 +02:00

Added subscriber: @MrJoMo

blender-admin commented

2019-07-12 18:38:08 +02:00

#79019 was marked as duplicate of this issue

Joao Morgado commented

2019-07-13 06:05:54 +02:00

Here's another example. This time in a Windows 10 machine with an 1050ti card and up to date drivers.
You can see the small dark areas on the floor are shadow glitches.

SmokeShadowError2.blend

Here's another example. This time in a Windows 10 machine with an 1050ti card and up to date drivers. You can see the small dark areas on the floor are shadow glitches. [SmokeShadowError2.blend](https://archive.blender.org/developer/F7604717/SmokeShadowError2.blend) ![SmokeError2.PNG](https://archive.blender.org/developer/F7604716/SmokeError2.PNG)

Sebastian Parborg commented

2019-07-15 12:36:32 +02:00

Added subscriber: @ZedDB

Brecht Van Lommel was assigned by Sebastian Parborg

2019-07-15 12:36:32 +02:00

Sebastian Parborg commented

2019-07-15 12:36:32 +02:00

Might be related to #65793

CRAZ commented

2019-08-16 16:24:37 +02:00

Added subscriber: @zrp

CRAZ commented

2019-08-16 16:24:37 +02:00

It happens to my 980M Nvidia card as well. Upto-date Drivers, and It happens in GPU and CPU mode in cycles.

As you can see, i have moved the house to the left in the second picture. The shadows are glitchy.

If anything, Let me know! thanks!

It happens to my 980M Nvidia card as well. Upto-date Drivers, and It happens in GPU and CPU mode in cycles. ![Capture 1.PNG](https://archive.blender.org/developer/F7667391/Capture_1.PNG) ![Capture 2.PNG](https://archive.blender.org/developer/F7667390/Capture_2.PNG) As you can see, i have moved the house to the left in the second picture. The shadows are glitchy. If anything, Let me know! thanks!

Andrew Price commented

2019-10-25 03:20:43 +02:00

Added subscriber: @AndrewPrice

Andrew Price commented

2019-10-25 03:20:43 +02:00

I've discovered this only appears when High-Resolution is checked in Smoke Domain Settings. And it's more noticeable with more divisions (level 2 onwards).

I'm attaching a .blend for testing. Unchecked it works fine, checked and there's severe artifacts.
test_shadow glitch.blend

I've discovered this only appears when High-Resolution is checked in Smoke Domain Settings. And it's more noticeable with more divisions (level 2 onwards). ![blender_2019-10-25_10-54-34.png](https://archive.blender.org/developer/F7855377/blender_2019-10-25_10-54-34.png) I'm attaching a .blend for testing. Unchecked it works fine, checked and there's severe artifacts. [test_shadow glitch.blend](https://archive.blender.org/developer/F7855383/test_shadow_glitch.blend)

Kenzie commented

2019-10-25 21:14:23 +02:00

Added subscriber: @KenzieMac130

Stefan Werner commented

2019-10-29 23:27:14 +01:00

Added subscriber: @Stefan_Werner

Lord Odin commented

2019-10-30 20:36:17 +01:00

Added subscriber: @derekbarker

Lord Odin commented

2019-10-30 20:36:17 +01:00

I assume its because of the "Empty Space" option under
smoke > settings

Set this number to 0 to fix it

It generates a bounding box around the volume so it renders faster but shadows dont like when many transparent layers are on top of each other, Upping your transparent bounces might fix it as well

I assume its because of the "Empty Space" option under smoke > settings Set this number to 0 to fix it It generates a bounding box around the volume so it renders faster but shadows dont like when many transparent layers are on top of each other, Upping your transparent bounces might fix it as well ![blender_wobv0Zn0af.jpg](https://archive.blender.org/developer/F7873366/blender_wobv0Zn0af.jpg) ![blender_QvtYILXgji.jpg](https://archive.blender.org/developer/F7873365/blender_QvtYILXgji.jpg)

Joao Morgado commented

2019-10-31 03:10:42 +01:00

The empty space parameter actually made it worse when turned to 0. That said, playing a little more with it I found that my ground, was overlapping the edge of the domain, moving it slightly fixed the problem in this scene. I'll need to do more tests to see if that is always the case, or if it just happened for this specific scene.

Lord Odin commented

2019-10-31 03:48:54 +01:00

Did you restart the render completely after changing the parameter? because it wont update automatically, Id like to see a picture of it being worse it might help diagnose the problem

Joao Morgado commented

2019-10-31 04:14:24 +01:00

I did restart the render every time. Attached are render images of both before and after adjusting the empty space parameter and also one of the fix I found, moving the ground plane slightly (0.01)

Before

After

Moving the ground plane

I did restart the render every time. Attached are render images of both before and after adjusting the empty space parameter and also one of the fix I found, moving the ground plane slightly (0.01) Before ![Before.png](https://archive.blender.org/developer/F7874905/Before.png) After ![After.png](https://archive.blender.org/developer/F7874904/After.png) Moving the ground plane ![MovingGroundPlane.png](https://archive.blender.org/developer/F7874906/MovingGroundPlane.png)

Lord Odin commented

2019-10-31 06:02:44 +01:00

I'm talking about the dark black squares in particular, That render seems to be some sort of zfighting

Joao Morgado commented

2019-10-31 12:50:04 +01:00

I hear you. But this was the exact glitch I created this bug report from. Those images are created from the same file I posted when I created the bug report back in July.
Maybe the dark black squares are a different issue. I’ll try later today with the other file I posted.

I hear you. But this was the exact glitch I created this bug report from. Those images are created from the same file I posted when I created the bug report back in July. Maybe the dark black squares are a different issue. I’ll try later today with the other file I posted.

Joao Morgado commented

2019-11-02 21:48:38 +01:00

Derek. It appears you are right. I tried it with my second test file, that had the dark small squares, and turning that value to 0 solved the problem.

Thanks for your help

Derek. It appears you are right. I tried it with my second test file, that had the dark small squares, and turning that value to 0 solved the problem. Thanks for your help

Brecht Van Lommel was unassigned by Dalai Felinto

2019-12-23 16:33:49 +01:00

Dalai Felinto commented

2019-12-23 16:33:49 +01:00

Added subscriber: @brecht

Lord Odin commented

2020-03-01 09:18:26 +01:00

Seems the "empty space" feature doesn't exist anymore since manta flow implementation? If that is the case majority of smoke sims will be pretty broken in cycles renders

Andrew Price commented

2020-03-09 03:44:23 +01:00

Just chiming in to confirm that this is still very much a bug in Blender 2.82 using Mantaflow. Seems to appear in every single smoke animation.
shadow glitch.mp4

Important to note:

It happens with or without noise
It's separate to the Z-fighting issue described in comments above.

Attached blend: shadow glitch demo.blend

Just chiming in to confirm that this is still very much a bug in Blender 2.82 using Mantaflow. Seems to appear in every single smoke animation. [shadow glitch.mp4](https://archive.blender.org/developer/F8396349/shadow_glitch.mp4) Important to note: - It happens with or without noise - It's separate to the Z-fighting issue described in comments above. Attached blend: [shadow glitch demo.blend](https://archive.blender.org/developer/F8396351/shadow_glitch_demo.blend)

Lord Odin commented

2020-03-09 04:36:24 +01:00

In #66791#887239, @AndrewPrice wrote:
Just chiming in to confirm that this is still very much a bug in Blender 2.82 using Mantaflow. Seems to appear in every single smoke animation.
shadow glitch.mp4

Important to note:

It happens with or without noise

It's separate to the Z-fighting issue described in comments above.

Attached blend: shadow glitch demo.blend

Cycles still makes an adaptive volume around the smoke but now you cant change the threshold which honestly makes a lot of renders not usable. :/ Your render appears to be shadows if you turn transparent bounces up to lets say 20 and minimum to 20 as well it may fix it

> In #66791#887239, @AndrewPrice wrote: > Just chiming in to confirm that this is still very much a bug in Blender 2.82 using Mantaflow. Seems to appear in every single smoke animation. > [shadow glitch.mp4](https://archive.blender.org/developer/F8396349/shadow_glitch.mp4) > > Important to note: > - It happens with or without noise > - It's separate to the Z-fighting issue described in comments above. > > Attached blend: [shadow glitch demo.blend](https://archive.blender.org/developer/F8396351/shadow_glitch_demo.blend) Cycles still makes an adaptive volume around the smoke but now you cant change the threshold which honestly makes a lot of renders not usable. :/ Your render appears to be shadows if you turn transparent bounces up to lets say 20 and minimum to 20 as well it may fix it

Maxim Ponomarov commented

2020-03-13 00:18:00 +01:00

Added subscriber: @ponomarovmax

Gottfried Hofmann commented

2020-03-16 16:27:16 +01:00

Added subscribers: @sebbas, @GottfriedHofmann

Gottfried Hofmann commented

2020-03-16 16:27:16 +01:00

I can confirm that increasing the transparent bounces fixes the glitches and that the OPs first problem was indeed Z-fighting.
The empty space feature might be something that needs to be exposed on the Mantaflow side? Assigned to @sebbas for now.

I can confirm that increasing the transparent bounces fixes the glitches and that the OPs first problem was indeed Z-fighting. The empty space feature might be something that needs to be exposed on the Mantaflow side? Assigned to @sebbas for now.

Sebastián Barschkis was assigned by Gottfried Hofmann

2020-03-16 16:27:31 +01:00

Sebastián Barschkis was unassigned by Brecht Van Lommel

2020-03-16 16:30:13 +01:00

Brecht Van Lommel commented

2020-03-16 16:30:13 +01:00

Decisions about who works on what we make ourselves.

Sebastián Barschkis self-assigned this 2020-03-16 17:23:27 +01:00

Sebastián Barschkis commented

2020-03-16 17:23:27 +01:00

This was actually my idea - I'm fine if Gottfried assigns me to the fluids bugs. Helps me keep track of them. Sorry for the confusion.

Sebastián Barschkis removed their assignment 2020-03-17 12:05:06 +01:00

Sebastián Barschkis commented

2020-03-17 12:05:06 +01:00

It's now possible to set the "Empty Space" from the UI again. Note that the value will only affect rendering. See 20d7c04305
So the issue can be circumvented with this value again. I wouldn't say this is a bug though, more a "known issue".

It's now possible to set the "Empty Space" from the UI again. Note that the value will only affect rendering. See 20d7c04305a3 So the issue can be circumvented with this value again. I wouldn't say this is a bug though, more a "known issue".

Sebastián Barschkis changed title from ~~Smoke Shadow glitches in Cycles~~ to Smoke Shadow glitches in Cycles (workaround only with Fluid "Empty Space" option)

2020-03-22 20:22:59 +01:00

mantissa commented

2020-04-22 12:05:16 +02:00

Added subscriber: @Mantissa