Cycles: Blurry Volumetric & Very Long Render Time in 4.0 #115162

New Issue

Cy · 2023-11-20T09:02:58+01:00

Cy commented

2023-11-20 09:02:58 +01:00

System Information
Operating system: macOS-13.6.1-x86_64-i386-64bit 64 Bits
Graphics card: Metal API AMD Radeon RX 6900 XT 1.2

Blender Version
Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: d0dd92834a08
Worked: (newest version of Blender that worked as expected)

Short description of error
Volumetrics are blurry compared to 3.6.5 with exact same settings. And blender 4.0.1 cycles render much slower than 3.6 too. Render time increased from 17.7 seconds in 3.6.5, to 3 minutes in 4.0.1

Exact steps for others to reproduce the error
About the screenshot, Blender 3.6.5 is on the left, and Blender 4.0.1 is on the right.
I've attached a blend file for testing too, just press render and see the difference.

**System Information** Operating system: macOS-13.6.1-x86_64-i386-64bit 64 Bits Graphics card: Metal API AMD Radeon RX 6900 XT 1.2 **Blender Version** Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: `d0dd92834a08` Worked: (newest version of Blender that worked as expected) **Short description of error** Volumetrics are blurry compared to 3.6.5 with exact same settings. And blender 4.0.1 cycles render much slower than 3.6 too. Render time increased from 17.7 seconds in 3.6.5, to 3 minutes in 4.0.1 **Exact steps for others to reproduce the error** About the screenshot, Blender 3.6.5 is on the left, and Blender 4.0.1 is on the right. I've attached a blend file for testing too, just press render and see the difference.

Cloud.blend

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Screenshot 2023-11-20 at 3.29.48 PM.png

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Cy added the

labels 2023-11-20 09:02:59 +01:00

Jesse Yurkovich commented

2023-11-21 03:52:47 +01:00

That the volume looks different (less crisp) is a by-design change between the versions -- notice that the Volume to Mesh modifier is different when loaded in 3.6 vs 4.x (700d168a5c, https://wiki.blender.org/wiki/Reference/Release_Notes/4.0/Geometry_Nodes#General).

As for the difference in render time, I can't really reproduce that locally (Win11 + nvidia). We'll have to see if one of our Mac developers can reproduce the render time issue.

That the volume looks different (less crisp) is a by-design change between the versions -- notice that the Volume to Mesh modifier is different when loaded in 3.6 vs 4.x (700d168a5c7, https://wiki.blender.org/wiki/Reference/Release_Notes/4.0/Geometry_Nodes#General). As for the difference in render time, I can't really reproduce that locally (Win11 + nvidia). We'll have to see if one of our Mac developers can reproduce the render time issue.

Jesse Yurkovich added the

Platform

macOS

label 2023-11-21 03:52:56 +01:00

Alaska commented

2023-11-22 12:51:19 +01:00

I personally can not reproduce a performance slow down on a M1 Pro when comparing Blender 3.6.5 to 4.0.1.

It's highly likely this is another rendering slow down on AMD GPUs on macOS caused by general changes to shaders, similar to #112596.

@brecht or @Michael-Jones, are you willing to take a look at this?

I personally can not reproduce a performance slow down on a M1 Pro when comparing Blender 3.6.5 to 4.0.1. It's highly likely this is another rendering slow down on AMD GPUs on macOS caused by general changes to shaders, similar to #112596. @brecht or @Michael-Jones, are you willing to take a look at this?

Richard Antalik commented

2023-11-23 05:43:23 +01:00

Also can't reproduce on Intel Mac with 5700XT GPU

Alaska commented

2023-11-23 05:53:05 +01:00

Maybe @TheCGCy was waiting for the Metal kernels to compile on 4.0 and included that in the render time, but didn't in the 3.6.5 render? Or maybe they're using Metal-RT on one and not the other, and it may have a performance issue. Or maybe there's a issue specific to the RX 6000 series? Or maybe the user was accidentally using their CPU instead of their GPU in 4.0.

@TheCGCy can you make sure that in 4.0 you have your GPU enabled? And double check that your Metal-RT option matches your setting for 3.6.5.

And when running performance render tests. Try rendering the scene twice and use the second render for timing (The second render is basically guaranteed to not compile any kernels.)

If performance is still bad, then please let us know whether or not you're using Metal-RT.

Maybe @TheCGCy was waiting for the Metal kernels to compile on 4.0 and included that in the render time, but didn't in the 3.6.5 render? Or maybe they're using Metal-RT on one and not the other, and it may have a performance issue. Or maybe there's a issue specific to the RX 6000 series? Or maybe the user was accidentally using their CPU instead of their GPU in 4.0. @TheCGCy can you make sure that in 4.0 you have your GPU enabled? And double check that your Metal-RT option matches your setting for 3.6.5. And when running performance render tests. Try rendering the scene twice and use the second render for timing (The second render is basically guaranteed to not compile any kernels.) If performance is still bad, then please let us know whether or not you're using Metal-RT.

Pratik Borhade added

Status

Needs Information from User

and removed

Status

Needs Triage

labels 2023-11-23 06:56:23 +01:00

Cy commented

2023-11-23 11:35:45 +01:00

Yes, it is set to GPU render only, and the render kernel had finished compiling long ago. I made several renders to test again, it was consistent for about 3 min.
I'm still using Ventura 13.6.1 at the moment. ~~Back when metal-RT was experimental, enabling it crashes Blender, so I never bothered to enable it~~. I can't seem to find it anymore in 3.6 and 4.0, probably incompatible hardware.

Correction: I was wrong, I mistaken HIP-RT with Metal-RT, I never experimented with Metal-RT, sorry bout that.

Yes, it is set to GPU render only, and the render kernel had finished compiling long ago. I made several renders to test again, it was consistent for about 3 min. I'm still using Ventura 13.6.1 at the moment. ~~Back when metal-RT was experimental, enabling it crashes Blender, so I never bothered to enable it~~. I can't seem to find it anymore in 3.6 and 4.0, probably incompatible hardware. ###### Correction: I was wrong, I mistaken HIP-RT with Metal-RT, I never experimented with Metal-RT, sorry bout that.

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Alaska commented

2023-11-23 11:59:09 +01:00

I can't seem to find it anymore in 3.6 and 4.0, probably incompatible hardware.

The MetalRT setting is hidden in Blender 4.0 unless you are on macOS 14.X. I forgot about that before asking you to check.

I'm not 100% sure what's causing the issue then. Maybe updates available in newer macOS versions fix the performance issue? Maybe this is a issue specific to the RX 6000 series? Maybe you have a add-on that's incompatible with Blender 4.0 that's experiencing errors and is causing a slow down?

Since I don't have access to equivalent hardware, I can't test it. Sorry.

On the topic of the add-on thing. Could you try testing without add-ons. It can be done by:

Select from the top of Blender File -> Defaults -> Load Factory Settings
Go to preferences and re-enable your GPU.
Open your test file and render.

If that fixes the performance slow down, then there's something wrong with one of your add-ons, or how Blender is handling it. And if you could, are you able to try disabling add-ons one by one until the issue is fixed and either report the issue to the add-on developer or to us if it's a add-on that comes with Blender.
If it doesn't fix the performance, then we're back to the "I'm not 100% sure what's causing it" situation.

> I can't seem to find it anymore in 3.6 and 4.0, probably incompatible hardware. The MetalRT setting is hidden in Blender 4.0 unless you are on macOS 14.X. I forgot about that before asking you to check. I'm not 100% sure what's causing the issue then. Maybe updates available in newer macOS versions fix the performance issue? Maybe this is a issue specific to the RX 6000 series? Maybe you have a add-on that's incompatible with Blender 4.0 that's experiencing errors and is causing a slow down? Since I don't have access to equivalent hardware, I can't test it. Sorry. --- On the topic of the add-on thing. Could you try testing without add-ons. It can be done by: 1. Select from the top of Blender `File -> Defaults -> Load Factory Settings` 2. Go to preferences and re-enable your GPU. 3. Open your test file and render. If that fixes the performance slow down, then there's something wrong with one of your add-ons, or how Blender is handling it. And if you could, are you able to try disabling add-ons one by one until the issue is fixed and either report the issue to the add-on developer or to us if it's a add-on that comes with Blender. If it doesn't fix the performance, then we're back to the "I'm not 100% sure what's causing it" situation.

Cy commented

2023-11-23 13:41:44 +01:00

Hmm, nope, still the same. I tried to remove all my Blender user preference folders to start anew. Open the Blend file without Load UI and re-enable GPU. Tried GPU Experimental, and I even tested rendering with both CPU and GPU enabled.

And to my surprise, when rendered with CPU only, is about 40 seconds faster than GPU. CPU finishes at 2 min 4 sec.

Hmm, nope, still the same. I tried to remove all my Blender user preference folders to start anew. Open the Blend file without Load UI and re-enable GPU. Tried GPU Experimental, and I even tested rendering with both CPU and GPU enabled. And to my surprise, when rendered with CPU only, is about 40 seconds faster than GPU. CPU finishes at 2 min 4 sec.

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Alaska added

Status

Needs Triage

and removed

Status

Needs Information from User

labels 2023-11-23 23:44:57 +01:00

Alaska commented

2023-11-23 23:47:02 +01:00

I've changed it back to Needs Triage because I don't know what other tests can be done to track down the issue, and I don't have the hardware to do testing myself.

I've changed it back to `Needs Triage` because I don't know what other tests can be done to track down the issue, and I don't have the hardware to do testing myself.

Pratik Borhade commented

2023-12-08 06:35:16 +01:00

Hi, unable to confirm either the render time difference (on Windows though).
Could you verify again in fresh 4.1 build (without importing previous version settings)?: https://builder.blender.org/download/daily/

Hi, unable to confirm either the render time difference (on Windows though). Could you verify again in fresh 4.1 build (without importing previous version settings)?: https://builder.blender.org/download/daily/

Pratik Borhade added

Status

Needs Information from User

and removed

Status

Needs Triage

labels 2023-12-08 06:35:33 +01:00

Cy commented

2023-12-09 02:05:06 +01:00

No, 4.1 Alpha (ref: 2b0448c91d) too, doesn't improve render time. it's a few seconds slower, up from 2:55 to 3:01. It's about the same as 4.0.2.

CPU render time
2:14
2:20

GPU render time
3:01
3:07
3:02

No, 4.1 Alpha (ref: 2b0448c91d7a) too, doesn't improve render time. it's a few seconds slower, up from 2:55 to 3:01. It's about the same as 4.0.2. CPU render time 2:14 2:20 GPU render time 3:01 3:07 3:02

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Iliya Katushenock commented

2023-12-09 11:05:48 +01:00

Not sure if that is related, but here is dependency cycle in example file :

Dependency cycle detected:
  SCScene/PARAMETERS_EVAL() depends on
  SCScene/DRIVER(cycles.preview_denoising_start_sample) via 'Driver -> Driven Property'
  SCScene/PARAMETERS_EVAL() via 'RNA Target -> Driver'
Detected 1 dependency cycles

I can confirm x2 longer render and blurry volume:

3.6.5	4.1

Not sure if that is related, but here is dependency cycle in example file : ``` Dependency cycle detected: SCScene/PARAMETERS_EVAL() depends on SCScene/DRIVER(cycles.preview_denoising_start_sample) via 'Driver -> Driven Property' SCScene/PARAMETERS_EVAL() via 'RNA Target -> Driver' Detected 1 dependency cycles ``` I can confirm x2 longer render and blurry volume: | 3.6.5 | 4.1 | | -- | -- | | ![image](/attachments/dd144dc3-facb-47a7-a881-b11f83d27ac9) | ![image](/attachments/77e6e0b7-00b1-4a40-a8ea-a141a2b6b4f6) |

image.png

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Cy commented

2023-12-10 03:08:52 +01:00

@mod_moder Yeah, that is just a simple driver to make denoiser run at the end of samples, but the Test file wasn't utilizing any denoiser, just to be consistent. That part can be ignored.

Screenshot 2023-12-10 at 10.05.07 AM.png

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