Maniphest T56939

Heavy instancing cause Cycles hardware utilization drop to a fraction because of "Updating Camera Volume"
Closed, ResolvedKNOWN ISSUE
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Assigned To
Thomas Dinges (dingto)
Authored By
Ludvik Koutny (rawalanche)
Sep 27 2018, 5:43 PM
Tags
  • BF Blender
  • Cycles
  • Render & Cycles
Subscribers
Bastien Montagne (mont29)
Brecht Van Lommel (brecht)
Ludvik Koutny (rawalanche)
Milan Jaros (jar091)
Richard Antalik (ISS)
Thomas Dinges (dingto)

Description

System Information
Windows 10, GTX1080Ti

Blender Version
Broken: 2.79 latest master
Worked: probably never

Short description of error
Cycles performance and hardware utilization degrades severely with heavy instancing (I have tried to utilize particle system to generate forest covered mountains). The culprit of the poor utilization seems to be a process described as "Updating Camera Volume" on which most of the time in rendered viewport mode is spent, resulting in usages between 20-30% in both CPU and GPU mode.

It happens only in "rendered" viewport mode, not in the final frame render mode. In final frame render mode, "Updating Camera Volume" is not part of process, hardware utilization seems correct and so does the performance.

Exact steps for others to reproduce the error
1, Open the attached blend file:

TerrainFun_V01.zip156 KBDownload

2, Switch the viewport mode to rendered
3, Observe poor performance, poor interactivity and low hardware utilization.
4, Switch viewport mode back to shaded and launch final frame rendering (F12 key)
5, Observe proper performance and full hardware utilization

Result: Cycles' performance and hardware utilization reduces drastically with growing amount of instances in rendered viewport mode

Expected; Cycles' performance and hardware utilization is consistently good between viewport and final frame mode regardless of instance count.

Revisions and Commits

rC Cycles
D8261rC43678495b915 Optimize camera inside volume tests
rB Blender
D8261rBad45b8d6a439 Cycles: optimize camera inside volume tests

Related Objects

Mentioned Here
rBad45b8d6a439: Cycles: optimize camera inside volume tests

Event Timeline

Ludvik Koutny (rawalanche) created this task.Sep 27 2018, 5:43 PM
Bastien Montagne (mont29) assigned this task to Brecht Van Lommel (brecht).Sep 30 2018, 6:51 PM
Bastien Montagne (mont29) lowered the priority of this task from 90 to Normal.
Bastien Montagne (mont29) added subscribers: Brecht Van Lommel (brecht), Bastien Montagne (mont29).

That does not really sounds like a bug to me, but will let @Brecht Van Lommel (brecht) decide here.

Ludvik Koutny (rawalanche) added a comment.Oct 1 2018, 8:45 AM
In T56939#538694, @Bastien Montagne (mont29) wrote:

That does not really sounds like a bug to me, but will let @Brecht Van Lommel (brecht) decide here.

I am sure it is, due to four reasons:

1, There is no other path tracer out there that slows down so drastically with growing amount of instances.

2, There is no other path tracer out there where hardware utilization drops to as low as 1/3rd with as little as 1 million instances.

3, The poor performance and utilization happens only in viewport render mode, not in final frame render mode, so cycles is capable of performing well and utilizing hardware fully.

4, The status message says "Updating Camera Volume" which implies there is some inefficient way of calculating global volume boundaries, which is all the more confusing given that the scene does not use any global volume shader at all, so there's no reason to compute it in the first place.

Dalai Felinto (dfelinto) removed Brecht Van Lommel (brecht) as the assignee of this task.Dec 23 2019, 4:35 PM
Dalai Felinto (dfelinto) added a project: Tracker Curfew.
Richard Antalik (ISS) changed the task status from Confirmed to Needs Information from User.Feb 11 2020, 12:32 AM
Richard Antalik (ISS) added a subscriber: Richard Antalik (ISS).

I have re-triaged this report and can not reproduce it.
Rendered mode in viewport used 100% CPU. Perhaps it is slower. but whole UI is slower.

Can you please check if this is still an issue in latest build?
https://builder.blender.org/download/

Ludvik Koutny (rawalanche) added a comment.EditedFeb 11 2020, 9:31 AM
In T56939#869254, @Richard Antalik (ISS) wrote:

I have re-triaged this report and can not reproduce it.
Rendered mode in viewport used 100% CPU. Perhaps it is slower. but whole UI is slower.

Can you please check if this is still an issue in latest build?
https://builder.blender.org/download/

Tested with the latest 2.82 build. The main problem still remains, the performace of Cycles being absolutely horrible with as little as million instances. Even with all the viewport overlays disabled, just simple orbiting in the viewport runs at about one frame every 3 seconds. There's absolutely nothing that should slow down view navigation in a path tracer renderer in such a trivial scene.

Unlike 2.79, utilization is now nearly full, but I bet only fraction of it is actually spent on rendering.

Richard Antalik (ISS) changed the task status from Needs Information from User to Confirmed.Feb 11 2020, 5:23 PM
Richard Antalik (ISS) removed a project: Tracker Curfew.
Richard Antalik (ISS) changed the subtype of this task from "Report" to "Known Issue".
Brecht Van Lommel (brecht) added a project: Render & Cycles.Jun 18 2020, 6:16 PM
Milan Jaros (jar091) added a subscriber: Milan Jaros (jar091).Jul 10 2020, 11:02 AM
Milan Jaros (jar091) added a comment.Jul 10 2020, 1:00 PM

Maybe this could help: D8261

Brecht Van Lommel (brecht) added a commit: rBad45b8d6a439: Cycles: optimize camera inside volume tests.Jul 10 2020, 5:15 PM
Brecht Van Lommel (brecht) added a commit: rC43678495b915: Optimize camera inside volume tests.Sep 1 2020, 1:53 AM
Thomas Dinges (dingto) closed this task as Resolved.Nov 25 2022, 3:06 PM
Thomas Dinges (dingto) claimed this task.
Thomas Dinges (dingto) added a subscriber: Thomas Dinges (dingto).

I guess rBad45b8d6a439 fixed the issue and this should be closed. I cannot see any wrong "Updating Camera Volume" status prints with Blender 3.5. Viewport performance is slow, but that's in solid mode as well. Render utilization with CPU is 100% for both Viewport and F12 render.