Depsgraph deferred evaluation design #82605

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opened 2020-11-11 05:12:56 +01:00 by YimingWu · 8 comments
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For heavy modifiers, evaluation will take a lot of time, while the UI is locked, which affects user experience. Deferred (background) evaluation will allow:

  1. UI to be responsive while calculation is happening in the background.
  2. Showing progress in the UI.
  3. Other interactive stuff (?)

This function will eventually be needed anyway so I set up a task here while I poke around the code to find a doable design.

For heavy modifiers, evaluation will take a lot of time, while the UI is locked, which affects user experience. Deferred (background) evaluation will allow: 1. UI to be responsive while calculation is happening in the background. 2. Showing progress in the UI. 3. Other interactive stuff (?) This function will eventually be needed anyway so I set up a task here while I poke around the code to find a doable design.
YimingWu self-assigned this 2020-11-11 05:12:56 +01:00
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Added subscribers: @ChengduLittleA, @brecht, @Sergey

Added subscribers: @ChengduLittleA, @brecht, @Sergey
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https://wiki.blender.org/wiki/User:Yiming/Deferred_Updates_For_Depsgraph I created this wiki page to put my notes in.

Decoupling scene evaluation from the interface thread is something nice to have eventually, so that Blender never hangs, sliders are always responsive, and maybe even cancelling heavy subdivision level will be possible. But this is something which is to be done on a dependency graph level, not on individual modifiers level, so does not really solve your specific case.

The proposal you are bringing up here does not cover topics like:

  • Thread safety.
  • Integration with scripting, which is crucial for I/O.
  • Data consistency (both for code which interacts with the dependency graph, and for animators which observes result in the viewport).

Those are complicated topics, and I do not think this is something we want to commit for.

To me it seems that something what has a weak design is attempted to be worked around by introducing such deferred evaluation. I think proper solution here is to take a step back, and reconsider design of the project you are working on, so that it fits into current Blender, its product values (mainly, that everything must be designed real-time), its current architectural design.

Decoupling scene evaluation from the interface thread is something nice to have eventually, so that Blender never hangs, sliders are always responsive, and maybe even cancelling heavy subdivision level will be possible. But this is something which is to be done on a dependency graph level, not on individual modifiers level, so does not really solve your specific case. The proposal you are bringing up here does not cover topics like: * Thread safety. * Integration with scripting, which is crucial for I/O. * Data consistency (both for code which interacts with the dependency graph, and for animators which observes result in the viewport). Those are complicated topics, and I do not think this is something we want to commit for. To me it seems that something what has a weak design is attempted to be worked around by introducing such deferred evaluation. I think proper solution here is to take a step back, and reconsider design of the project you are working on, so that it fits into current Blender, its product values (mainly, that everything must be designed real-time), its current architectural design.
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Added subscriber: @lichtwerk

Added subscriber: @lichtwerk
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Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'
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@ChengduLittleA : is this still being considered? If so, please set the status to Confirmed.

@ChengduLittleA : is this still being considered? If so, please set the status to `Confirmed`.
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Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'

Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'
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This is put forward in the context of line art evaluation (which is often slow), although we eventually changed line art into the modifier, it still doesn't change the nature that evaluation would lock the interface. So I consider this topic still valid.

This is put forward in the context of line art evaluation (which is often slow), although we eventually changed line art into the modifier, it still doesn't change the nature that evaluation would lock the interface. So I consider this topic still valid.
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Reference: blender/blender#82605
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