Sculpt Mode performance drop with Overlays #56466

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Julien Kaspar · 2018-08-20T17:29:31+02:00

Julien Kaspar commented

2018-08-20 17:29:31 +02:00

Blender Version
Broken: d2e70455cf

Short description of error
When disabling Overlays in Sculpt mode the overlay color disappears as well and the performance increases drastically. None of the individual overlay settings seem to cause the performance drop so it might be connected to the overlay color or something else.

**Blender Version** Broken: d2e70455cf4 **Short description of error** When disabling Overlays in Sculpt mode the overlay color disappears as well and the performance increases drastically. None of the individual overlay settings seem to cause the performance drop so it might be connected to the overlay color or something else.

Julien Kaspar commented

2018-08-20 17:29:31 +02:00

Added subscriber: @JulienKaspar

Bastien Montagne commented

2018-08-21 17:12:45 +02:00

Added subscribers: @fclem, @mont29

Clément Foucault was assigned by Bastien Montagne

2018-08-21 17:12:45 +02:00

Bastien Montagne commented

2018-08-21 17:12:45 +02:00

Not sure that is a bug, I guess the whole overlay system is doomed to have some impact over performances… But @fclem shall know more. :)

Clément Foucault commented

2018-08-22 15:35:13 +02:00

Changed status from 'Open' to: 'Archived'

Clément Foucault closed this issue

2018-08-22 15:35:13 +02:00

Clément Foucault commented

2018-08-22 15:35:13 +02:00

Well it's because the sculpt mode overlay is considered as an overlay (huh). So it draws the mesh twice. There is not much we can do because this is by design.

Julien Kaspar commented

2018-08-23 14:26:06 +02:00

@fclem But this is still going to be resolved at some point, preferably before the beta? This seems like a big flaw to me in terms of performance. If the design dictates that the mesh is always going to be drawn twice then it should be changed/adjusted to fix the issue, right?

Clément Foucault commented

2018-08-23 14:54:02 +02:00

Added subscribers: @MikeErwin, @dfelinto, @brecht

Clément Foucault commented

2018-08-23 14:54:02 +02:00

This was a concern I had all the way back when we designed this. But @dfelinto and @MikeErwin told me to not worry about this.

In another hand it does allow us to have decoupling of overlays representation and the underlying render so that you have the same overlay result in eevee and solid mode. Mixing the overlay with the actual shading step would make everything way more complicated.
Also the mesh is rendered as many times there is overlays plus 1. So if you are in sculpt mode + face orientation enabled + wireframe that makes 4 render. We could try to batch face orientation + wireframe together but that's increasing complexity. Batching all overlays together is also a dead end (IMO).

So if someone has an Idea about how to solve this issue I would like to hear it.

Tagging @brecht if he has an opinion.

That said, @JulienKaspar how much of a difference does it makes? is it twice as slow?

This was a concern I had all the way back when we designed this. But @dfelinto and @MikeErwin told me to not worry about this. In another hand it does allow us to have decoupling of overlays representation and the underlying render so that you have the same overlay result in eevee and solid mode. Mixing the overlay with the actual shading step would make everything way more complicated. Also the mesh is rendered as many times there is overlays plus 1. So if you are in sculpt mode + face orientation enabled + wireframe that makes 4 render. We could try to batch face orientation + wireframe together but that's increasing complexity. Batching all overlays together is also a dead end (IMO). So if someone has an Idea about how to solve this issue I would like to hear it. Tagging @brecht if he has an opinion. That said, @JulienKaspar how much of a difference does it makes? is it twice as slow?

Brecht Van Lommel commented

2018-08-23 15:14:30 +02:00

It's not clear to me what this sculpt overlay is doing. I see 3 things:

Show Diffuse Color: this option seems pointless as workbench/eevee can already do it, this is a legacy thing from when sculpt mode did not support drawing materials. Let's remove it?
Show Mask: this is needed, but we should be able to avoid drawing it if there is no masking used.
Darkening of the mesh even when the above two options are disabled, seems the color defaults to 0.8. Let's remove this behavior as well.

So perhaps it's acceptable if masking, face orientation and wireframe cause some slowdown. Maybe masking could be put into workbench shaders if performance matters a lot. But in the simple cases we can avoid drawing the mesh twice?

It's not clear to me what this sculpt overlay is doing. I see 3 things: * Show Diffuse Color: this option seems pointless as workbench/eevee can already do it, this is a legacy thing from when sculpt mode did not support drawing materials. Let's remove it? * Show Mask: this is needed, but we should be able to avoid drawing it if there is no masking used. * Darkening of the mesh even when the above two options are disabled, seems the color defaults to 0.8. Let's remove this behavior as well. So perhaps it's acceptable if masking, face orientation and wireframe cause some slowdown. Maybe masking could be put into workbench shaders if performance matters a lot. But in the simple cases we can avoid drawing the mesh twice?

Brecht Van Lommel commented

2018-08-23 15:44:48 +02:00

Changed status from 'Archived' to: 'Open'

Brecht Van Lommel reopened this issue

2018-08-23 15:44:48 +02:00

Dalai Felinto commented

2018-08-23 15:49:42 +02:00

The idea of having a mode owning the data representation is to make it faster, not slower. For example it allows the sculpt mode to draw straight from BVHs, mesh edit mode from BMesh, ... But if you have an overlay that needs to be updated at every edit there is so much we can do.

Having a dedicated engine for sculpting also allows (in the future) to support mesh preview of to be sculpted mesh and other fancy options.

Anyways, I agree with brecht's suggestions.

The idea of having a mode owning the data representation is to make it faster, not slower. For example it allows the sculpt mode to draw straight from BVHs, mesh edit mode from BMesh, ... But if you have an overlay that needs to be updated at every edit there is so much we can do. Having a dedicated engine for sculpting also allows (in the future) to support mesh preview of to be sculpted mesh and other fancy options. Anyways, I agree with brecht's suggestions.

Julien Kaspar commented

2018-08-23 17:28:59 +02:00

@fclem I think it takes double the performance with overlays on but all additional overlay options disabled. With wireframes, etc it gets drastically worse.

I also agree with Brecht. When using the overlays like wireframe & face orientation the slowdown is alright and to be expected but I am all for removing the extra color differences etc.

@fclem I think it takes double the performance with overlays on but all additional overlay options disabled. With wireframes, etc it gets drastically worse. I also agree with Brecht. When using the overlays like wireframe & face orientation the slowdown is alright and to be expected but I am all for removing the extra color differences etc.

blender-admin commented

2018-08-24 16:46:42 +02:00

This issue was referenced by 0ba3a1a686

This issue was referenced by 0ba3a1a6863a4b5960933df7d5a12d158da5d0d0

Clément Foucault commented

2018-08-24 16:47:05 +02:00

Changed status from 'Open' to: 'Resolved'

Clément Foucault closed this issue

2018-08-24 16:47:05 +02:00

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Sculpt Mode performance drop with Overlays #56466