1-frame rendering flashes when changing the scene

[JMS55]

Bevy version

0.16-dev since 5e569af.

What you did

Run cargo run --example anti_aliasing, and toggle back and forth between the different AA methods (give the first few times a few seconds to compile the pipelines).

What went wrong

Switching the AA method causes a 1-frame flash where the mesh doesn't render properly.

[hukasu]

messing with the anti_aliasing example i noticed this, the flash happens when changing out of FXAA, SMAA, and TAA

To \ From	No AA	MSAA	FXAA	SMAA	TAA
No AA		X	O	O	O
MSAA	X		O	O	O
FXAA	X	X		O	O
SMAA	X	X	O		O
TAA	X	X	O	O

[superdump]

Does X mean the flash happens and O means it doesn't?

[hukasu]

@superdump the opposite, X no flash, O flash

[JMS55]

I did a little more debugging.

The issue is specifically with shadows not rendering for 1(?) frame when something with the view changes (not sure exactly what yet).

If I comment out this line, the bug goes away.

bevy/crates/bevy_pbr/src/render/light.rs

Line 1900 in 205ae64

specialized_material_pipeline_cache.retain(|view, _| all_shadow_views.contains(view));

[JMS55]

Even more debugging: it happens for exactly 1 frame, and it's due to this query:

bevy/crates/bevy_pbr/src/render/light.rs

Line 1739 in 205ae64

view_lights: Query<(Entity, &ViewLightEntities), With<ExtractedView>>,

matching 0 entities.

This causes all_shadow_views to be empty, so the pipeline cache gets entirely emptied out.

[JMS55]

Ah ok so it's a system ordering issue.

specialize_shadows::<M>.in_set(RenderSet::PrepareMeshes);
prepare_lights.in_set(RenderSet::ManageViews);

PrepareMeshes runs before ManageViews, but specialize_shadows needs to run after prepare_lights.