Directional light shadows disappear when camera is rotated

[GitGhillie]

Bevy version

0.10.1,
main (f76b3c4)

Relevant system information

• SteamOS 3.4.6
  AdapterInfo { name: "AMD Custom GPU 0405 (RADV VANGOGH)", vendor: 4098, device: 5695, device_type: IntegratedGpu, driver: "radv", driver_info: "Mesa 22.2.5", backend: Vulkan }

What you did

• Spawn two horizontal planes above each other
• Spawn directional light and a camera between the planes
• Rotate camera

See somewhat minimal example here.

What went wrong

Depending on the distance and angle of the camera some shadows partially disappear. As seen here it can quickly ruin a scene.

In the example code I gave only rectangular shadows should be possible but when you spawn in it looks like this:

Move around the camera with the mouse and you will see the shadow change shape.

Additional information

Same issue on my Windows 10 desktop (tested with Bevy 0.10.1) but I'm currently abroad so I cannot check the exact AdapterInfo. It has an AMD Vega 56 gpu and uses the Vulkan backend as well.

[DGriffin91]

I've also noticed this issue.

[GitGhillie]

@DGriffin91 good to know it's not just me. Are you also using Vulkan + AMD card?

[DGriffin91]

I've seen it on both DX12 and Vulkan on Nvidia. I think it's probably an issue with the directional light shadow cascade calculations. Maybe something in:

bevy/crates/bevy_pbr/src/light.rs

Line 513 in ca81d3e

fn calculate_cascade(

[DGriffin91]

Here's a video of the issue:

2023-05-30.21-02-49.mp4

This is with these settings:

CascadeShadowConfigBuilder {
    num_cascades: 4,
    minimum_distance: 0.01,
    maximum_distance: 50.0,
    first_cascade_far_bound: 3.0,
    overlap_proportion: 0.2,
}

This issue also happens in the sponza test scene.

[superdump]

Hmm, I can't seem to reproduce with the example code on an M1 Max in macOS. Could someone make a video of the problem with the example code? Or else make a minimal example that reproduces the problem, plus a video showing the problem you see?

[superdump]

Ok, I tried on AdapterInfo { name: "NVIDIA GeForce RTX 3080 Laptop GPU", vendor: 4318, device: 9372, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "528.02", backend: Vulkan } on Windows 11 and it looked fine. But with WGPU_BACKEND=dx12 I see the issue. The shadow on the plane beneath the camera should be rectangular, but when looking down a bit the corner kind of inverts such that light cuts into the shadow region. Hmm, @danchia and @DGriffin91 were discussing near plane problems on Discord and now I've seen it first hand I'm inclined to agree.

[DGriffin91]

@superdump I made a little test, the included one was a bit disorienting for me: https://github.com/DGriffin91/bevy_csm_test I see the issue on both vulkan and dx12 on a RTX3060. I have the camera spawn near one issue. You can also see it it you go up to one of the upper corners.

[GitGhillie]

cascades.mp4

Looks like the issue occurs near the camera and near the cascade bounds.
Cascade settings for this video:

cascade_shadow_config: CascadeShadowConfigBuilder {
                num_cascades: 3,
                maximum_distance: 20.0,
                overlap_proportion: 0.0,
                ..default()
            }

[GitGhillie]

Discord thread on the issue

[DGriffin91]

This appears to still be an issue in sponza with bevy 0.11
https://github.com/DGriffin91/bevy_sponza_scene

[DGriffin91]

This appears to still be an issue in bistro with bevy 0.11
https://github.com/DGriffin91/bevy_bistro_scene