Expose ssao radius

[GageHowe]

Expose the SSAO sampling radius as a public configuration option on
ScreenSpaceAmbientOcclusion.

Right now Bevy exposes SSAO quality and constant object thickness, but the effect
radius is still hardcoded internally in the SSAO shader. That makes it impossible for
users to tune the size of the occlusion effect from app code.

Solution

Add a radius: f32 field to ScreenSpaceAmbientOcclusion and preserve existing behavior
by defaulting it to the shader’s previous hardcoded value.

To wire that through cleanly, the SSAO render path now uploads a small SSAO settings
uniform containing both radius and constant_object_thickness, and the SSAO shader
reads settings.radius instead of a hardcoded constant.

The SSAO example was also updated to expose the new setting interactively so the
feature is discoverable and easy to validate.

Testing

I tested this by:

• Running cargo check -p bevy_pbr --quiet
• Building and running cargo build --example ssao
• Launching target/debug/examples/ssao and verifying the example starts successfully
• Verifying that the new radius control can be adjusted interactively in the example
  with Left / Right

Parts that could use more testing:

• Visual validation across a wider range of scenes and camera scales
• Broader GPU/platform coverage, since I only tested locally

How reviewers can test this:

1. Run cargo build --example ssao
2. Launch target/debug/examples/ssao
3. Use Left / Right to decrease/increase SSAO radius
4. Confirm that larger values produce broader occlusion while the default matches
   existing behavior

Platform tested:

• Linux (EndeavourOS)

Platforms not tested:

• Windows
• macOS
• Web targets

[Copilot]

Pull request overview

This PR exposes the SSAO sampling radius as a public configuration option on ScreenSpaceAmbientOcclusion, wiring the value through the render pipeline via a new settings uniform and updating the SSAO shader to consume it.

Changes:

• Add radius: f32 to ScreenSpaceAmbientOcclusion with a default matching the previously hardcoded shader value.
• Upload a combined SSAO settings uniform (radius + constant object thickness) and update the SSAO shader to read from it.
• Extend the ssao example to allow interactive radius adjustment and display the current value.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
examples/3d/ssao.rs	Adds Left/Right controls and on-screen text for the new SSAO radius setting.
crates/bevy_pbr/src/ssao/ssao.wgsl	Replaces the hardcoded effect radius with a uniform-driven radius in the SSAO compute shader.
crates/bevy_pbr/src/ssao/mod.rs	Adds the public radius field, defines a default, and uploads a settings uniform buffer to the shader.

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[GageHowe]