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Clamp SpotLight.outer_angle to pi/2-epsilon at extraction time #24734

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Clamp SpotLight.outer_angle to pi/2-epsilon at extraction time #24734

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4176a0f
fix: clamp SpotLight.outer_angle to pi/2 - epsilon at extraction time
dylansechet Jun 23, 2026
5af1b96
doc: update SpotLight doc to explicitely forbid outer_angle=pi/2
dylansechet Jun 23, 2026
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4 changes: 1 addition & 3 deletions crates/bevy_light/src/spot_light.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -124,9 +124,7 @@ pub struct SpotLight {

/// Angle defining the distance from the spot light direction to the outer limit
/// of the light's cone of effect.
/// `outer_angle` should be < `PI / 2.0`.
/// `PI / 2.0` defines a hemispherical spot light, but shadows become very blocky as the angle

@kfc35 kfc35 Jun 24, 2026

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Is this not true anymore? Just wondering the reason for the removal

@dylansechet dylansechet Jun 24, 2026 •
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I feel like publicly documenting the behavior of an unsupported value sends a confusing message. To me this read as "pi/2 is possible, with the only downside that you might get weird shadows".

/// approaches this limit.
/// `outer_angle` must be < `PI / 2.0`.
pub outer_angle: f32,

/// Angle defining the distance from the spot light direction to the inner limit
Expand Down
21 changes: 18 additions & 3 deletions crates/bevy_pbr/src/render/light.rs
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Expand Up @@ -27,6 +27,7 @@ use bevy_light::{
Cascades, DirectionalLight, DirectionalLightShadowMap, GlobalAmbientLight, PointLight,
PointLightShadowMap, RectLight, ShadowFilteringMethod, SpotLight, VolumetricLight,
};
use bevy_log::warn_once;
use bevy_material::{
key::{ErasedMaterialPipelineKey, ErasedMeshPipelineKey},
MaterialProperties,
Expand Down Expand Up @@ -638,8 +639,22 @@ pub fn extract_lights(
));
}

let texel_size =
2.0 * ops::tan(spot_light.outer_angle) / directional_light_shadow_map.size as f32;
// `outer_angle` must be <π/2.
let (inner_angle, outer_angle) = {
let mut outer_angle = spot_light.outer_angle;
if outer_angle >= core::f32::consts::FRAC_PI_2 {
warn_once!(
"A `SpotLight` has `outer_angle` {} >= π/2 (~1.57079), clamping it to just below π/2. \
Spot lights require `outer_angle < π/2`",
outer_angle
);
outer_angle = core::f32::consts::FRAC_PI_2 - 1e-4;

@dylansechet dylansechet Jun 23, 2026

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The 1e-4 is completely arbitrary

}
// Keep inner_angle <= outer_angle after clamping.
(spot_light.inner_angle.min(outer_angle), outer_angle)
};

let texel_size = 2.0 * ops::tan(outer_angle) / directional_light_shadow_map.size as f32;

let mut entity_commands = commands.entity(render_entity);
let extracted_spot_light = ExtractedPointLight {
Expand All @@ -662,7 +677,7 @@ pub fn extract_lights(
* texel_size
* core::f32::consts::SQRT_2,
shadow_map_near_z: spot_light.shadow_map_near_z,
spot_light_angles: Some((spot_light.inner_angle, spot_light.outer_angle)),
spot_light_angles: Some((inner_angle, outer_angle)),
volumetric: volumetric_light.is_some(),
affects_lightmapped_mesh_diffuse: spot_light.affects_lightmapped_mesh_diffuse,
#[cfg(feature = "experimental_pbr_pcss")]
Expand Down
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