From 6af4af8608cf023c4c073f9866f979e3a83e97c0 Mon Sep 17 00:00:00 2001
From: atlas dostal <rodol@rivalrebels.com>
Date: Mon, 16 Jan 2023 14:22:10 -0800
Subject: [PATCH 1/2] Pass precomputed NdotV

---
 crates/bevy_pbr/src/render/pbr_ambient.wgsl   | 13 ++++++-------
 crates/bevy_pbr/src/render/pbr_functions.wgsl |  3 +--
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/crates/bevy_pbr/src/render/pbr_ambient.wgsl b/crates/bevy_pbr/src/render/pbr_ambient.wgsl
index cb8ff6d4fbc9e..5f336f8771652 100644
--- a/crates/bevy_pbr/src/render/pbr_ambient.wgsl
+++ b/crates/bevy_pbr/src/render/pbr_ambient.wgsl
@@ -1,16 +1,15 @@
 #define_import_path bevy_pbr::pbr_ambient
 
 fn ambient_light(
-    world_position: vec4<f32>, 
-    world_normal: vec3<f32>, 
-    V: vec3<f32>, 
-    diffuse_color: vec3<f32>, 
-    specular_color: vec3<f32>, 
+    world_position: vec4<f32>,
+    world_normal: vec3<f32>,
+    V: vec3<f32>,
+    NdotV: f32,
+    diffuse_color: vec3<f32>,
+    specular_color: vec3<f32>,
     perceptual_roughness: f32,
     occlusion: f32,
 ) -> vec3<f32> {
-    let NdotV = max(dot(world_normal, V), 0.0001);
-
     let diffuse_ambient = EnvBRDFApprox(diffuse_color, 1.0, NdotV);
     let specular_ambient = EnvBRDFApprox(specular_color, perceptual_roughness, NdotV);
 
diff --git a/crates/bevy_pbr/src/render/pbr_functions.wgsl b/crates/bevy_pbr/src/render/pbr_functions.wgsl
index 8bfa3a5a93aa9..4e3bf3d8ea9e4 100644
--- a/crates/bevy_pbr/src/render/pbr_functions.wgsl
+++ b/crates/bevy_pbr/src/render/pbr_functions.wgsl
@@ -231,7 +231,7 @@ fn pbr(
         light_accum = light_accum + light_contrib * shadow;
     }
 
-    let ambient_contrib = ambient_light(in.world_position, in.N, in.V, diffuse_color, F0, perceptual_roughness, occlusion);
+    let ambient_contrib = ambient_light(in.world_position, in.N, in.V, NdotV, diffuse_color, F0, perceptual_roughness, occlusion);
 
     output_color = vec4<f32>(
         light_accum + ambient_contrib + emissive.rgb * output_color.a,
@@ -264,4 +264,3 @@ fn dither(color: vec4<f32>, pos: vec2<f32>) -> vec4<f32> {
     return vec4<f32>(color.rgb + screen_space_dither(pos.xy), color.a);
 }
 #endif
-

From fa88d767ad7a1fb843729d423b3ccec951acce2d Mon Sep 17 00:00:00 2001
From: atlas dostal <rodol@rivalrebels.com>
Date: Mon, 16 Jan 2023 14:24:22 -0800
Subject: [PATCH 2/2] Document NdotV vs N and V

---
 crates/bevy_pbr/src/render/pbr_ambient.wgsl | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crates/bevy_pbr/src/render/pbr_ambient.wgsl b/crates/bevy_pbr/src/render/pbr_ambient.wgsl
index 5f336f8771652..8ef380ac5a2f1 100644
--- a/crates/bevy_pbr/src/render/pbr_ambient.wgsl
+++ b/crates/bevy_pbr/src/render/pbr_ambient.wgsl
@@ -1,5 +1,7 @@
 #define_import_path bevy_pbr::pbr_ambient
 
+// A precomputed `NdotV` is provided because it is computed regardless,
+// but `world_normal` and the view vector `V` are provided separately for more advanced uses.
 fn ambient_light(
     world_position: vec4<f32>,
     world_normal: vec3<f32>,