From d3bfccdc4f90aabfa3493b0db0e6fe357a527485 Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Sat, 1 Nov 2025 21:07:26 -0700
Subject: Notes

---
 shaders/cook_torrance.frag | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

(limited to 'shaders/cook_torrance.frag')

diff --git a/shaders/cook_torrance.frag b/shaders/cook_torrance.frag
index c0c666c..f6c6048 100644
--- a/shaders/cook_torrance.frag
+++ b/shaders/cook_torrance.frag
@@ -152,8 +152,8 @@ vec3 cook_torrance_IBL(
     vec3 albedo, float metallic, float roughness, float occlusion,
     float NdotV,
     vec3 irradiance, vec3 prefiltered_env, vec2 BRDF_env) {
-  vec3 F0 = mix(vec3(0.04), albedo, metallic);
-  vec3  F = fresnel_schlick_roughness(F0, NdotV, roughness);
+  vec3 F0 = mix(vec3(0.04), albedo, metallic); // albedo = F0 for metals
+  vec3 F  = fresnel_schlick_roughness(F0, NdotV, roughness);
   vec3 Kd = (vec3(1.0) - F) * (1.0 - metallic);
   // A non-HDR environment map essentially has the 1/pi baked in as it does not
   // use physical units. See:
@@ -204,6 +204,11 @@ void main()
   // to use all maps.
   // https://sketchfab.com/models/b81008d513954189a063ff901f7abfe4
 #if HAS_NORMAL_MAP
+  // Spec: "After dequantization, texel values MUST be mapped as follows:
+  //   red   [0.0 .. 1.0] to X [-1 .. 1],
+  //   green [0.0 .. 1.0] to Y [-1 .. 1],
+  //   blue  (0.5 .. 1.0] to Z ( 0 .. 1].
+  // Normal textures SHOULD NOT contain blue values less than or equal to 0.5."
   vec3 normalMapSample = texture(NormalMap, Texcoord).xyz * 2.0 - 1.0;
   vec3 N = get_ws_normal(Normal, normalMapSample);
 #elif HAS_NORMALS
-- 
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