From 4203391783a0d9912b3dbd6093898c1f991aa190 Mon Sep 17 00:00:00 2001
From: nullprop <git@nullprop.sh>
Date: Tue, 26 Dec 2023 20:23:40 +0200
Subject: [PATCH] Better ambient light estimation

---
 res/shaders/constants.wgsl |  2 --
 res/shaders/fog.wgsl       | 12 ++++++------
 res/shaders/light.wgsl     | 17 +++++++++++++++++
 res/shaders/pbr.wgsl       | 30 +++++++++++++++++-------------
 4 files changed, 40 insertions(+), 21 deletions(-)

diff --git a/res/shaders/constants.wgsl b/res/shaders/constants.wgsl
index bbb3eed..98f3424 100644
--- a/res/shaders/constants.wgsl
+++ b/res/shaders/constants.wgsl
@@ -14,7 +14,5 @@ const FOG_LIGHT_STEP_SIZE = 10.0;
 const FOG_DENSITY = 2.0;
 const FOG_LIGHT_DENSITY = 3.0;
 const FOG_ALPHA = 1.0;
-const FOG_AMBIENT = 0.06;
 const FOG_DENSITY_COLOR = vec2<f32>(0.5, 0.1);
 
-const PBR_AMBIENT = 0.02;
diff --git a/res/shaders/fog.wgsl b/res/shaders/fog.wgsl
index df2b956..e57c7f8 100644
--- a/res/shaders/fog.wgsl
+++ b/res/shaders/fog.wgsl
@@ -140,24 +140,24 @@ fn fs_main(vert: FogVertexOutput) -> @location(0) vec4<f32> {
     let fog_depth = march_result.y;
     let occlusion = march_result.z;
 
+    let fog_position = vert.world_position.xyz + direction * fog_depth;
+    let light_dist = length(light.position - fog_position);
+
     let base_color = vec3<f32>(mix(FOG_DENSITY_COLOR.x, FOG_DENSITY_COLOR.y, fog_density));
-    let ambient_strength = FOG_AMBIENT;
-    let ambient_color = base_color * ambient_strength;
+    var ambient = 2.0 * sample_ambient_light(light.color, light_dist, 1.0);
+    ambient *= base_color;
 
     var radiance = vec3<f32>(0.0);
-    let fog_position = vert.world_position.xyz + direction * fog_depth;
     let in_light = sample_direct_light(vec4<f32>(fog_position, 1.0));
     if (in_light > 0.0) {
         // attenuation
-        let light_dist = length(light.position - fog_position);
         let coef_a = 0.0;
         let coef_b = 1.0;
         let light_attenuation = 1.0 / (1.0 + coef_a * light_dist + coef_b * light_dist * light_dist);
-
         radiance = light.color.rgb * light.color.a * light_attenuation * in_light * (1.0 - occlusion);
     }
 
-    var result = ambient_color + radiance;
+    var result = ambient + radiance;
 
     // tonemap
     result = result / (result + vec3(1.0));
diff --git a/res/shaders/light.wgsl b/res/shaders/light.wgsl
index ed6f743..d0971e7 100644
--- a/res/shaders/light.wgsl
+++ b/res/shaders/light.wgsl
@@ -59,3 +59,20 @@ fn sample_direct_light(world_position: vec4<f32>) -> f32 {
     }
     return in_light;
 }
+
+fn sample_ambient_light(light: vec4<f32>, light_dist: f32, surface_light_dot: f32) -> vec3<f32> {
+    // base ambient
+    var ambient = vec3(0.01);
+
+    // lower attenuation to reduce light bleed
+    let diff_coef_a = -0.75;
+    let diff_coef_b = 0.25;
+    let diff_light_attenuation = 1.0 / (1.0 + diff_coef_a * light_dist + diff_coef_b * light_dist * light_dist);
+    let diff_direct_light = light.rgb * light.a * diff_light_attenuation;
+
+    // very rough bounce light estimation
+    let diffuse_mult = max(surface_light_dot, 0.0);
+    ambient += diffuse_mult * 0.03 * diff_direct_light;
+
+    return ambient;
+}
diff --git a/res/shaders/pbr.wgsl b/res/shaders/pbr.wgsl
index 56cb5d7..5122337 100644
--- a/res/shaders/pbr.wgsl
+++ b/res/shaders/pbr.wgsl
@@ -84,23 +84,27 @@ fn fs_main(vert: VertexOutput) -> @location(0) vec4<f32> {
 
     var total_radiance: vec3<f32>;
 
+    let normal_dir = tex_normal.xyz * 2.0 - 1.0;
+    var light_dir = normalize(vert.tangent_light_position - vert.tangent_position);
+    let surface_light_dot = dot(normal_dir, light_dir);
+    let light_dist = length(light.position - vert.world_position.xyz);
+
+    // attenuation
+    let coef_a = 0.0;
+    let coef_b = 1.0;
+    let light_attenuation = 1.0 / (1.0 + coef_a * light_dist + coef_b * light_dist * light_dist);
+
+    let direct_light = light.color.rgb * light.color.a * light_attenuation;
+
     let in_light = sample_direct_light(vert.world_position);
     if (in_light > 0.0) {
         // lighting vecs
-        let normal_dir = tex_normal.xyz * 2.0 - 1.0;
-        var light_dir = normalize(vert.tangent_light_position - vert.tangent_position);
         let view_dir = normalize(vert.tangent_view_position - vert.tangent_position);
         let half_dir = normalize(view_dir + light_dir);
 
-        // attenuation
-        let light_dist = length(light.position - vert.world_position.xyz);
-        let coef_a = 0.0;
-        let coef_b = 1.0;
-        let light_attenuation = 1.0 / (1.0 + coef_a * light_dist + coef_b * light_dist * light_dist);
-
         // radiance
-        let radiance_strength = max(dot(normal_dir, light_dir), 0.0);
-        let radiance = radiance_strength * light.color.rgb * light.color.a * light_attenuation * in_light;
+        let radiance_strength = max(surface_light_dot, 0.0);
+        let radiance = radiance_strength * direct_light * in_light;
 
         // brdf shading
         total_radiance += radiance * brdf(
@@ -114,10 +118,10 @@ fn fs_main(vert: VertexOutput) -> @location(0) vec4<f32> {
         );
     }
 
-    // ambient
-    let ambient_color = PBR_AMBIENT * albedo;
+    var ambient = sample_ambient_light(light.color, light_dist, surface_light_dot);
+    ambient *= albedo;
 
-    var result = ambient_color + total_radiance;
+    var result = ambient + total_radiance;
 
     // tonemap
     result = result / (result + vec3(1.0));