Update sheen to Zeltner 2022 / Blender 4.x

Author: tylertms

src/app/editor/inspector/scene.c

@@ -213,8 +213,8 @@ static void drawMeshMaterialEditor(VKRT* vkrt, uint32_t meshIndex, const VKRT_Me
     materialChanged |= ImGui_SliderFloatEx("Anisotropic", &material.anisotropic, 0.0f, 1.0f, "%.3f", ImGuiSliderFlags_AlwaysClamp);
     materialChanged |= ImGui_SliderFloatEx("Transmission", &material.transmission, 0.0f, 1.0f, "%.3f", ImGuiSliderFlags_AlwaysClamp);
     materialChanged |= ImGui_SliderFloatEx("Subsurface", &material.subsurface, 0.0f, 1.0f, "%.3f", ImGuiSliderFlags_AlwaysClamp);
-    materialChanged |= ImGui_SliderFloatEx("Sheen", &material.sheen, 0.0f, 1.0f, "%.3f", ImGuiSliderFlags_AlwaysClamp);
-    materialChanged |= ImGui_SliderFloatEx("Sheen Tint", &material.sheenTint, 0.0f, 1.0f, "%.3f", ImGuiSliderFlags_AlwaysClamp);
+    materialChanged |= ImGui_SliderFloatEx("Sheen Weight", &material.sheenTintWeight[3], 0.0f, 1.0f, "%.3f", ImGuiSliderFlags_AlwaysClamp);
+    materialChanged |= ImGui_ColorEdit3("Sheen Tint", material.sheenTintWeight, ImGuiColorEditFlags_Float);
     materialChanged |= ImGui_SliderFloatEx("Sheen Roughness", &material.sheenRoughness, 0.0f, 1.0f, "%.3f", ImGuiSliderFlags_AlwaysClamp);
     materialChanged |= ImGui_SliderFloatEx("Clearcoat", &material.clearcoat, 0.0f, 1.0f, "%.3f", ImGuiSliderFlags_AlwaysClamp);
     materialChanged |= ImGui_SliderFloatEx("Clearcoat Gloss", &material.clearcoatGloss, 0.0f, 1.0f, "%.3f", ImGuiSliderFlags_AlwaysClamp);

src/app/mesh/loader.c

@@ -457,12 +457,23 @@ static Material buildMaterial(const cgltf_material* sourceMaterial) {
     }
 
     if (sourceMaterial->has_sheen) {
-        material.sheen = max3(
+        vec3 sheenColor = {
             sourceMaterial->sheen.sheen_color_factor[0],
             sourceMaterial->sheen.sheen_color_factor[1],
             sourceMaterial->sheen.sheen_color_factor[2]
-        );
-        material.sheenTint = material.sheen > 0.0f ? 1.0f : 0.0f;
+        };
+        float sheenWeight = max3(sheenColor[0], sheenColor[1], sheenColor[2]);
+        if (sheenWeight > 0.0f) {
+            material.sheenTintWeight[0] = sheenColor[0] / sheenWeight;
+            material.sheenTintWeight[1] = sheenColor[1] / sheenWeight;
+            material.sheenTintWeight[2] = sheenColor[2] / sheenWeight;
+            material.sheenTintWeight[3] = sheenWeight;
+        } else {
+            material.sheenTintWeight[0] = 1.0f;
+            material.sheenTintWeight[1] = 1.0f;
+            material.sheenTintWeight[2] = 1.0f;
+            material.sheenTintWeight[3] = 0.0f;
+        }
         material.sheenRoughness = sourceMaterial->sheen.sheen_roughness_factor;
     }
 

src/core/api/mesh.c

@@ -10,6 +10,7 @@ static Material sanitizeMaterial(Material material) {
     for (int c = 0; c < 3; c++) {
         material.baseColor[c] = vkrtFiniteClampf(material.baseColor[c], 0.0f, 0.0f, 1.0f);
         material.emissionColor[c] = vkrtFiniteClampf(material.emissionColor[c], 0.0f, 0.0f, INFINITY);
+        material.sheenTintWeight[c] = vkrtFiniteClampf(material.sheenTintWeight[c], 0.0f, 0.0f, 1.0f);
     }
 
     material.metallic = vkrtFiniteClampf(material.metallic, 0.0f, 0.0f, 1.0f);
@@ -18,8 +19,7 @@ static Material sanitizeMaterial(Material material) {
     material.specular = vkrtFiniteClampf(material.specular, 0.0f, 0.0f, 1.0f);
     material.specularTint = vkrtFiniteClampf(material.specularTint, 0.0f, 0.0f, 1.0f);
     material.anisotropic = vkrtFiniteClampf(material.anisotropic, 0.0f, 0.0f, 1.0f);
-    material.sheen = vkrtFiniteClampf(material.sheen, 0.0f, 0.0f, 1.0f);
-    material.sheenTint = vkrtFiniteClampf(material.sheenTint, 0.0f, 0.0f, 1.0f);
+    material.sheenTintWeight[3] = vkrtFiniteClampf(material.sheenTintWeight[3], 0.0f, 0.0f, 1.0f);
     material.clearcoat = vkrtFiniteClampf(material.clearcoat, 0.0f, 0.0f, 1.0f);
     material.clearcoatGloss = vkrtFiniteClampf(material.clearcoatGloss, 0.0f, 0.0f, 1.0f);
     material.ior = vkrtFiniteClampf(material.ior, 1.0f, 1.0f, 4.0f);
@@ -53,8 +53,7 @@ static int materialsEqual(const Material* a, const Material* b) {
         a->anisotropic == b->anisotropic &&
         a->specular == b->specular &&
         a->specularTint == b->specularTint &&
-        a->sheen == b->sheen &&
-        a->sheenTint == b->sheenTint &&
+        materialComponentEqual(a->sheenTintWeight, b->sheenTintWeight, 4) &&
         a->clearcoat == b->clearcoat &&
         a->clearcoatGloss == b->clearcoatGloss &&
         a->ior == b->ior &&

src/core/api/vkrt_types.h

@@ -85,8 +85,7 @@ static inline Material VKRT_materialDefault(void) {
         .specular = 0.5f,
         .specularTint = 0.0f,
         .anisotropic = 0.0f,
-        .sheen = 0.0f,
-        .sheenTint = 0.5f,
+        .sheenTintWeight = {1.0f, 1.0f, 1.0f, 0.0f},
         .clearcoat = 0.0f,
         .clearcoatGloss = 1.0f,
         .ior = 1.5f,

src/shaders/bsdf/common.slang

@@ -120,19 +120,16 @@ float3 bsdfTintColor(float3 baseColor) {
     return baseColor / luminance;
 }
 
-float3 bsdfSheenTintColor(float3 baseColor) {
-    float maxComponent = max(baseColor.x, max(baseColor.y, baseColor.z));
-    if (maxComponent <= 0.0) {
-        return float3(1.0);
-    }
+float sheenWeight(Material material) {
+    return saturate(material.sheenTintWeight.w);
+}
 
-    float tintWeight = smoothstep(0.02, 0.1, maxComponent);
-    return lerp(float3(1.0), bsdfTintColor(baseColor), tintWeight);
+float3 sheenTint(Material material) {
+    return saturate(material.sheenTintWeight.xyz);
 }
 
 float3 bsdfSheenColor(Material material) {
-    float3 tint = lerp(float3(1.0), bsdfSheenTintColor(material.baseColor), saturate(material.sheenTint));
-    return tint * material.sheen * (1.0 - material.metallic) * (1.0 - material.transmission);
+    return sheenTint(material) * sheenWeight(material);
 }
 
 float3 bsdfTransmissionColor(Material material) {