Update diffuse material to support roughness parameter

Author: Sopiro

include/bulbit/bxdfs.h

@@ -565,7 +565,7 @@ class EONBxDF : public BxDF
     // EON: APractical Energy-Preserving Rough Diffuse BRDF (Portsmouth et al., 2025)
     // https://jcgt.org/published/0014/01/06/
 public:
-    EONBxDF(const Spectrum& reflectance, Float roughness = 0, bool exact = true)
+    EONBxDF(const Spectrum& reflectance, Float roughness, bool exact = true)
         : rho{ reflectance }
         , r{ roughness }
         , exact{ exact }

include/bulbit/materials.h

@@ -9,7 +9,10 @@ class DiffuseMaterial : public Material
 {
 public:
     DiffuseMaterial(
-        const SpectrumTexture* reflectance, const SpectrumTexture* normalmap = nullptr, const FloatTexture* alpha = nullptr
+        const SpectrumTexture* reflectance,
+        const FloatTexture* roughness = nullptr,
+        const SpectrumTexture* normalmap = nullptr,
+        const FloatTexture* alpha = nullptr
     );
 
     Float GetAlpha(const Intersection& isect) const;
@@ -21,6 +24,7 @@ class DiffuseMaterial : public Material
 
 public:
     const SpectrumTexture* reflectance;
+    const FloatTexture* roughness;
 
     const SpectrumTexture* normalmap;
     const FloatTexture* alpha;

sample/material_builder.cpp

@@ -4,23 +4,29 @@
 namespace bulbit
 {
 
-DiffuseMaterial* CreateDiffuseMaterial(Scene& scene, Float reflectance, const SpectrumTexture* normalmap, Float alpha)
+DiffuseMaterial* CreateDiffuseMaterial(
+    Scene& scene, Float reflectance, Float roughness, const SpectrumTexture* normalmap, Float alpha
+)
 {
     return scene.CreateMaterial<DiffuseMaterial>(
-        CreateSpectrumConstantTexture(scene, reflectance), normalmap, CreateFloatConstantTexture(scene, alpha)
+        CreateSpectrumConstantTexture(scene, reflectance), CreateFloatConstantTexture(scene, roughness), normalmap,
+        CreateFloatConstantTexture(scene, alpha)
     );
 }
-DiffuseMaterial* CreateDiffuseMaterial(Scene& scene, const Spectrum& reflectance, const SpectrumTexture* normalmap, Float alpha)
+DiffuseMaterial* CreateDiffuseMaterial(
+    Scene& scene, const Spectrum& reflectance, Float roughness, const SpectrumTexture* normalmap, Float alpha
+)
 {
     return scene.CreateMaterial<DiffuseMaterial>(
-        CreateSpectrumConstantTexture(scene, reflectance), normalmap, CreateFloatConstantTexture(scene, alpha)
+        CreateSpectrumConstantTexture(scene, reflectance), CreateFloatConstantTexture(scene, roughness), normalmap,
+        CreateFloatConstantTexture(scene, alpha)
     );
 }
 
 DiffuseMaterial* CreateDiffuseMaterial(Scene& scene, const std::string& filename, const SpectrumTexture* normalmap, Float alpha)
 {
     return scene.CreateMaterial<DiffuseMaterial>(
-        CreateSpectrumImageTexture(scene, filename), normalmap, CreateFloatConstantTexture(scene, alpha)
+        CreateSpectrumImageTexture(scene, filename), nullptr, normalmap, CreateFloatConstantTexture(scene, alpha)
     );
 }
 

sample/material_builder.h

@@ -7,10 +7,10 @@ namespace bulbit
 {
 
 DiffuseMaterial* CreateDiffuseMaterial(
-    Scene& scene, Float reflectance, const SpectrumTexture* normalmap = nullptr, Float alpha = 1
+    Scene& scene, Float reflectance, Float roughness = 0, const SpectrumTexture* normalmap = nullptr, Float alpha = 1
 );
 DiffuseMaterial* CreateDiffuseMaterial(
-    Scene& scene, const Spectrum& reflectance, const SpectrumTexture* normalmap = nullptr, Float alpha = 1
+    Scene& scene, const Spectrum& reflectance, Float roughness = 0, const SpectrumTexture* normalmap = nullptr, Float alpha = 1
 );
 DiffuseMaterial* CreateDiffuseMaterial(
     Scene& scene, const std::string& filename, const SpectrumTexture* normalmap = nullptr, Float alpha = 1

sample/scene/material_test.cpp

@@ -425,9 +425,9 @@ std::unique_ptr<Camera> Alphas(Scene& scene)
     auto normalmap = CreateSpectrumImageTexture(scene, "res/bistro/Concrete_Normal.png", true);
 
     const Material* outers[count];
-    outers[0] = CreateDiffuseMaterial(scene, Spectrum(.65f, .05f, .05f), nullptr, 0.4f);
-    outers[1] = CreateDiffuseMaterial(scene, Spectrum(.12f, .45f, .15f), nullptr, 0.2f);
-    outers[2] = CreateDiffuseMaterial(scene, Spectrum(.22f, .23f, .75f), nullptr, 0.6f);
+    outers[0] = CreateDiffuseMaterial(scene, Spectrum(.65f, .05f, .05f), 0, nullptr, 0.4f);
+    outers[1] = CreateDiffuseMaterial(scene, Spectrum(.12f, .45f, .15f), 0, nullptr, 0.2f);
+    outers[2] = CreateDiffuseMaterial(scene, Spectrum(.22f, .23f, .75f), 0, nullptr, 0.6f);
 
     const Material* inners[count];
     inners[0] = CreateMetallicRoughnessMaterial(scene, Spectrum{ 0.66 }, (0), (0));

src/material/diffuse_material.cpp

@@ -5,9 +5,12 @@
 namespace bulbit
 {
 
-DiffuseMaterial::DiffuseMaterial(const SpectrumTexture* reflectance, const SpectrumTexture* normalmap, const FloatTexture* alpha)
+DiffuseMaterial::DiffuseMaterial(
+    const SpectrumTexture* reflectance, const FloatTexture* roughness, const SpectrumTexture* normalmap, const FloatTexture* alpha
+)
     : Material(TypeIndexOf<DiffuseMaterial>())
     , reflectance{ reflectance }
+    , roughness{ roughness }
     , normalmap{ normalmap }
     , alpha{ alpha }
 {
@@ -40,7 +43,19 @@ Spectrum DiffuseMaterial::Le(const Intersection& isect, const Vec3& wo) const
 bool DiffuseMaterial::GetBSDF(BSDF* bsdf, const Intersection& isect, const Vec3& wo, Allocator& alloc) const
 {
     BulbitNotUsed(wo);
-    *bsdf = BSDF(isect.shading.normal, isect.shading.tangent, alloc.new_object<LambertianBxDF>(reflectance->Evaluate(isect.uv)));
+
+    Float r = roughness ? roughness->Evaluate(isect.uv) : 0;
+    Spectrum rho = reflectance->Evaluate(isect.uv);
+
+    if (r > 0)
+    {
+        *bsdf = BSDF(isect.shading.normal, isect.shading.tangent, alloc.new_object<EONBxDF>(rho, r));
+    }
+    else
+    {
+        *bsdf = BSDF(isect.shading.normal, isect.shading.tangent, alloc.new_object<LambertianBxDF>(rho));
+    }
+
     return true;
 }