Merge pull request #25 from MatchaChoco010/include-cos-term-into-bsdf

Include cosine term in BSDF calculations

Author: MatchaChoco010

renderer/src/renderer/base_renderer.rs

@@ -103,10 +103,9 @@ impl<'a, Id: SceneId, F: Filter, T: ToneMap, Strategy: RenderingStrategy>
             return None;
         }
 
-        let cos_theta = material_sample.normal.dot(material_sample.wi).abs();
         let sample_wi = material_sample.wi;
         let f_value = &material_sample.f;
-        let throughput_factor = cos_theta / material_sample.pdf;
+        let throughput_factor = 1.0 / material_sample.pdf;
 
         // wiの方向にレイを飛ばす
         let wi_render = &render_to_tangent.inverse() * &sample_wi;

renderer/src/renderer/common.rs

@@ -43,12 +43,9 @@ pub fn evaluate_delta_point_light<Id: SceneId>(
         let shading_point_tangent = render_to_tangent * shading_point;
         let material_result = bsdf.evaluate(lambda, &wo, &wi, &shading_point_tangent);
 
-        // Normal mappingされた表面法線に対するcos項
         let distance_squared = distance_vector.length_squared();
-        let cos_theta = material_result.normal.dot(wi).abs();
 
-        material_result.f * &intensity.intensity * cos_theta
-            / (distance_squared * light_probability)
+        material_result.f * &intensity.intensity / (distance_squared * light_probability)
     } else {
         SampledSpectrum::zero()
     }
@@ -75,10 +72,7 @@ pub fn evaluate_delta_directional_light<Id: SceneId>(
         let shading_point_tangent = render_to_tangent * shading_point;
         let material_result = bsdf.evaluate(lambda, &wo, &wi, &shading_point_tangent);
 
-        // Normal mappingされた表面法線に対するcos項
-        let cos_theta = material_result.normal.dot(wi).abs();
-
-        material_result.f * &intensity.intensity * cos_theta / light_probability
+        material_result.f * &intensity.intensity / light_probability
     } else {
         SampledSpectrum::zero()
     }
@@ -113,12 +107,11 @@ pub fn evaluate_area_light<Id: SceneId>(
         let material_result =
             bsdf.evaluate(lambda, &wo_tangent, &wi_tangent, &shading_point_tangent);
 
-        // 幾何項の計算
+        // 幾何項の計算（シェーディングポイント側のコサイン項はBSDFに含まれるため別途計算不要）
         let distance2 = distance_vector.length_squared();
         let light_normal = render_to_tangent * radiance.light_normal; // VertexNormalTangent座標系に変換
-        let cos_material = material_result.normal.dot(wi_tangent).abs(); // VertexNormalTangent座標系で統一
         let cos_light = light_normal.dot(-wi_tangent).abs(); // VertexNormalTangent座標系で統一
-        let g = cos_material * cos_light / distance2;
+        let g = cos_light / distance2;
 
         material_result.f * &radiance.radiance * g / (pdf * light_probability)
     } else {
@@ -153,12 +146,11 @@ pub fn evaluate_area_light_with_mis<Id: SceneId>(
         let pdf = radiance.pdf;
         let material_result = bsdf.evaluate(lambda, &wo, &wi, &shading_point_tangent);
 
-        // 幾何項の計算
+        // 幾何項の計算（シェーディングポイント側のコサイン項はBSDFに含まれるため別途計算不要）
         let distance2 = distance_vector.length_squared();
         let light_normal = render_to_tangent * radiance.light_normal;
-        let cos_material = material_result.normal.dot(wi).abs();
         let cos_light = light_normal.dot(-wi).abs();
-        let g = cos_material * cos_light / distance2;
+        let g = cos_light / distance2;
 
         // MISのウエイトを計算
         let pdf_light_dir = radiance.pdf_dir;
@@ -200,9 +192,7 @@ pub fn evaluate_infinite_light<Id: SceneId>(
         let shading_point_tangent = render_to_tangent * shading_point;
         let material_result = bsdf.evaluate(lambda, &wo, &wi, &shading_point_tangent);
 
-        let cos_theta = material_result.normal.dot(wi).abs();
-
-        material_result.f * &radiance_sample.radiance * cos_theta
+        material_result.f * &radiance_sample.radiance
             / (radiance_sample.pdf_dir * light_probability)
     } else {
         SampledSpectrum::zero()
@@ -231,14 +221,12 @@ pub fn evaluate_infinite_light_with_mis<Id: SceneId>(
         let shading_point_tangent = render_to_tangent * shading_point;
         let material_result = bsdf.evaluate(lambda, &wo, &wi, &shading_point_tangent);
 
-        let cos_theta = material_result.normal.dot(wi).abs();
-
         let pdf_light_dir = radiance_sample.pdf_dir;
         let pdf_bsdf_dir = bsdf.pdf(lambda, &wo, &wi, &shading_point_tangent);
         let mis_weight = balance_heuristic(pdf_light_dir, pdf_bsdf_dir);
 
-        let contribution = material_result.f * &radiance_sample.radiance * cos_theta
-            / (pdf_light_dir * light_probability);
+        let contribution =
+            material_result.f * &radiance_sample.radiance / (pdf_light_dir * light_probability);
 
         NeeResult {
             contribution,

renderer/src/renderer/mis_renderer.rs

@@ -223,8 +223,7 @@ impl RenderingStrategy for MisStrategy {
         let mis_weight = balance_heuristic(bsdf_pdf, light_pdf);
 
         // BSDF項を計算
-        let cos_theta = material_sample.normal.dot(material_sample.wi).abs();
-        let throughput_factor = cos_theta / material_sample.pdf;
+        let throughput_factor = 1.0 / material_sample.pdf;
 
         *sample_contribution +=
             throughput * &material_sample.f * radiance * throughput_factor * mis_weight;

renderer/src/renderer/normal_renderer.rs

@@ -2,7 +2,6 @@
 
 use color::{ColorSrgb, tone_map};
 use scene::{Intersection, SceneId};
-use spectrum::SampledWavelengths;
 
 use crate::{
     filter::Filter,
@@ -41,27 +40,16 @@ impl<'a, Id: SceneId, F: Filter> Renderer for NormalRenderer<'a, Id, F> {
             let uv = sampler.get_2d_pixel();
             let rs = camera.sample_ray(p, uv);
 
-            // dummyのlambda
-            let u = sampler.get_1d();
-            let mut lambda = SampledWavelengths::new_uniform(u);
-
             let intersect = scene.intersect(&rs.ray, f32::MAX);
 
             let color = match intersect {
                 Some(intersect) => {
-                    let Intersection {
-                        interaction, wo, ..
-                    } = intersect;
+                    let Intersection { interaction, .. } = intersect;
                     let render_to_tangent = interaction.shading_transform();
-                    let wo = &render_to_tangent * wo;
                     let shading_point = &render_to_tangent * &interaction;
 
-                    if let Some(bsdf) = interaction.material.as_bsdf_material() {
-                        let uc = sampler.get_1d();
-                        let uv = sampler.get_2d();
-                        let material_sample = bsdf.sample(uc, uv, &mut lambda, &wo, &shading_point);
-                        let normal = material_sample.normal;
-                        let normal = render_to_tangent.inverse() * normal;
+                    if let Some(_bsdf) = interaction.material.as_bsdf_material() {
+                        let normal = shading_point.shading_normal;
                         glam::Vec3::new(
                             normal.x() * 0.5 + 0.5,
                             normal.y() * 0.5 + 0.5,

renderer/src/renderer/pt_renderer.rs

@@ -78,9 +78,7 @@ impl RenderingStrategy for PtStrategy {
 
         // 無限光源の放射輝度をBSDFで重み付けして計算
         let radiance = scene.evaluate_infinite_light_radiance(&background_ray, lambda);
-        let cos_theta = material_sample.normal.dot(material_sample.wi).abs();
-        *sample_contribution +=
-            throughput * &material_sample.f * radiance * cos_theta / material_sample.pdf;
+        *sample_contribution += throughput * &material_sample.f * radiance / material_sample.pdf;
     }
 }
 

renderer/tests/regression_test.rs

@@ -349,7 +349,7 @@ fn regression_test_scene7_pt_random() {
         7,
         "pt",
         "random",
-        512,
+        1024,
         "output.test_scene7_pt_random.png",
         "test_references/reference_scene7_pt_random.png",
         0.05,
@@ -362,7 +362,7 @@ fn regression_test_scene7_pt_sobol() {
         7,
         "pt",
         "sobol",
-        512,
+        1024,
         "output.test_scene7_pt_sobol.png",
         "test_references/reference_scene7_pt_sobol.png",
         0.05,

scene/src/material/bsdf.rs

@@ -42,7 +42,7 @@ pub enum ScatterMode {
 // Bsdfのサンプリング結果を表す構造体。
 #[derive(Debug, Clone)]
 pub struct BsdfSample {
-    /// BSDF値
+    /// BSDF値（コサイン項込み）
     pub f: spectrum::SampledSpectrum,
     /// サンプルされた入射方向（ノーマルマップ接空間）
     pub wi: math::Vector3<ShadingNormalTangent>,

scene/src/material/bsdf/conductor.rs

@@ -283,8 +283,8 @@ impl ConductorBsdf {
         // Fresnel反射率を計算
         let fresnel = fresnel_complex(wi_cos_n.abs(), &self.eta, &self.k);
 
-        // BSDF値: F / |cos(theta_i)|
-        let f = fresnel / wi_cos_n.abs();
+        // BSDF値: F (Specularではcosine項の操作なし)
+        let f = fresnel;
 
         Some(BsdfSample::new(
             f,
@@ -346,8 +346,8 @@ impl ConductorBsdf {
         // マスキング・シャドウイング項: G(ωo, ωi)
         let masking_shadowing = self.masking_shadowing_g(wo, wi);
 
-        // Torrance-Sparrow BRDF: D(ωm) * F(ωo·ωm) * G(ωo, ωi) / (4 * cos θi * cos θo)
-        fresnel * distribution * masking_shadowing / (4.0 * cos_theta_i * cos_theta_o)
+        // Torrance-Sparrow BRDF（cosine項を含む）: D(ωm) * F(ωo·ωm) * G(ωo, ωi) / (4 * cos θo)
+        fresnel * distribution * masking_shadowing / (4.0 * cos_theta_o)
     }
 
     /// BSDF値を評価する。

scene/src/material/bsdf/dielectric.rs

@@ -312,10 +312,10 @@ impl DielectricBsdf {
         }
         let pdf = self.visible_normal_distribution(wo, wm) / (4.0 * cos_theta_dot) * prob;
 
-        // BRDF値計算
+        // BRDF値計算（cosine項を含む）
         let d = self.microfacet_distribution(wm);
         let g = self.masking_shadowing_g(wo, &wi);
-        let f_value = fresnel * d * g / (4.0 * abs_cos_theta(&wi) * abs_cos_theta(wo));
+        let f_value = fresnel * d * g * abs_cos_theta(&wi) / (4.0 * abs_cos_theta(wo));
 
         Some(BsdfSample::new(
             f_value,
@@ -349,11 +349,10 @@ impl DielectricBsdf {
 
         let d = self.microfacet_distribution(wm);
         let g = self.masking_shadowing_g(wo, &wi);
-        let cos_theta_i = abs_cos_theta(&wi);
         let cos_theta_o = abs_cos_theta(wo);
 
         let ft = transmission * d * g * wi.dot(wm).abs() * wo.dot(wm).abs()
-            / (denom * cos_theta_i * cos_theta_o * etap * etap);
+            / (denom * cos_theta_o * etap * etap);
 
         Some(BsdfSample::new(
             ft,
@@ -379,8 +378,7 @@ impl DielectricBsdf {
         let pdf = prob;
 
         // BTDF値（thin surfaceの特別な処理）
-        let wi_cos_n = abs_cos_theta(&wi);
-        let f_value = transmission / wi_cos_n;
+        let f_value = transmission;
 
         Some(BsdfSample::new(
             f_value,
@@ -453,7 +451,7 @@ impl DielectricBsdf {
                 if wo_cos_n.abs() < 1e-6 {
                     return None;
                 }
-                let f = fresnel / wo_cos_n.abs();
+                let f = fresnel;
                 Some(BsdfSample::new(
                     f,
                     wi,
@@ -470,7 +468,7 @@ impl DielectricBsdf {
 
                 // Thin surfaceの場合、放射輝度のスケーリングは不要（同じ媒質に戻るため）
                 let transmission = SampledSpectrum::one() - fresnel;
-                let f = transmission / wi_cos_n.abs();
+                let f = transmission;
                 Some(BsdfSample::new(
                     f,
                     wi,
@@ -490,7 +488,7 @@ impl DielectricBsdf {
                 if wo_cos_n.abs() < 1e-6 {
                     return None;
                 }
-                let f = fresnel / wo_cos_n.abs();
+                let f = fresnel;
                 Some(BsdfSample::new(
                     f,
                     wi,
@@ -510,7 +508,7 @@ impl DielectricBsdf {
                     }
 
                     let transmission = SampledSpectrum::one() - fresnel;
-                    let f = transmission / (etap_scalar.powi(2) * wt_cos_n.abs());
+                    let f = transmission / etap_scalar.powi(2);
                     Some(BsdfSample::new(
                         f,
                         wt,
@@ -588,15 +586,15 @@ impl DielectricBsdf {
             let d = self.microfacet_distribution(&wm);
             let g = self.masking_shadowing_g(wo, wi);
 
-            fresnel * d * g / (4.0 * abs_cos_theta(wi) * abs_cos_theta(wo))
+            fresnel * d * g / (4.0 * abs_cos_theta(wo))
         } else {
             let denom = (wi.dot(wm) + wo.dot(wm) / eta_scalar).powi(2);
             let d = self.microfacet_distribution(&wm);
             let g = self.masking_shadowing_g(wo, wi);
             let transmission = SampledSpectrum::one() - fresnel;
 
             transmission * d * g * wi.dot(wm).abs() * wo.dot(wm).abs()
-                / (denom * abs_cos_theta(wi) * abs_cos_theta(wo) * eta_scalar * eta_scalar)
+                / (denom * abs_cos_theta(wo) * eta_scalar * eta_scalar)
         }
     }