add basic interreflections

src/lib.rs

@@ -242,6 +242,27 @@ impl Core {
 				]);
 			}
 		}
+		let mut hits2: Vec<Hit> = Vec::with_capacity(hits.len());
+		for hit in &hits {
+			let reflector = Lambertian;
+			let reflected = reflector.reflect(&mut prng, hit.normal, hit.incident.dir);
+			let ray = Ray::new(hit.incident.base, reflected);
+			let Some(hit2) = scene.trace_ray(ray) else {
+				continue;
+			};
+			hits2.push(hit2);
+			source_ray_display.extend([
+				Vertex {
+					pos: hit2.incident.base - 0.02 * hit2.incident.dir,
+					color: vec3(1., 0., 1.),
+				},
+				Vertex {
+					pos: hit2.incident.base,
+					color: vec3(1., 1., 1.),
+				},
+			]);
+		}
+		hits.extend(hits2);
 		let mut camera_ray_display: Vec<Vertex> = Vec::with_capacity(camera_rays.len());
 		let sigma2 = args.accum_sigma.powi(2);
 		let accum_normalizator = (2. * PI * sigma2).sqrt().recip();