simplify

Author: dvicini

src/render/mesh.cpp

@@ -1549,16 +1549,16 @@ Mesh<Float, Spectrum>::compute_surface_interaction(const Ray3f &ray,
     }
 
     if (has_vertex_normals() && (m_shadow_offset_scale > 0.f)) {
-        Vector3f tmp0 = si.p - p0,
-                 tmp1 = si.p - p1,
-                 tmp2 = si.p - p2;
-        Float dot0 = dr::minimum(dr::dot(tmp0, n0), 0.0f),
-              dot1 = dr::minimum(dr::dot(tmp1, n1), 0.0f),
-              dot2 = dr::minimum(dr::dot(tmp2, n2), 0.0f);
-        tmp0 -= dot0 * n0;
-        tmp1 -= dot1 * n1;
-        tmp2 -= dot2 * n2;
-        si.shadow_offset = m_shadow_offset_scale * dr::fmadd(tmp0, b0, dr::fmadd(tmp1, b1, tmp2 * b2));
+        // Implements "Hacking the shadow terminator" by Johannes Hanika (2021).
+        // The code matches the original implementation, but was slightly simplified
+        // since b0 * p0 + b1 * p1 + b2 * p2 = si.p, and b0 + b1 + b2 = 1.
+        Vector3f tmp0 = p0 - si.p, tmp1 = p1 - si.p, tmp2 = p2 - si.p;
+        Float dot0 = dr::maximum(dr::dot(tmp0, n0), 0.f),
+              dot1 = dr::maximum(dr::dot(tmp1, n1), 0.f),
+              dot2 = dr::maximum(dr::dot(tmp2, n2), 0.f);
+        si.shadow_offset =
+            m_shadow_offset_scale *
+            dr::fmadd(b0, dot0 * n0, dr::fmadd(b1, dot1 * n1, b2 * dot2 * n2));
     }
 
     if (m_flip_normals) {