Added WIP implementation

shader/brdfshader.cpp

@@ -7,7 +7,51 @@ BrdfShader::BrdfShader(char const *fileName, Color const &scale)
 
 Color BrdfShader::shade(Scene const &scene, Ray const &ray) const {
     Color illuminationColor;
+    static auto rebase = [](Vector3d const &axis_x,
+                            Vector3d const &axis_y,
+                            Vector3d const &axis_z,
+                            Vector3d const &vec) {
+        auto det = axis_x.x * axis_y.y * axis_z.z +
+                   axis_x.y * axis_y.z * axis_z.x +
+                   axis_x.z * axis_y.x * axis_z.y -
+                   axis_x.x * axis_y.z * axis_z.y -
+                   axis_x.y * axis_y.x * axis_z.z -
+                   axis_x.z * axis_y.y * axis_z.x;
+        // Calculate resulting vector by using inverse matrix of new base vectors
+        return Vector3d{
+                ((axis_y.y * axis_z.z - axis_y.z * axis_z.y) * vec.x +
+                 (axis_y.z * axis_z.x - axis_y.x * axis_z.z) * vec.y +
+                 (axis_y.x * axis_z.y - axis_y.y * axis_z.x) * vec.z) / det,
+                ((axis_x.z * axis_z.y - axis_x.y * axis_z.z) * vec.x +
+                 (axis_x.x * axis_z.z - axis_x.x * axis_y.z) * vec.y +
+                 (axis_x.y * axis_z.x - axis_x.x * axis_y.x) * vec.z) / det,
+                ((axis_x.y * axis_y.z - axis_x.z * axis_y.y) * vec.x +
+                 (axis_x.z * axis_y.x - axis_x.x * axis_y.z) * vec.y +
+                 (axis_x.x * axis_y.y - axis_x.y * axis_y.x) * vec.z) / det
+        };
 
+    };
+
+    for (auto &light: scene.lights()) {
+
+        auto illum = light->illuminate(scene, ray);
+
+        auto axis = orthoNormalized(ray.normal, ray.direction, illum.direction);
+        auto axis_y = std::get<0>(axis);
+        auto axis_x = std::get<1>(axis);
+        auto axis_z = std::get<2>(axis);
+
+        auto N = normalized(rebase(axis_x, axis_y, axis_z, ray.normal));
+        auto D = normalized(rebase(axis_x, axis_y, axis_z, ray.direction));
+        auto L = normalized(rebase(axis_x, axis_y, axis_z, illum.direction));
+        D = axis_y * D.y + axis_z * D.z;
+        L = axis_y * L.y + axis_z * L.z;
+
+        illuminationColor += brdf->lookupBrdfValues(std::acos(dotProduct(illum.direction, ray.normal)),
+                                                    0,
+                                                    std::acos(dotProduct(ray.direction, ray.normal)),
+                                                    std::acos(dotProduct(D, L)));
+    }
     // IMPLEMENT ME
     return illuminationColor;
 }