1.[ADD]:add reflect and refract function, and refract normal could be automatically flipped

Author: Liupeter01

include/Tools.hpp

@@ -152,6 +152,10 @@ struct Tools {
                                              const glm::vec3 &pb,
                                              const glm::vec3 &pc);
 
+  static glm::vec3 reflect(const glm::vec3& I, const glm::vec3& N);
+
+  static glm::vec3 refract(const glm::vec3& I, const glm::vec3& N, const float& ior);
+
   static float fresnel(const glm::vec3 &rayDirection, const glm::vec3 &normal,
                        const float &refractiveIndex);
 

src/Tools.cpp

@@ -247,6 +247,21 @@ glm::vec3 SoftRasterizer::Tools::calculateNormalWithWeight(
   return glm::normalize(normal);
 }
 
+glm::vec3 SoftRasterizer::Tools::reflect(const glm::vec3& I, const glm::vec3& N) {
+          return I - 2 * glm::dot(I, N) * N;
+}
+
+glm::vec3 SoftRasterizer::Tools::refract(const glm::vec3& I, const glm::vec3& N, const float& ior) {
+          float cosi = std::clamp(glm::dot(I, N), -1.f, 1.f);
+          float etai = 1.f, etat = ior;
+          glm::vec3 n = N;
+          if (cosi < 0) { cosi = -cosi; }
+          else { std::swap(etai, etat); n = -N; }
+          float eta = etai / etat;
+          float k = 1 - eta * eta * (1 - cosi * cosi);
+          return k < 0 ? glm::vec3(0.f) : eta * I + (eta * cosi - sqrtf(k)) * n;
+}
+
 float SoftRasterizer::Tools::fresnel(const glm::vec3 &rayDirection,
                                      const glm::vec3 &normal,
                                      const float &refractiveIndex) {