[CORE][ADD] Add hit API to Mesh

- Moller Trumbore algorithm is used

FinalProject/mesh.cpp

@@ -53,3 +53,38 @@ void Mesh::setupMesh() {
     //_vao.setVertexAttributePointer(3, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)OFFSETOF(Vertex, _tangent));
     //_vao.setVertexAttributePointer(4, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)OFFSETOF(Vertex, _bitangent));
 }
+
+HitRecord Mesh::hit(const Ray& ray) const {
+    // Test whether the ray hits the mesh
+    
+    // Traverse the indices to test every triangle
+    for (int i = 0; i < _indices.size(); i += 3) {
+        // Get the three vertices of the triangle
+        Vertex v0 = _vertices[_indices[i]];
+        Vertex v1 = _vertices[_indices[i + 1]];
+        Vertex v2 = _vertices[_indices[i + 2]];
+
+        // Moller Trumbore algorithm
+        // https://en.wikipedia.org/wiki/M%C3%B6ller%E2%80%93Trumbore_intersection_algorithm
+        glm::vec3 edge1 = v1._position - v0._position;
+        glm::vec3 edge2 = v2._position - v0._position;
+        glm::vec3 pvec = glm::cross(ray.direction(), edge2);
+        float det = glm::dot(edge1, pvec);
+        if (det < 0.0001f) continue;
+        float invDet = 1.0f / det;
+        glm::vec3 tvec = ray.origin() - v0._position;
+        float u = glm::dot(tvec, pvec) * invDet;
+        if (u < 0.0f || u > 1.0f) continue;
+        glm::vec3 qvec = glm::cross(tvec, edge1);
+        float v = glm::dot(ray.direction(), qvec) * invDet;
+        if (v < 0.0f || u + v > 1.0f) continue;
+        float t = glm::dot(edge2, qvec) * invDet;
+        if (t > 0.0001f) {
+            // Hit
+            glm::vec3 normal = glm::normalize(glm::cross(edge1, edge2));
+            glm::vec3 hitPoint = ray.origin() + t * ray.direction();
+            return HitRecord(hitPoint, normal);
+        }
+    }
+    return HitRecord();
+}

FinalProject/mesh.h

@@ -6,6 +6,8 @@
 #include "texture.h"
 #include "vao.h"
 #include "shader.h"
+#include "ray.h"
+#include "hitrecord.h"
 
 class Mesh {
 private:
@@ -34,6 +36,7 @@ public:
 
 public:
     void render(const ShaderProgram& shader) const ;
+    HitRecord hit(const Ray& ray) const;
 
 private:
     void setupMesh();