First implementation of model-triangle intersection

src/util/Model.cpp

@@ -1,6 +1,53 @@
 #include "Model.h"
 
-std::optional<IntersectionInfo> Model::intersect(Ray ray)
+std::optional<IntersectionInfo> Model::intersect(const Ray ray)
 {
-    return {};
+  std::optional<IntersectionInfo> intersection = {};
+  float distance = 0;
+
+  for(size_t posIndex=0, eIndex=0, normalIndex=0;  posIndex <indices.size(); posIndex+=3, eIndex+=2, normalIndex++)
+  {
+    const auto p0 = positions[posIndex];
+    const auto p1 = positions[posIndex +1];
+    const auto p2 = positions[posIndex +2];
+
+    const auto e0 = es[eIndex];
+    const auto e1 = es[eIndex +1];
+
+    const auto n = faceNormals[normalIndex];
+
+    const auto s = ray.origin - p0;
+    const auto s1 = glm::cross(ray.direction, e1);
+    const auto s2 = glm::cross(s, e0);
+
+    const float fraction = 1.0f / glm::dot(s1, e0);
+    const auto resultVector = glm::vec3(glm::dot(s2, e1), glm::dot(s1, s), glm::dot(s2, ray.direction)) * fraction;
+
+    const double b3 = 1 - resultVector.y - resultVector.z;
+
+    if(b3 < 0 || b3 > 1)
+      continue;
+    if(resultVector.y < 0 || resultVector.y > 1)
+      continue;
+    if(resultVector.z < 0 || resultVector.z > 1)
+      continue;
+
+    if(std::abs(1.0f - (resultVector.y + resultVector.z + b3)) > 1e-7)
+      continue;
+    if(resultVector.x < 1e-6)
+      continue;
+
+    if(!intersection.has_value() || resultVector.x < distance)
+    {
+      intersection = IntersectionInfo {
+        .position = ray.origin + ray.direction * resultVector.x,
+        .normal = n,
+        .albedo = glm::vec3(0.7f, 0.7f, 0.7f),
+        .emissive = glm::vec3(0.0f, 0.0f, 0.0f)
+      };
+      distance = resultVector.x;
+    }
+  }
+
+  return intersection;
 }

src/util/Model.h

@@ -22,6 +22,8 @@ public:
     AABB boundingBox;
 	std::vector<glm::vec3> positions;
 	std::vector<uint32_t> indices;
+        std::vector<glm::vec3> es;
+        std::vector<glm::vec3> faceNormals;
 	std::optional<IntersectionInfo> intersect(Ray ray);
 };
 DECLARE_REF(Model)

src/util/ModelLoader.cpp

@@ -27,6 +27,13 @@ std::vector<PModel> ModelLoader::loadModel(std::string_view filename)
             model->indices.push_back(face.mIndices[0]);
             model->indices.push_back(face.mIndices[1]);
             model->indices.push_back(face.mIndices[2]);
+
+            auto e0 = model->positions[face.mIndices[1] - face.mIndices[0]];
+            auto e1 = model->positions[face.mIndices[2] - face.mIndices[0]];
+            model->es.push_back(e0);
+            model->es.push_back(e1);
+
+            model->faceNormals.push_back(glm::cross(e0, e1));
         }
         model->boundingBox = aabb;
         result.push_back(std::move(model));