add more to notes13

Author: lumixraku

task5/task5/task5.xcodeproj/project.xcworkspace/xcuserdata/lilin.xcuserdatad/UserInterfaceState.xcuserstate

@@ -7,16 +7,16 @@
       <BreakpointProxy
          BreakpointExtensionID = "Xcode.Breakpoint.FileBreakpoint">
          <BreakpointContent
-            uuid = "B81C8E48-F2F4-4CC9-96B5-8C9E67FDA84E"
+            uuid = "A6B7847D-653A-4307-8168-E26F3DD812B4"
             shouldBeEnabled = "No"
             ignoreCount = "0"
             continueAfterRunningActions = "No"
             filePath = "task5/Renderer.cpp"
             startingColumnNumber = "9223372036854775807"
             endingColumnNumber = "9223372036854775807"
-            startingLineNumber = "96"
-            endingLineNumber = "96"
-            landmarkName = "trace(orig, dir, objects)"
+            startingLineNumber = "154"
+            endingLineNumber = "154"
+            landmarkName = "castRay(orig, dir, scene, depth)"
             landmarkType = "9">
          </BreakpointContent>
       </BreakpointProxy>

task5/task5/task5.xcodeproj/xcuserdata/lilin.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist

@@ -46,6 +46,12 @@ Vector3f refract(const Vector3f &I, const Vector3f &N, const float &ior)
 //
 // \param ior is the material refractive index
 // [/comment]
+
+
+// 菲涅耳方程（Fresnel equation）描述了光线经过两个介质的界面时，反射和透射的光强比重。
+// 参考 https://www.zhihu.com/question/53022233
+// https : //zhuanlan.zhihu.com/p/31534769
+// snell law n1*sinθ1=n2*sinθ2；
 float fresnel(const Vector3f &I, const Vector3f &N, const float &ior)
 {
     float cosi = clamp(-1, 1, dotProduct(I, N));
@@ -87,16 +93,20 @@ std::optional<hit_payload> trace(
     float tNear = kInfinity;
     std::optional<hit_payload> payload;
 
-    // 
     for (const auto & object : objects)
     {
         float tNearK = kInfinity;
         uint32_t indexK;
         Vector2f uvK;
 
         // 调用的三角形 OR 球体 intersect 方法
+        // intersect 中每个参数都是引用传递
+        // 注意tNearK < tNear 经过循环后得到的是最近的相交物体
         if (object->intersect(orig, dir, tNearK, indexK, uvK) && tNearK < tNear)
         {
+            // 这个 emplace 是 std::optional 下的函数
+            // https://en.cppreference.com/w/cpp/utility/optional/emplace  
+            // 看起来很像构造函数
             payload.emplace();
             payload->hit_obj = object.get();
             payload->tNear = tNearK;
@@ -124,6 +134,8 @@ std::optional<hit_payload> trace(
 // If the surface is diffuse/glossy we use the Phong illumation model to compute the color
 // at the intersection point.
 // [/comment]
+
+// castRay 就是递归的过程
 Vector3f castRay(
         const Vector3f &orig, const Vector3f &dir, const Scene& scene,
         int depth)
@@ -133,17 +145,31 @@ Vector3f castRay(
     }
 
     Vector3f hitColor = scene.backgroundColor;
+
+    // payload 类型是 hit_payload  trace 是获取碰撞点的详情
     if (auto payload = trace(orig, dir, scene.get_objects()); payload)
     {
         Vector3f hitPoint = orig + dir * payload->tNear;
         Vector3f N; // normal
         Vector2f st; // st coordinates
+
+        // getSurfaceProperties 
+        // getSurfaceProperties 所有参数都是引用传递  但实际上只有 st N 被写入了值
+        // st 是纹理坐标 (重心坐标系统) N是三角形面的法线
         payload->hit_obj->getSurfaceProperties(hitPoint, dir, payload->index, payload->uv, N, st);
         switch (payload->hit_obj->materialType) {
+
+            // 如果ray 射出到了玻璃球体
             case REFLECTION_AND_REFRACTION:
-            {
+            {   
+                // 反射方向
                 Vector3f reflectionDirection = normalize(reflect(dir, N));
+                
+                // 折射方向
                 Vector3f refractionDirection = normalize(refract(dir, N, payload->hit_obj->ior));
+                
+                // 注意在castRay 一开始定义ray dir 的时候 z 是 -1
+                // 点乘 > 0 hitPoint 会变大 看起来是略微向摄像机的位置移动了一点
                 Vector3f reflectionRayOrig = (dotProduct(reflectionDirection, N) < 0) ?
                                              hitPoint - N * scene.epsilon :
                                              hitPoint + N * scene.epsilon;

task5/task5/task5/Renderer.cpp

@@ -64,9 +64,12 @@ class MeshTriangle : public Object
         // 此刻 maxIndex = 4  numTris = 2  verts 是包含4个顶点的数组
         vertices = std::unique_ptr<Vector3f[]>(new Vector3f[maxIndex]);
         memcpy(vertices.get(), verts, sizeof(Vector3f) * maxIndex); // 相当于数组复制 verts 中的数据复制到 vertices 中
+        
         vertexIndex = std::unique_ptr<uint32_t[]>(new uint32_t[numTris * 3]);
         memcpy(vertexIndex.get(), vertsIndex, sizeof(uint32_t) * numTris * 3);
+        
         numTriangles = numTris;
+        
         stCoordinates = std::unique_ptr<Vector2f[]>(new Vector2f[maxIndex]);
         memcpy(stCoordinates.get(), st, sizeof(Vector2f) * maxIndex);
     }
@@ -100,15 +103,24 @@ class MeshTriangle : public Object
         return intersect;
     }
 
+
+    // PS : C++ 中如果参数不使用可以省略名字
+
+    // index 是当前三角形在全部三角形list 中的下标
+    // N 是三角形面的法线
     void getSurfaceProperties(const Vector3f&, const Vector3f&, const uint32_t& index, const Vector2f& uv, Vector3f& N,
                               Vector2f& st) const override
     {
+        // vertices {{-5,-3,-6}, {5,-3,-6}, {5,-3,-16}, {-5,-3,-16}};
+        // vertexIndex {0, 1, 3, 1, 2, 3};
+        // stCoordinates  {{0, 0}, {1, 0}, {1, 1}, {0, 1}};
         const Vector3f& v0 = vertices[vertexIndex[index * 3]];
         const Vector3f& v1 = vertices[vertexIndex[index * 3 + 1]];
         const Vector3f& v2 = vertices[vertexIndex[index * 3 + 2]];
         Vector3f e0 = normalize(v1 - v0);
         Vector3f e1 = normalize(v2 - v1);
         N = normalize(crossProduct(e0, e1));
+
         const Vector2f& st0 = stCoordinates[vertexIndex[index * 3]];
         const Vector2f& st1 = stCoordinates[vertexIndex[index * 3 + 1]];
         const Vector2f& st2 = stCoordinates[vertexIndex[index * 3 + 2]];

task5/task5/task5/Triangle.hpp

@@ -15,16 +15,25 @@ int main()
     sph1->materialType = DIFFUSE_AND_GLOSSY;
     sph1->diffuseColor = Vector3f(0.6, 0.7, 0.8);
 
+    // 右手坐标系
+    // 玻璃球离自己更近
     auto sph2 = std::make_unique<Sphere>(Vector3f(0.5, -0.5, -8), 1.5);
-    sph2->ior = 1.5;
+    sph2->ior = 1.5; // 折射率
     sph2->materialType = REFLECTION_AND_REFRACTION;
 
     scene.Add(std::move(sph1));
     scene.Add(std::move(sph2));
 
+    // 顶点信息
     Vector3f verts[4] = {{-5,-3,-6}, {5,-3,-6}, {5,-3,-16}, {-5,-3,-16}};
-    uint32_t vertIndex[6] = {0, 1, 3, 1, 2, 3};
+
+    // 这里描述了texture 信息  也就是texture的四个顶点
+    // 作用和 verts 相同  
     Vector2f st[4] = {{0, 0}, {1, 0}, {1, 1}, {0, 1}};
+    
+    // 所有点的下标 构成的数组 
+    // 这个数组三个一组 构成一个三角形
+    uint32_t vertIndex[6] = {0, 1, 3, 1, 2, 3};
 
     // 后面这些参数就是 MeshTriangle 构造函数所需参数
     auto mesh = std::make_unique<MeshTriangle>(verts, vertIndex, 2, st);