half plane

algoim/organizer/primitive.hpp

@@ -632,6 +632,32 @@ public:
     void print() override { std::cout << "Cone Description" << std::endl; }
 };
 
+class HalfPlaneDesc : virtual public PrimitiveDesc
+{
+public:
+    // 基点，法向
+    uvector3 basePt, normal;
+
+    HalfPlaneDesc(const uvector3& basePt_, const uvector3& normal_) : PrimitiveDesc(), basePt(basePt_), normal(normal_) {}
+
+    // 所有点应该位于一个面
+    // 点顺序满足：叉乘指向法向，如 A B C D4点，ABxBC 与 BCxCD 与 normal同向
+    HalfPlaneDesc(const std::vector<uvector3>& vertices)
+    {
+        assert(vertices.size() >= 3);
+        uvector3 V01  = vertices[1] - vertices[0];
+        uvector3 v02  = vertices[2] - vertices[0];
+        normal        = cross(V01, v02);
+        normal       /= norm(normal);
+        real d        = -dot(normal, vertices[0]);
+        basePt        = vertices[0];
+        // test other vertices
+        for (int i = 3; i < vertices.size(); ++i) {
+            assert(dot(normal, vertices[i]) + d < std::numeric_limits<real>::epsilon());
+        }
+    }
+};
+
 class MeshDesc : virtual public PrimitiveDesc
 {
 public:
@@ -714,6 +740,21 @@ struct Scene {
     AABB                             boundary;
 };
 
+void makeHalfPlane(const HalfPlaneDesc& halfPlaneDesc, VisiblePrimitiveRep& visiblePrimitive)
+{
+    assert(visiblePrimitive.tensors.size() == 1);
+    auto& tensor = visiblePrimitive.tensors[0];
+    assert(all(tensor.ext() == 3));
+    xarrayInit(tensor);
+    tensor.m(uvector3(0, 0, 0)) = -dot(halfPlaneDesc.normal, halfPlaneDesc.basePt);
+    tensor.m(uvector3(1, 0, 0)) = halfPlaneDesc.normal(0);
+    tensor.m(uvector3(0, 1, 0)) = halfPlaneDesc.normal(1);
+    tensor.m(uvector3(0, 0, 1)) = halfPlaneDesc.normal(2);
+
+    // AABB
+    visiblePrimitive.aabb.extend(halfPlaneDesc.basePt);
+}
+
 void makeMesh(const MeshDesc& mesh, VisiblePrimitiveRep& visiblePrimitive)
 {
     assert(visiblePrimitive.tensors.size() == mesh.indexInclusiveScan.size());