Ignore backfaces during Node3D selection

Author: vaner-org

core/math/triangle_mesh.cpp

@@ -290,7 +290,7 @@ bool TriangleMesh::intersect_segment(const Vector3 &p_begin, const Vector3 &p_en
 	return inters;
 }
 
-bool TriangleMesh::intersect_ray(const Vector3 &p_begin, const Vector3 &p_dir, Vector3 &r_point, Vector3 &r_normal, int32_t *r_surf_index, int32_t *r_face_index) const {
+bool TriangleMesh::intersect_ray(const Vector3 &p_begin, const Vector3 &p_dir, Vector3 &r_point, Vector3 &r_normal, int32_t *r_surf_index, int32_t *r_face_index, bool p_ignore_backfaces) const {
 	if (!valid) {
 		return false;
 	}
@@ -338,18 +338,23 @@ bool TriangleMesh::intersect_ray(const Vector3 &p_begin, const Vector3 &p_dir, V
 						Vector3 res;
 
 						if (f3.intersects_ray(p_begin, p_dir, &res)) {
-							real_t nd = n.dot(res);
-							if (nd < d) {
-								d = nd;
-								r_point = res;
-								r_normal = f3.get_plane().get_normal();
-								if (r_surf_index) {
-									*r_surf_index = s.surface_index;
+							Vector3 face_normal = f3.get_plane().get_normal();
+							if (p_ignore_backfaces && p_dir.dot(face_normal) >= 0) {
+								// Skip this triangle.
+							} else {
+								real_t nd = n.dot(res);
+								if (nd < d) {
+									d = nd;
+									r_point = res;
+									r_normal = face_normal;
+									if (r_surf_index) {
+										*r_surf_index = s.surface_index;
+									}
+									if (r_face_index) {
+										*r_face_index = b.face_index;
+									}
+									inters = true;
 								}
-								if (r_face_index) {
-									*r_face_index = b.face_index;
-								}
-								inters = true;
 							}
 						}
 

core/math/triangle_mesh.h

@@ -85,7 +85,7 @@ class TriangleMesh : public RefCounted {
 public:
 	bool is_valid() const;
 	bool intersect_segment(const Vector3 &p_begin, const Vector3 &p_end, Vector3 &r_point, Vector3 &r_normal, int32_t *r_surf_index = nullptr, int32_t *r_face_index = nullptr) const;
-	bool intersect_ray(const Vector3 &p_begin, const Vector3 &p_dir, Vector3 &r_point, Vector3 &r_normal, int32_t *r_surf_index = nullptr, int32_t *r_face_index = nullptr) const;
+	bool intersect_ray(const Vector3 &p_begin, const Vector3 &p_dir, Vector3 &r_point, Vector3 &r_normal, int32_t *r_surf_index = nullptr, int32_t *r_face_index = nullptr, bool p_ignore_backfaces = false) const;
 	bool inside_convex_shape(const Plane *p_planes, int p_plane_count, const Vector3 *p_points, int p_point_count, Vector3 p_scale = Vector3(1, 1, 1)) const;
 	Vector<Face3> get_faces() const;
 

editor/scene/3d/node_3d_editor_gizmos.cpp

@@ -764,7 +764,7 @@ bool EditorNode3DGizmo::intersect_ray(Camera3D *p_camera, const Point2 &p_point,
 
 		for (Ref<TriangleMesh> collision_mesh : collision_meshes) {
 			if (collision_mesh.is_valid()) {
-				if (collision_mesh->intersect_ray(ray_from, ray_dir, rpos, rnorm)) {
+				if (collision_mesh->intersect_ray(ray_from, ray_dir, rpos, rnorm, nullptr, nullptr, true)) {
 					r_pos = gt.xform(rpos);
 					r_normal = gt.basis.xform(rnorm).normalized();
 					return true;

scene/debugger/scene_debugger.cpp

@@ -2562,7 +2562,7 @@ void RuntimeNodeSelect::_find_3d_items_at_pos(const Point2 &p_pos, Vector<Select
 				Transform3D gt = geo_instance->get_global_transform();
 				Transform3D ai = gt.affine_inverse();
 				Vector3 point, normal;
-				if (mesh_collision->intersect_ray(ai.xform(pos), ai.basis.xform(ray).normalized(), point, normal)) {
+				if (mesh_collision->intersect_ray(ai.xform(pos), ai.basis.xform(ray).normalized(), point, normal, nullptr, nullptr, true)) {
 					SelectResult res;
 					res.item = Object::cast_to<Node>(obj);
 					res.order = -pos.distance_to(gt.xform(point));