Call Spatial::get_global_transform and Vector3::dot only once within Camera::is_position_behind to avoid redundant work.

(cherry picked from commit b2a204799adb290cd63c9c0346574448336d8f02)

scene/3d/camera.cpp

@@ -333,8 +333,8 @@ Vector3 Camera::project_ray_origin(const Point2 &p_pos) const {
 bool Camera::is_position_behind(const Vector3 &p_pos) const {
 
 	Transform t = get_global_transform();
-	Vector3 eyedir = -get_global_transform().basis.get_axis(2).normalized();
-	return eyedir.dot(p_pos) < (eyedir.dot(t.origin) + near);
+	Vector3 eyedir = -t.basis.get_axis(2).normalized();
+	return eyedir.dot(p_pos - t.origin) < near;
 }
 
 Vector<Vector3> Camera::get_near_plane_points() const {