コード例 #1
0
        //The original algorithm calculates the intersection between two polygons, this will instead get the outside
        //Assumes the polygons are oriented counter clockwise
        //poly is the polygon we want to cut
        //Assumes the polygon we want to remove from the other polygon is convex, so clipPolygon has to be convex
        //We will end up with the !intersection of the polygons
        public static List <List <MyVector2> > ClipPolygonInverted(List <MyVector2> poly, List <Plane2> clippingPlanes)
        {
            //The result may be more than one polygons
            List <List <MyVector2> > finalPolygons = new List <List <MyVector2> >();

            List <MyVector2> vertices = new List <MyVector2>(poly);

            //The remaining polygon after each cut
            List <MyVector2> vertices_tmp = new List <MyVector2>();

            //Clip the polygon
            for (int i = 0; i < clippingPlanes.Count; i++)
            {
                Plane2 plane = clippingPlanes[i];

                //A new polygon which is the part of the polygon which is outside of this plane
                List <MyVector2> outsidePolygon = new List <MyVector2>();

                for (int j = 0; j < vertices.Count; j++)
                {
                    int jPlusOne = MathUtility.ClampListIndex(j + 1, vertices.Count);

                    MyVector2 v1 = vertices[j];
                    MyVector2 v2 = vertices[jPlusOne];

                    //Calculate the distance to the plane from each vertex
                    //This is how we will know if they are inside or outside
                    //If they are inside, the distance is positive, which is why the planes normals have to be oriented to the inside
                    float dist_to_v1 = Geometry.DistanceFromPointToPlane(plane.normal, plane.pos, v1);
                    float dist_to_v2 = Geometry.DistanceFromPointToPlane(plane.normal, plane.pos, v2);

                    //TODO: What will happen if they are exactly 0?

                    //Case 1. Both are inside (= to the left), save v2 to the other polygon
                    if (dist_to_v1 >= 0f && dist_to_v2 >= 0f)
                    {
                        vertices_tmp.Add(v2);
                    }
                    //Case 2. Both are outside (= to the right), save v1
                    else if (dist_to_v1 < 0f && dist_to_v2 < 0f)
                    {
                        outsidePolygon.Add(v2);
                    }
                    //Case 3. Outside -> Inside, save intersection point
                    else if (dist_to_v1 < 0f && dist_to_v2 >= 0f)
                    {
                        MyVector2 rayDir = MyVector2.Normalize(v2 - v1);

                        MyVector2 intersectionPoint = Intersections.GetRayPlaneIntersectionPoint(plane.pos, plane.normal, v1, rayDir);

                        outsidePolygon.Add(intersectionPoint);

                        vertices_tmp.Add(intersectionPoint);

                        vertices_tmp.Add(v2);
                    }
                    //Case 4. Inside -> Outside, save intersection point and v2
                    else if (dist_to_v1 >= 0f && dist_to_v2 < 0f)
                    {
                        MyVector2 rayDir = MyVector2.Normalize(v2 - v1);

                        MyVector2 intersectionPoint = Intersections.GetRayPlaneIntersectionPoint(plane.pos, plane.normal, v1, rayDir);

                        outsidePolygon.Add(intersectionPoint);

                        outsidePolygon.Add(v2);

                        vertices_tmp.Add(intersectionPoint);
                    }
                }

                //Add the polygon outside of this plane to the list of all polygons that are outside of all planes
                if (outsidePolygon.Count > 0)
                {
                    finalPolygons.Add(outsidePolygon);
                }

                //Add the polygon which was inside of this and previous planes to the polygon we want to test
                vertices.Clear();

                vertices.AddRange(vertices_tmp);

                vertices_tmp.Clear();
            }

            return(finalPolygons);
        }
コード例 #2
0
        //Assumes the polygons are oriented counter clockwise
        //poly is the polygon we want to cut
        //Assumes the polygon we want to remove from the other polygon is convex, so clipPolygon has to be convex
        //We will end up with the intersection of the polygons
        public static List <MyVector2> ClipPolygon(List <MyVector2> poly, List <Plane2> clippingPlanes)
        {
            //Clone the vertices because we will remove vertices from this list
            List <MyVector2> vertices = new List <MyVector2>(poly);

            //Save the new vertices temporarily in this list before transfering them to vertices
            List <MyVector2> vertices_tmp = new List <MyVector2>();

            //Clip the polygon
            for (int i = 0; i < clippingPlanes.Count; i++)
            {
                Plane2 plane = clippingPlanes[i];

                for (int j = 0; j < vertices.Count; j++)
                {
                    int jPlusOne = MathUtility.ClampListIndex(j + 1, vertices.Count);

                    MyVector2 v1 = vertices[j];
                    MyVector2 v2 = vertices[jPlusOne];

                    //Calculate the distance to the plane from each vertex
                    //This is how we will know if they are inside or outside
                    //If they are inside, the distance is positive, which is why the planes normals have to be oriented to the inside
                    float dist_to_v1 = Geometry.DistanceFromPointToPlane(plane.normal, plane.pos, v1);
                    float dist_to_v2 = Geometry.DistanceFromPointToPlane(plane.normal, plane.pos, v2);

                    //TODO: What will happen if they are exactly 0? Should maybe use a tolerance of 0.001

                    //Case 1. Both are outside (= to the right), do nothing

                    //Case 2. Both are inside (= to the left), save v2
                    if (dist_to_v1 >= 0f && dist_to_v2 >= 0f)
                    {
                        vertices_tmp.Add(v2);
                    }
                    //Case 3. Outside -> Inside, save intersection point and v2
                    else if (dist_to_v1 < 0f && dist_to_v2 >= 0f)
                    {
                        MyVector2 rayDir = MyVector2.Normalize(v2 - v1);

                        MyVector2 intersectionPoint = Intersections.GetRayPlaneIntersectionPoint(plane.pos, plane.normal, v1, rayDir);

                        vertices_tmp.Add(intersectionPoint);

                        vertices_tmp.Add(v2);
                    }
                    //Case 4. Inside -> Outside, save intersection point
                    else if (dist_to_v1 >= 0f && dist_to_v2 < 0f)
                    {
                        MyVector2 rayDir = MyVector2.Normalize(v2 - v1);

                        MyVector2 intersectionPoint = Intersections.GetRayPlaneIntersectionPoint(plane.pos, plane.normal, v1, rayDir);

                        vertices_tmp.Add(intersectionPoint);
                    }
                }

                //Add the new vertices to the list of vertices
                vertices.Clear();

                vertices.AddRange(vertices_tmp);

                vertices_tmp.Clear();
            }

            return(vertices);
        }