public static unsafe void GetFaceSidePlanes(ref NativeBuffer <ClipPlane> output, NativePlane facePlane, int faceIndex, RigidTransform transform, NativeHull hull)
{
NativeHalfEdge *start = hull.GetEdgePtr(hull.GetFacePtr(faceIndex)->Edge);
NativeHalfEdge *current = start;
do
{
NativeHalfEdge *twin = hull.GetEdgePtr(current->Twin);
float3 P = math.transform(transform, hull.GetVertex(current->Origin));
float3 Q = math.transform(transform, hull.GetVertex(twin->Origin));
ClipPlane clipPlane = default;
clipPlane.edgeId = twin->Twin; //edge ID.
clipPlane.plane.Normal = math.normalize(math.cross(Q - P, facePlane.Normal));
clipPlane.plane.Offset = math.dot(clipPlane.plane.Normal, P);
output.Add(clipPlane);
current = hull.GetEdgePtr(current->Next);
}while (current != start);
}
/// <summary>
/// Perform the Sutherland-Hodgman polygon clipping. Since all side planes are pointing outwards the points that are *behind* the plane are kept.
/// </summary>
public static void Clip(ClipPlane clipPlane, ref NativeBuffer <ClipVertex> input, ref NativeBuffer <ClipVertex> output)
{
//Debug.Assert(output.IsCreated && output.Length == 0);
Debug.Assert(input.IsCreated && input.Length != 0);
ClipVertex vertex1 = input[input.Length - 1];
float distance1 = clipPlane.plane.Distance(vertex1.position);
for (int i = 0; i < input.Length; ++i)
{
ClipVertex vertex2 = input[i];
float distance2 = clipPlane.plane.Distance(vertex2.position);
if (distance1 <= 0 && distance2 <= 0)
{
// Both vertices are behind or lying on the plane -> keep vertex2
output.Add(vertex2);
}
else if (distance1 <= 0 && distance2 > 0)
{
// vertex1 is behind the plane, vertex2 is in front -> intersection point
float fraction = distance1 / (distance1 - distance2);
float3 position = vertex1.position + fraction * (vertex2.position - vertex1.position);
// Keep intersection point
ClipVertex vertex;
vertex.position = position;
vertex.featurePair.InEdge1 = -1;
vertex.featurePair.InEdge2 = vertex1.featurePair.OutEdge2;
vertex.featurePair.OutEdge1 = (sbyte)clipPlane.edgeId;
vertex.featurePair.OutEdge2 = -1;
vertex.plane = clipPlane.plane;
vertex.hull2local = position;
output.Add(vertex);
}
else if (distance2 <= 0 && distance1 > 0)
{
// vertex2 is behind of the plane, vertex1 is in front -> intersection point
float fraction = distance1 / (distance1 - distance2);
float3 position = vertex1.position + fraction * (vertex2.position - vertex1.position);
// Keep intersection point
ClipVertex vertex;
vertex.position = position;
vertex.featurePair.InEdge1 = (sbyte)clipPlane.edgeId;
vertex.featurePair.OutEdge1 = -1;
vertex.featurePair.InEdge2 = -1;
vertex.featurePair.OutEdge2 = vertex1.featurePair.OutEdge2;
vertex.plane = clipPlane.plane;
vertex.hull2local = position;
output.Add(vertex);
// Keep vertex2 as well
output.Add(vertex2);
}
// Keep vertex2 as starting vertex for next edge
vertex1 = vertex2;
distance1 = distance2;
}
}