private static void add(float3 p, float3[] dest, ref int pcount)
{
dest[pcount++] = new float3(p);
Debug.Assert(pcount <= 4);
}
public static PlaneTriResult planeTriIntersection(float4 plane, FaceTri triangle, float epsilon, ref float3[] front, out int fcount, ref float3[] back, out int bcount)
{
fcount = 0;
bcount = 0;
// get the three vertices of the triangle.
float3 p1 = triangle.P1;
float3 p2 = triangle.P2;
float3 p3 = triangle.P3;
PlaneTriResult r1 = getSidePlane(p1, plane, epsilon); // compute the side of the plane each vertex is on
PlaneTriResult r2 = getSidePlane(p2, plane, epsilon);
PlaneTriResult r3 = getSidePlane(p3, plane, epsilon);
if (r1 == r2 && r1 == r3) // if all three vertices are on the same side of the plane.
{
if (r1 == PlaneTriResult.PTR_FRONT) // if all three are in front of the plane, then copy to the 'front' output triangle.
{
add(p1, front, ref fcount);
add(p2, front, ref fcount);
add(p3, front, ref fcount);
}
else
{
add(p1, back, ref bcount); // if all three are in 'back' then copy to the 'back' output triangle.
add(p2, back, ref bcount);
add(p3, back, ref bcount);
}
return(r1); // if all three points are on the same side of the plane return result
}
// ok.. we need to split the triangle at the plane.
// First test ray segment P1 to P2
if (r1 == r2) // if these are both on the same side...
{
if (r1 == PlaneTriResult.PTR_FRONT)
{
add(p1, front, ref fcount);
add(p2, front, ref fcount);
}
else
{
add(p1, back, ref bcount);
add(p2, back, ref bcount);
}
}
else
{
float3 split = new float3();
intersect(p1, p2, split, plane);
if (r1 == PlaneTriResult.PTR_FRONT)
{
add(p1, front, ref fcount);
add(split, front, ref fcount);
add(split, back, ref bcount);
add(p2, back, ref bcount);
}
else
{
add(p1, back, ref bcount);
add(split, back, ref bcount);
add(split, front, ref fcount);
add(p2, front, ref fcount);
}
}
// Next test ray segment P2 to P3
if (r2 == r3) // if these are both on the same side...
{
if (r3 == PlaneTriResult.PTR_FRONT)
{
add(p3, front, ref fcount);
}
else
{
add(p3, back, ref bcount);
}
}
else
{
float3 split = new float3(); // split the point
intersect(p2, p3, split, plane);
if (r3 == PlaneTriResult.PTR_FRONT)
{
add(split, front, ref fcount);
add(split, back, ref bcount);
add(p3, front, ref fcount);
}
else
{
add(split, front, ref fcount);
add(split, back, ref bcount);
add(p3, back, ref bcount);
}
}
// Next test ray segment P3 to P1
if (r3 != r1) // if these are both on the same side...
{
float3 split = new float3(); // split the point
intersect(p3, p1, split, plane);
if (r1 == PlaneTriResult.PTR_FRONT)
{
add(split, front, ref fcount);
add(split, back, ref bcount);
}
else
{
add(split, front, ref fcount);
add(split, back, ref bcount);
}
}
return(PlaneTriResult.PTR_SPLIT);
}
private static float DistToPt(float3 p, float4 plane)
{
return(p.x * plane.x + p.y * plane.y + p.z * plane.z + plane.w);
}