private static TriIntersections CalculateIntersections(Vector3[] meshVertices, int[] meshTriangles, Vector3[] meshNormals,
int triStartIndex,
Vector3 cutStartObjectSpace,
Vector3 cutNormal, bool log)
{
var result = new TriIntersections();
var indexA = meshTriangles[triStartIndex];
var indexB = meshTriangles[triStartIndex + 1];
var indexC = meshTriangles[triStartIndex + 2];
var pointA = meshVertices[indexA];
var pointB = meshVertices[indexB];
var pointC = meshVertices[indexC];
// It doesn't really matter where the origin is, the point is that
// it's a point on the plane. I think. So this could be an optimization.
var cutPlaneOrigin = cutStartObjectSpace;
var intersectsAB = TryIntersect(pointA, pointB, cutPlaneOrigin, cutNormal, log, ref result.Iab);
var intersectsBC = TryIntersect(pointB, pointC, cutPlaneOrigin, cutNormal, log, ref result.Ibc);
var intersectsCA = TryIntersect(pointC, pointA, cutPlaneOrigin, cutNormal, log, ref result.Ica);
var intersectCount = 0;
if (intersectsAB)
{
intersectCount++;
}
if (intersectsBC)
{
intersectCount++;
}
if (intersectsCA)
{
intersectCount++;
}
if (intersectCount == 2)
{
if (intersectsAB && intersectsBC)
{
result.type = CutType.ABBC;
}
else if (intersectsAB && intersectsCA)
{
result.type = CutType.ABCA;
}
else
{
result.type = CutType.BCCA;
}
result.A = pointA;
result.B = pointB;
result.C = pointC;
result.normalA = meshNormals[indexA];
result.normalB = meshNormals[indexB];
result.normalC = meshNormals[indexC];
//TODO: actually weigh-blend the normals depending on where the cut is
result.normalIAB = (result.normalA + result.normalB) / 2f;
result.normalIBC = (result.normalB + result.normalC) / 2f;
result.normalICA = (result.normalC + result.normalA) / 2f;
}
return(result);
}
private static void CutTriangleAndCopyVertsAndNormals(Mesh mesh, TriIntersections cut,
Vector3 cutStartPos, Vector3 cutNormal,
List <Vector3> vertsAbove, List <Vector3> normsAbove,
List <Vector3> vertsBelow, List <Vector3> normsBelow,
List <Edge> cutSurfaceEdges, bool log)
{
switch (cut.type)
{
case CutType.ABCA:
{
var isSmallPieceAboveCut = Vector3.Dot(cutNormal, cut.A - cutStartPos) > 0f;
List <Vector3> smallPieceVerts = isSmallPieceAboveCut ? vertsAbove : vertsBelow;
List <Vector3> smallPieceNorms = isSmallPieceAboveCut ? normsAbove : normsBelow;
List <Vector3> bigPieceVerts = isSmallPieceAboveCut ? vertsBelow : vertsAbove;
List <Vector3> bigPieceNorms = isSmallPieceAboveCut ? normsBelow : normsAbove;
smallPieceVerts.Add(cut.A); smallPieceVerts.Add(cut.Iab); smallPieceVerts.Add(cut.Ica);
smallPieceNorms.Add(cut.normalA);
smallPieceNorms.Add(cut.normalIAB);
smallPieceNorms.Add(cut.normalICA);
bigPieceVerts.Add(cut.C); bigPieceVerts.Add(cut.Ica); bigPieceVerts.Add(cut.Iab);
bigPieceVerts.Add(cut.C); bigPieceVerts.Add(cut.Iab); bigPieceVerts.Add(cut.B);
bigPieceNorms.Add(cut.normalC);
bigPieceNorms.Add(cut.normalICA);
bigPieceNorms.Add(cut.normalIAB);
bigPieceNorms.Add(cut.normalC);
bigPieceNorms.Add(cut.normalIAB);
bigPieceNorms.Add(cut.normalB);
if (!isSmallPieceAboveCut)
{
cutSurfaceEdges.Add(new Edge(cut.Iab, cut.Ica));
}
else
{
cutSurfaceEdges.Add(new Edge(cut.Ica, cut.Iab));
}
break;
}
case CutType.ABBC:
{
var isSmallPieceAboveCut = Vector3.Dot(cutNormal, cut.B - cutStartPos) > 0f;
List <Vector3> smallPieceVerts = isSmallPieceAboveCut ? vertsAbove : vertsBelow;
List <Vector3> smallPieceNorms = isSmallPieceAboveCut ? normsAbove : normsBelow;
List <Vector3> bigPieceVerts = isSmallPieceAboveCut ? vertsBelow : vertsAbove;
List <Vector3> bigPieceNorms = isSmallPieceAboveCut ? normsBelow : normsAbove;
smallPieceVerts.Add(cut.B); smallPieceVerts.Add(cut.Ibc); smallPieceVerts.Add(cut.Iab);
smallPieceNorms.Add(cut.normalB);
smallPieceNorms.Add(cut.normalIBC);
smallPieceNorms.Add(cut.normalIAB);
bigPieceVerts.Add(cut.A); bigPieceVerts.Add(cut.Iab); bigPieceVerts.Add(cut.Ibc);
bigPieceVerts.Add(cut.A); bigPieceVerts.Add(cut.Ibc); bigPieceVerts.Add(cut.C);
bigPieceNorms.Add(cut.normalA);
bigPieceNorms.Add(cut.normalIAB);
bigPieceNorms.Add(cut.normalIBC);
bigPieceNorms.Add(cut.normalA);
bigPieceNorms.Add(cut.normalIBC);
bigPieceNorms.Add(cut.normalC);
if (!isSmallPieceAboveCut)
{
cutSurfaceEdges.Add(new Edge(cut.Ibc, cut.Iab));
}
else
{
cutSurfaceEdges.Add(new Edge(cut.Iab, cut.Ibc));
}
break;
}
case CutType.BCCA:
{
var isSmallPieceAboveCut = Vector3.Dot(cutNormal, cut.C - cutStartPos) > 0f;
List <Vector3> smallPieceVerts = isSmallPieceAboveCut ? vertsAbove : vertsBelow;
List <Vector3> smallPieceNorms = isSmallPieceAboveCut ? normsAbove : normsBelow;
List <Vector3> bigPieceVerts = isSmallPieceAboveCut ? vertsBelow : vertsAbove;
List <Vector3> bigPieceNorms = isSmallPieceAboveCut ? normsBelow : normsAbove;
smallPieceVerts.Add(cut.C); smallPieceVerts.Add(cut.Ica); smallPieceVerts.Add(cut.Ibc);
smallPieceNorms.Add(cut.normalC);
smallPieceNorms.Add(cut.normalICA);
smallPieceNorms.Add(cut.normalIBC);
bigPieceVerts.Add(cut.B); bigPieceVerts.Add(cut.Ibc); bigPieceVerts.Add(cut.Ica);
bigPieceVerts.Add(cut.B); bigPieceVerts.Add(cut.Ica); bigPieceVerts.Add(cut.A);
bigPieceNorms.Add(cut.normalB);
bigPieceNorms.Add(cut.normalIBC);
bigPieceNorms.Add(cut.normalICA);
bigPieceNorms.Add(cut.normalB);
bigPieceNorms.Add(cut.normalICA);
bigPieceNorms.Add(cut.normalA);
if (!isSmallPieceAboveCut)
{
cutSurfaceEdges.Add(new Edge(cut.Ica, cut.Ibc));
}
else
{
cutSurfaceEdges.Add(new Edge(cut.Ibc, cut.Ica));
}
break;
}
default:
break;
}
}