// Intersects a mesh with a brush (set of planes)
#region Intersect
public void Intersect(AABB cuttingNodeBounds,
Plane[] cuttingNodePlanes,
Vector3 cuttingNodeTranslation,
Vector3 inputPolygonTranslation,
List <Polygon> inputPolygons,
List <Polygon> inside,
List <Polygon> aligned,
List <Polygon> revAligned,
List <Polygon> outside)
{
var categories = new PolygonSplitResult[cuttingNodePlanes.Length];
var translatedPlanes = new Plane[cuttingNodePlanes.Length];
var translation = Vector3.Subtract(cuttingNodeTranslation, inputPolygonTranslation);
// translate the planes we cut our polygons with so that they're located at the same
// relative distance from the polygons as the brushes are from each other.
for (int i = 0; i < cuttingNodePlanes.Length; i++)
{
translatedPlanes[i] = Plane.Translated(cuttingNodePlanes[i], translation);
}
var vertices = this.Vertices;
var edges = this.Edges;
var planes = this.Planes;
for (int i = inputPolygons.Count - 1; i >= 0; i--)
{
var inputPolygon = inputPolygons[i];
if (inputPolygon.FirstIndex == -1)
{
continue;
}
var bounds = inputPolygon.Bounds;
var finalResult = PolygonSplitResult.CompletelyInside;
// A quick check if the polygon lies outside the planes we're cutting our polygons with.
if (!AABB.IsOutside(cuttingNodeBounds, translation, bounds))
{
PolygonSplitResult intermediateResult;
Polygon outsidePolygon = null;
for (int otherIndex = 0; otherIndex < translatedPlanes.Length; otherIndex++)
{
var translatedCuttingPlane = translatedPlanes[otherIndex];
var side = cuttingNodePlanes[otherIndex].OnSide(bounds, translation.Negated());
if (side == PlaneSideResult.Outside)
{
finalResult = PolygonSplitResult.CompletelyOutside;
break; // nothing left to process, so we exit
}
else
if (side == PlaneSideResult.Inside)
{
continue;
}
var polygon = inputPolygon;
intermediateResult = PolygonSplit(translatedCuttingPlane, inputPolygonTranslation, ref polygon, out outsidePolygon);
inputPolygon = polygon;
if (intermediateResult == PolygonSplitResult.CompletelyOutside)
{
finalResult = PolygonSplitResult.CompletelyOutside;
break; // nothing left to process, so we exit
}
else
if (intermediateResult == PolygonSplitResult.Split)
{
if (outside != null)
{
outside.Add(outsidePolygon);
}
// Note: left over is still completely inside,
// or plane (opposite) aligned
}
else
if (intermediateResult != PolygonSplitResult.CompletelyInside)
{
finalResult = intermediateResult;
}
}
}
else
{
finalResult = PolygonSplitResult.CompletelyOutside;
}
switch (finalResult)
{
case PolygonSplitResult.CompletelyInside: inside.Add(inputPolygon); break;
case PolygonSplitResult.CompletelyOutside: outside.Add(inputPolygon); break;
// The polygon can only be visible if it's part of the last brush that shares it's surface area,
// otherwise we'd get overlapping polygons if two brushes overlap.
// When the (final) polygon is aligned with one of the cutting planes, we know it lies on the surface of
// the CSG node we're cutting the polygons with. We also know that this node is not the node this polygon belongs to
// because we've done that check earlier on. So we flag this polygon as being invisible.
case PolygonSplitResult.PlaneAligned: inputPolygon.Visible = false; aligned.Add(inputPolygon); break;
case PolygonSplitResult.PlaneOppositeAligned: inputPolygon.Visible = false; revAligned.Add(inputPolygon); break;
}
}
}
// Categorize the given inputPolygons as being inside/outside or (reverse-)aligned
// with the shape that is defined by the current brush or csg-branch.
// When an inputPolygon crosses the node, it is split into pieces and every individual
// piece is then categorized.
#region Categorize
public static void Categorize(CSGNode processedNode,
CSGMesh processedMesh,
CSGNode categorizationNode,
List <Polygon> inputPolygons,
List <Polygon> inside,
List <Polygon> aligned,
List <Polygon> revAligned,
List <Polygon> outside)
{
// When you go deep enough in the tree it's possible that all categories point to the same
// destination. So we detect that and potentially avoid a lot of wasted work.
if (inside == revAligned &&
inside == aligned &&
inside == outside)
{
inside.AddRange(inputPolygons);
return;
}
Restart:
if (processedNode == categorizationNode)
{
// When the currently processed node is the same node as we categorize against, then
// we know that all our polygons are visible and we set their default category
// (usually aligned, unless it's an instancing node in which case it's precalculated)
foreach (var polygon in inputPolygons)
{
switch (polygon.Category)
{
case PolygonCategory.Aligned: aligned.Add(polygon); break;
case PolygonCategory.ReverseAligned: revAligned.Add(polygon); break;
case PolygonCategory.Inside: inside.Add(polygon); break;
case PolygonCategory.Outside: outside.Add(polygon); break;
}
// When brushes overlap and they share the same surface area we only want to keep
// the polygons of the last brush in the tree, and skip all others.
// At this point in the tree we know that this polygon belongs to this brush, so
// we set it to visible. If the polygon is found to share the surface area with another
// brush further on in the tree it'll be set to invisible again in mesh.Intersect.
polygon.Visible = true;
}
return;
}
var leftNode = categorizationNode.Left;
var rightNode = categorizationNode.Right;
switch (categorizationNode.NodeType)
{
case CSGNodeType.Brush:
{
processedMesh.Intersect(categorizationNode.Bounds,
categorizationNode.Generator.GetPlanes(categorizationNode.WorldTransformation),
categorizationNode.Translation,
processedNode.Translation,
inputPolygons,
inside, aligned, revAligned, outside);
break;
}
case CSGNodeType.Addition:
{
// ( A || B)
var relativeLeftTrans = Vector3.Subtract(processedNode.Translation, leftNode.Translation);
var relativeRightTrans = Vector3.Subtract(processedNode.Translation, rightNode.Translation);
if (AABB.IsOutside(processedNode.Bounds, relativeLeftTrans, leftNode.Bounds))
{
if (AABB.IsOutside(processedNode.Bounds, relativeRightTrans, rightNode.Bounds))
{
// When our polygons lie outside the bounds of both the left and the right node, then
// all the polygons can be categorized as being 'outside'
outside.AddRange(inputPolygons);
}
else
{
//Categorize(processedNode, mesh, right,
// inputPolygons,
// inside, aligned, revAligned, outside);
categorizationNode = rightNode;
goto Restart;
}
}
else
if (AABB.IsOutside(processedNode.Bounds, relativeRightTrans, rightNode.Bounds))
{
//Categorize(processedNode, left, mesh,
// inputPolygons,
// inside, aligned, revAligned, outside);
categorizationNode = leftNode;
goto Restart;
}
else
{
LogicalOr(processedNode, processedMesh, categorizationNode,
inputPolygons,
inside, aligned, revAligned, outside,
false, false);
}
break;
}
case CSGNodeType.Common:
{
// !(!A || !B)
var relativeLeftTrans = Vector3.Subtract(processedNode.Translation, leftNode.Translation);
var relativeRightTrans = Vector3.Subtract(processedNode.Translation, rightNode.Translation);
if (AABB.IsOutside(processedNode.Bounds, relativeLeftTrans, leftNode.Bounds) ||
AABB.IsOutside(processedNode.Bounds, relativeRightTrans, rightNode.Bounds))
{
// When our polygons lie outside the bounds of both the left and the right node, then
// all the polygons can be categorized as being 'outside'
outside.AddRange(inputPolygons);
}
else
{
LogicalOr(processedNode, processedMesh, categorizationNode,
inputPolygons,
outside, revAligned, aligned, inside,
true, true);
}
break;
}
case CSGNodeType.Subtraction:
{
// !(!A || B)
var relativeLeftTrans = Vector3.Subtract(processedNode.Translation, leftNode.Translation);
var relativeRightTrans = Vector3.Subtract(processedNode.Translation, rightNode.Translation);
if (AABB.IsOutside(processedNode.Bounds, relativeLeftTrans, leftNode.Bounds))
{
// When our polygons lie outside the bounds of both the left node, then
// all the polygons can be categorized as being 'outside'
outside.AddRange(inputPolygons);
}
else
if (AABB.IsOutside(processedNode.Bounds, relativeRightTrans, rightNode.Bounds))
{
categorizationNode = leftNode;
goto Restart;
}
else
{
LogicalOr(processedNode, processedMesh, categorizationNode,
inputPolygons,
outside, revAligned, aligned, inside,
true, false);
}
break;
}
}
}