public TriangleRef(Triangle triangle) {
this(triangle, BoundingRectangle.fromPoints(triangle));
assert triangle != null;
}
private static KDNode buildTreeSAH(
TriangleRef[] refs, BoundingRectangle bounds, int depth, double lastCost) {
double minCost = Double.MAX_VALUE;
SplittingPlane minPlane = null;
SplittingPlaneAffiliation minPlaneAffiliation = null;
int minnleft = Integer.MAX_VALUE;
int minnright = Integer.MAX_VALUE;
List<TriangleEvent> events = new ArrayList<>(refs.length * 2);
for (Dimension d : Dimension.values()) {
for (TriangleRef ref : refs) {
BoundingRectangle br = bounds.intersect(ref.bounds);
if (d.getValue(br.min) == d.getValue(br.max)) {
// The triangle is planar after clipping it to the current Voxel
events.add(
new TriangleEvent(
ref.triangle, new SplittingPlane(d.getValue(br.min), d), EventType.PLANAR));
} else {
events.add(
new TriangleEvent(
ref.triangle, new SplittingPlane(d.getValue(br.min), d), EventType.START));
events.add(
new TriangleEvent(
ref.triangle, new SplittingPlane(d.getValue(br.max), d), EventType.END));
}
}
events.sort(
(a, b) -> {
int i1 = (int) Math.signum(a.p.splitValue - b.p.splitValue);
int i2 = (int) Math.signum(a.type.ord - b.type.ord);
return i1 != 0 ? i1 : i2;
}); // As per the order in the paper: Sort by splitValue, then by EventType: END < PLANAR
// < START
// Now we sweep over the event list and find the minimum cost splitting plane for this
// dimension.
int nleft = 0;
int nright = refs.length;
for (int i = 0; i < events.size(); ) {
TriangleEvent evt = events.get(i);
int pend = 0;
int pplanar = 0;
int pstart = 0;
final SplittingPlane p = evt.p;
// aggregate all p* for the same splitValue
while (evt.p.splitValue == p.splitValue) {
switch (evt.type) {
case END:
pend++;
break;
case PLANAR:
pplanar++;
break;
case START:
pstart++;
break;
}
if (++i < events.size()) {
evt = events.get(i);
} else {
break;
}
}
// Now we got all p* values for the current splitValue.
// Move plane *onto* p.
nright -= pplanar;
nright -= pend;
Tuple2<Double, SplittingPlaneAffiliation> result =
surfaceAreaHeuristic(bounds, p, nleft, nright, pplanar);
if (result.v1 < minCost) {
minCost = result.v1;
minPlane = p;
minPlaneAffiliation = result.v2;
minnleft = nleft;
minnright = nright;
switch (minPlaneAffiliation) {
case LEFT:
minnleft += pplanar;
break;
case RIGHT:
minnright += pplanar;
break;
}
}
// Move plane *beyond* p
nleft += pstart;
nleft += pplanar;
assert nleft + nright >= refs.length;
assert minnleft + minnright >= refs.length;
}
events.clear();
}
if (INTERSECTION_COST * refs.length < minCost || depth > 30 || lastCost <= minCost) {
return KDNode.leaf(bounds, refs);
}
assert refs.length > 1;
// We found the best splitting plane and the associated costs, all that is left to do is split.
TriangleRef[] left = new TriangleRef[minnleft];
TriangleRef[] right = new TriangleRef[minnright];
int l = 0;
int r = 0;
BoundingRectangle lv = BoundingRectangle.EMPTY;
BoundingRectangle rv = BoundingRectangle.EMPTY;
for (TriangleRef ref : refs) {
if (minPlane.dimension.getValue(ref.bounds.min) == minPlane.splitValue
&& minPlane.dimension.getValue(ref.bounds.max) == minPlane.splitValue) {
if (minPlaneAffiliation == SplittingPlaneAffiliation.RIGHT) {
right[r++] = ref;
rv = rv.merge(ref.bounds);
} else {
left[l++] = ref;
lv = lv.merge(ref.bounds);
}
} else {
if (minPlane.dimension.getValue(ref.bounds.min) < minPlane.splitValue) {
left[l++] = ref;
lv = lv.merge(ref.bounds);
}
if (minPlane.dimension.getValue(ref.bounds.max) > minPlane.splitValue) {
right[r++] = ref;
rv = rv.merge(ref.bounds);
}
// In the remaining case where min == max == splitValue, the triangle
// is planar (extent == 0) and will we dealt with in the other if branch
// according to minPlaneAffiliation.
}
}
lv =
splitBoundingRect(lv.intersect(bounds), minPlane)
.v1; // I hope this is accurate enough. don't want clip all triangles
rv = splitBoundingRect(rv.intersect(bounds), minPlane).v2;
assert l == left.length;
assert r == right.length;
KDNode leftChild = buildTreeSAH(left, lv, depth + 1, minCost);
KDNode rightChild = buildTreeSAH(right, rv, depth + 1, minCost);
return KDNode.inner(bounds, leftChild, rightChild, minPlane);
}
private static double surfaceArea(BoundingRectangle v) {
Point2D e = v.extent();
return 2 * (e.getX() + e.getY());
}
