private Sample ComputeTree(
ref Rectangle region,
Device2D device2D,
ref Sample.Location parentTopLeft,
ref Sample.Location parentTopRight,
ref Sample.Location parentBottomLeft,
ref Sample.Location parentBottomRight,
double level = 1.0)
{
Sample sample = new Sample(ref region);
// define the points on the rectangle to test
Point topLeft = new Point(region.Left, region.Top);
Point topRight = new Point(region.Right, region.Top);
Point bottomLeft = new Point(region.Left, region.Bottom);
Point bottomRight = new Point(region.Right, region.Bottom);
// the method was not called recursively, so compute the distances to each point
if(level <= 1.0)
{
mDecomposer.Query(
ref topLeft, device2D, out sample.TopLeft.Distance, out sample.TopLeft.Intersection);
mDecomposer.Query(
ref topRight, device2D, out sample.TopRight.Distance, out sample.TopRight.Intersection);
mDecomposer.Query(
ref bottomLeft, device2D, out sample.BottomLeft.Distance, out sample.BottomLeft.Intersection);
mDecomposer.Query(
ref bottomRight, device2D, out sample.BottomRight.Distance, out sample.BottomRight.Intersection);
}
else
{
// use distances already computed by the caller
sample.TopLeft = parentTopLeft;
sample.TopRight = parentTopRight;
sample.BottomLeft = parentBottomLeft;
sample.BottomRight = parentBottomRight;
}
// do not subdivide lower than a resolved resolution unit
if(level > MaxLevel)
{
return sample;
}
int boundaryContains = 0;
Thickness thick = new Thickness(MaximumError);
Rectangle boundary = region.Expand(thick);
boundaryContains += boundary.Contains(sample.TopLeft.Intersection) ? 1 : 0;
boundaryContains += boundary.Contains(sample.TopRight.Intersection) ? 1 : 0;
boundaryContains += boundary.Contains(sample.BottomLeft.Intersection) ? 1 : 0;
boundaryContains += boundary.Contains(sample.BottomRight.Intersection) ? 1 : 0;
// compute the intersection of the region with the shape
int boundaryIntersection = 0;
boundaryIntersection += sample.TopLeft.Distance >= 0.0 ? 1 : -1;
boundaryIntersection += sample.TopRight.Distance >= 0.0 ? 1 : -1;
boundaryIntersection += sample.BottomLeft.Distance >= 0.0 ? 1 : -1;
boundaryIntersection += sample.BottomRight.Distance >= 0.0 ? 1 : -1;
double s = Math.Abs(boundaryIntersection) != 4 || boundaryContains > 0 ? 0.0 : 1.0;
double error = MinimumError + ((MaximumError - MinimumError) * s);
float halfWidth = region.Width / 2.0f;
float halfHeight = region.Height / 2.0f;
Point leftCenter = new Point(region.Left, region.Top + halfHeight);
Point topCenter = new Point(region.Left + halfWidth, region.Top);
Point rightCenter = new Point(region.Right, region.Top + halfHeight);
Point bottomCenter = new Point(region.Left + halfWidth, region.Bottom);
Point center = new Point(region.Left + halfWidth, region.Top + halfHeight);
Sample.Location centerLocation = new Sample.Location();
mDecomposer.Query(
ref center, device2D, out centerLocation.Distance, out centerLocation.Intersection);
boundaryContains += boundary.Contains(centerLocation.Intersection) ? 1 : 0;
if(boundaryContains == 0)
{
return sample;
}
Sample.Location leftCenterLocation = new Sample.Location();
Sample.Location topCenterLocation = new Sample.Location();
Sample.Location rightCenterLocation = new Sample.Location();
Sample.Location bottomCenterLocation = new Sample.Location();
mDecomposer.Query(
ref leftCenter, device2D, out leftCenterLocation.Distance, out leftCenterLocation.Intersection);
mDecomposer.Query(
ref topCenter, device2D, out topCenterLocation.Distance, out topCenterLocation.Intersection);
mDecomposer.Query(
ref rightCenter,
device2D,
out rightCenterLocation.Distance,
out rightCenterLocation.Intersection);
mDecomposer.Query(
ref bottomCenter,
device2D,
out bottomCenterLocation.Distance,
out bottomCenterLocation.Intersection);
double reconstructedLeftCenter = (sample.TopLeft.Distance + sample.BottomLeft.Distance) / 2.0;
double reconstructedTopCenter = (sample.TopLeft.Distance + sample.TopRight.Distance) / 2.0;
double reconstructedRightCenter = (sample.TopRight.Distance + sample.BottomRight.Distance) / 2.0;
double reconstructedBottomCenter = (sample.BottomLeft.Distance + sample.BottomRight.Distance) /
2.0;
double reconstructedCenter = (reconstructedTopCenter + reconstructedBottomCenter) / 2.0;
bool isLeftCenterInvalid = Math.Abs(reconstructedLeftCenter - leftCenterLocation.Distance) >
error;
bool isTopCenterInvalid = Math.Abs(reconstructedTopCenter - topCenterLocation.Distance) > error;
bool isRightCenterInvalid = Math.Abs(reconstructedRightCenter - rightCenterLocation.Distance) >
error;
bool isBottomCenterInvalid =
Math.Abs(reconstructedBottomCenter - bottomCenterLocation.Distance) > error;
bool isCenterInvalid = Math.Abs(reconstructedCenter - centerLocation.Distance) > error;
if(isLeftCenterInvalid || isTopCenterInvalid || isRightCenterInvalid || isBottomCenterInvalid ||
isCenterInvalid)
{
Rectangle topLeftRegion = new Rectangle(
topLeft.X, topLeft.Y, center.X - topLeft.X, center.Y - topLeft.Y);
sample.Children.Add(
ComputeTree(
ref topLeftRegion,
device2D,
ref sample.TopLeft,
ref topCenterLocation,
ref leftCenterLocation,
ref centerLocation,
level + 1.0));
Rectangle topRightRegion = new Rectangle(
center.X, topRight.Y, topRight.X - center.X, center.Y - topRight.Y);
sample.Children.Add(
ComputeTree(
ref topRightRegion,
device2D,
ref topCenterLocation,
ref sample.TopRight,
ref centerLocation,
ref rightCenterLocation,
level + 1.0));
Rectangle bottomRightRegion = new Rectangle(
center.X, center.Y, bottomRight.X - center.X, bottomRight.Y - center.Y);
sample.Children.Add(
ComputeTree(
ref bottomRightRegion,
device2D,
ref centerLocation,
ref rightCenterLocation,
ref bottomCenterLocation,
ref sample.BottomRight,
level + 1.0));
Rectangle bottomLeftRegion = new Rectangle(
bottomLeft.X, center.Y, center.X - bottomLeft.X, bottomLeft.Y - center.Y);
sample.Children.Add(
ComputeTree(
ref bottomLeftRegion,
device2D,
ref leftCenterLocation,
ref centerLocation,
ref sample.BottomLeft,
ref bottomCenterLocation,
level + 1.0));
}
return sample;
}
private Sample ComputeTree(ref Rectangle region, Device2D device2D)
{
Sample.Location empty = new Sample.Location();
return ComputeTree(ref region, device2D, ref empty, ref empty, ref empty, ref empty);
}