private static void RasterizeBetweenLines(
float yStart, float yEnd,
Vector2 Line0Start, Vector2 Line0End,
Vector2 Line1Start, Vector2 Line1End, ScanareaDelegate scanarea)
{
float Line0StepX = (Line0End.X - Line0Start.X) / (Line0End.Y - Line0Start.Y);
float Line1StepX = (Line1End.X - Line1Start.X) / (Line1End.Y - Line1Start.Y);
float Line0BaseX = Line0Start.X - Line0StepX * Line0Start.Y;
float Line1BaseX = Line1Start.X - Line1StepX * Line1Start.Y;
if (IsFinite(Line0StepX))
{
if (IsFinite(Line1StepX))
{ // Both lines are defined
int yStartInt = (int)Math.Floor(yStart);
int yEndInt = (int)Math.Ceiling(yEnd);
for (int y = yStartInt; y < yEndInt; ++y)
{
float thisY = Math.Min(yEnd, Math.Max(yStart, y));
float thisLine0 = Line0BaseX + thisY * Line0StepX;
float thisLine1 = Line1BaseX + thisY * Line1StepX;
float nextY = Math.Min(yEnd, Math.Max(yStart, y + 1));
float nextLine0 = Line0BaseX + nextY * Line0StepX;
float nextLine1 = Line1BaseX + nextY * Line1StepX;
float fromX = Math.Min(Math.Min(thisLine0, nextLine0), Math.Min(thisLine1, nextLine1));
float toX = Math.Max(Math.Max(thisLine0, nextLine0), Math.Max(thisLine1, nextLine1));
scanarea((int)Math.Floor(fromX), y, (int)Math.Ceiling(toX), y + 1);
}
}
else
{ // Line 1 has undefiend slope
float y = (Line1Start.Y + Line1End.Y) * 0.5f;
float line0x = Line0BaseX + y * Line0StepX;
float fromX = Math.Min(line0x, Math.Min(Line1Start.X, Line1End.X));
float toX = Math.Max(line0x, Math.Max(Line1Start.X, Line1End.X));
int yInt = (int)Math.Floor(y);
scanarea((int)Math.Floor(fromX), yInt, (int)Math.Ceiling(toX), yInt + 1);
}
}
else
{
if (IsFinite(Line1StepX))
{ // Line 0 has undefined slope
float y = (Line0Start.Y + Line0End.Y) * 0.5f;
float line1x = Line1BaseX + y * Line1StepX;
float fromX = Math.Min(line1x, Math.Min(Line0Start.X, Line0End.X));
float toX = Math.Max(line1x, Math.Max(Line0Start.X, Line0End.X));
int yInt = (int)Math.Floor(y);
scanarea((int)Math.Floor(fromX), yInt, (int)Math.Ceiling(toX), yInt + 1);
}
else
{ // Line 0 and 1 have undefined slope
}
}
}
public static void RasterizeTriangle(Vector2 p0, Vector2 p1, Vector2 p2, ScanareaDelegate scanarea)
{
// Sort to ensure vertical point order:
// p0 (Minimum Y)
// p1
// p2 (Maximum Y)
if (p0.Y > p1.Y)
{
Swap(ref p0, ref p1);
}
if (p1.Y > p2.Y)
{
Swap(ref p1, ref p2);
}
if (p0.Y > p1.Y)
{
Swap(ref p0, ref p1);
}
RasterizeBetweenLines(p0.Y, p1.Y, p0, p1, p0, p2, scanarea);
RasterizeBetweenLines(p1.Y, p2.Y, p1, p2, p0, p2, scanarea);
}
public static void RasterizeQuadUniquely(Vector2 p0, Vector2 p1, Vector2 p2, Vector2 p3, ScanareaDelegate scanarea)
{
// Performance could be improved by using an algorithm that ensures unique invokation automatically
// and does not call 'scanarea' for each and every point seperately
var result = new HashSet <Tuple <int, int> >();
RasterizeQuad(p0, p1, p2, p3,
(startX, startY, endX, endY) =>
{
for (int y = startY; y < endY; ++y)
{
for (int x = startX; x < endX; ++x)
{
result.Add(new Tuple <int, int>(x, y));
}
}
});
foreach (var coordinate in result)
{
scanarea.Invoke(coordinate.Item1, coordinate.Item2, coordinate.Item1 + 1, coordinate.Item2 + 1);
}
}
public static void RasterizeQuad(Vector2 p0, Vector2 p1, Vector2 p2, Vector2 p3, ScanareaDelegate scanarea)
{
RasterizeTriangle(p0, p1, p2, scanarea);
RasterizeTriangle(p0, p2, p3, scanarea);
}