Che ne dici di mantenere un intervallo di colonne per ogni riga che si trova nel triangolo? Quello che puoi fare è impostare la colonna min e max per ogni riga in cui si trova ogni punto e dove ogni linea di triangolo attraversa una linea di separazione di riga orizzontale.
public class Point
{
public float X;
public float Y;
public Point(float x, float y) { this.X = x; this.Y = y; }
}
public class Line
{
float ROW_SIZE = 100f;
float COL_SIZE = 100f;
public Point P1, P2; // P1 has the lowest Y
public float Slope, Intercept; // set in constructor
public bool IsVertical;
public Line(Point p1, Point p2)
{
if (p1.Y > p2.Y) { P1 = p2; P2 = p1; } // p1 has lowest Y
else { P1 = p1; P2 = p2; }
IsVertical = (p1.X == p2.X);
if (!IsVertical) { Slope = (p2.Y - p1.Y) / (p2.X - p1.X); Intercept = p1.Y - Slope * p1.X; }
}
public void ExpandRanges(int[] minCol, int[] maxCol)
{
// start out at row, col where P1 is, which has lowest Y
int row = (int)(P1.Y / ROW_SIZE);
int col = (int)(P1.X / COL_SIZE);
int lastRow = (int)(P2.Y / ROW_SIZE);
int lastCol = (int)(P2.X / COL_SIZE);
// expand row to include P1
minCol[row] = Math.Min(col, minCol[row]); maxCol[row] = Math.Max(col, maxCol[row]);
// now we find where our line intercepts each horizontal line up to P2
float currY = P1.Y;
float currX = P1.X;
while (row < lastRow)
{
row = row + 1;
float rowY = row * ROW_SIZE;
float diffY = rowY - currY;
float diffX = IsVertical ? 0f : diffY / Slope;
currY = currY + diffY;
currX = currX + diffX;
col = (int)(currX / COL_SIZE);
// expand rows above and below dividing line to include point
minCol[row - 1] = Math.Min(col, minCol[row - 1]);
maxCol[row - 1] = Math.Max(col, maxCol[row - 1]);
minCol[row] = Math.Min(col, minCol[row]);
maxCol[row] = Math.Max(col, maxCol[row]);
}
// expand last row to include P2
minCol[lastRow] = Math.Min(lastCol, minCol[lastRow]);
maxCol[lastRow] = Math.Max(lastCol, maxCol[lastRow]);
}
public static void Test()
{
Point p1 = new Point(160, 250);
Point p2 = new Point(340, 250);
Point p3 = new Point(250, 40);
Line l1 = new Line(p1, p2);
Line l2 = new Line(p2, p3);
Line l3 = new Line(p3, p1);
Line[] lines = { l1, l2, l3 };
int rowCount = 4;
int[] minCol = new int[rowCount];
int[] maxCol = new int[rowCount];
for (int i = 0; i < rowCount; i++)
{
minCol[i] = int.MaxValue;
maxCol[i] = int.MinValue;
}
for (int i = 0; i < lines.Length; i++)
lines[i].ExpandRanges(minCol, maxCol);
for (int i = 0; i < rowCount; i++)
Console.WriteLine("Row {0}: {1} - {2}", i, minCol[i], maxCol[i]);
}
}
Produzione:
Row 0: 2 - 2
Row 1: 1 - 3
Row 2: 1 - 3
Row 3: 2147483647 - -2147483648
