public void TryClipLiangBarsky_SegmentsOutsideCorners_Q1(
RectDecimal rect, SegmentDecimal seg1)
{
var actual = GridUtils.TryClipLiangBarsky(
rect,
seg1,
out var clippedSegment);
Assert.That(actual, Is.False);
}
public void TryClipLiangBarsky_CollinearSegmentsInsideCorrect_Q1(
RectDecimal rect, SegmentDecimal seg1, SegmentDecimal expected, decimal eps)
{
var actual = GridUtils.TryClipLiangBarsky(
rect,
seg1,
out var clippedSegment);
Assert.That(actual, Is.True);
Assert.That(clippedSegment.X1, Is.EqualTo(expected.X1).Within(eps));
Assert.That(clippedSegment.Y1, Is.EqualTo(expected.Y1).Within(eps));
Assert.That(clippedSegment.X2, Is.EqualTo(expected.X2).Within(eps));
Assert.That(clippedSegment.Y2, Is.EqualTo(expected.Y2).Within(eps));
}
public static bool TryClipLiangBarsky(RectDecimal rect, SegmentDecimal segment, out SegmentDecimal result)
{
result = new SegmentDecimal();
// defining variables
var p1 = -(segment.X2 - segment.X1);
var p2 = -p1;
var p3 = -(segment.Y2 - segment.Y1);
var p4 = -p3;
var q1 = segment.X1 - rect.X;
var q2 = rect.XMax - segment.X1;
var q3 = segment.Y1 - rect.Y;
var q4 = rect.YMax - segment.Y1;
var posArr = new decimal[5];
var negArr = new decimal[5];
var posInd = 1;
var negInd = 1;
posArr[0] = 1;
negArr[0] = 0;
if ((p1 == 0 && q1 < 0) || (p2 == 0 && q2 < 0) || (p3 == 0 && q3 < 0) || (p4 == 0 && q4 < 0))
{
// Line is parallel to clipping window!
return(false);
}
if (p1 != 0)
{
var r1 = q1 / p1;
var r2 = q2 / p2;
if (p1 < 0)
{
negArr[negInd++] = r1; // for negative p1, add it to negative array
posArr[posInd++] = r2; // and add p2 to positive array
}
else
{
negArr[negInd++] = r2;
posArr[posInd++] = r1;
}
}
if (p3 != 0)
{
var r3 = q3 / p3;
var r4 = q4 / p4;
if (p3 < 0)
{
negArr[negInd++] = r3;
posArr[posInd++] = r4;
}
else
{
negArr[negInd++] = r4;
posArr[posInd++] = r3;
}
}
var rn1 = MaxI(negArr, negInd);
var rn2 = MinI(posArr, posInd);
if (rn1 > rn2)
{
// reject
// Line is outside the clipping window!
return(false);
}
var xn1 = segment.X1 + p2 * rn1;
var yn1 = segment.Y1 + p4 * rn1;
var xn2 = segment.X1 + p2 * rn2;
var yn2 = segment.Y1 + p4 * rn2;
result = new SegmentDecimal(
new Vector2Decimal(xn1, yn1),
new Vector2Decimal(xn2, yn2)
);
return(true);
}
