/// <summary> /// Distance to a point. /// </summary> /// <param name="ptTest">The test point.</param> /// <param name="ptOnThis">Output. The closest point on the triangle.</param> public double Distance(C2DPoint ptTest, C2DPoint ptOnThis) { double dArea = GetAreaSigned(); bool BTemp = true; // Construct the lines. C2DLine Line12 = new C2DLine(P1, P2); C2DLine Line23 = new C2DLine(P2, P3); C2DLine Line31 = new C2DLine(P3, P1); if (dArea == 0) { // Colinear so find the biggest line and return the distance from that double d1 = Line12.GetLength(); double d2 = Line23.GetLength(); double d3 = Line31.GetLength(); if (d1 > d2 && d1 > d3) return Line12.Distance(ptTest, ptOnThis); else if (d2 > d3) return Line23.Distance(ptTest, ptOnThis); else return Line31.Distance(ptTest, ptOnThis); } // Find out it the triangle is clockwise or not. bool bClockwise = dArea < 0; // Set up some pointers to record the lines that the point is "above", "above" meaning that the // point is on the opposite side of the line to the rest of the triangle C2DLine LineAbove1 = null; C2DLine LineAbove2 = null; // Find out which Lines have the point above. if ( Line12.IsOnRight( ptTest ) ^ bClockwise ) // if the pt is on the opposite side to the triangle LineAbove1 = Line12; if ( Line23.IsOnRight( ptTest ) ^ bClockwise) { if (LineAbove1 != null) LineAbove2 = Line23; else LineAbove1 = Line23; } if ( Line31.IsOnRight( ptTest ) ^ bClockwise) { if (LineAbove1 != null) { // We can't have all the lines with the point above. Debug.Assert(LineAbove2 != null); LineAbove2 = Line31; } else LineAbove1 = Line31; } // Check for containment (if there isn't a single line that its above then it must be inside) if (LineAbove1 == null) { // Pt inside so project onto all the lines and find the closest projection (there must be one). // Set up a record of the point projection on the lines. C2DPoint ptOnLine = new C2DPoint(); bool bSet = false; double dMinDist = 0; if (ptTest.ProjectsOnLine(Line12, ptOnLine, ref BTemp)) { dMinDist = ptTest.Distance(ptOnLine); ptOnThis.Set(ptOnLine); bSet = true; } if (ptTest.ProjectsOnLine(Line23, ptOnLine, ref BTemp)) { double dDist = ptTest.Distance(ptOnLine); if (!bSet || dDist < dMinDist) { dMinDist = dDist; ptOnThis.Set(ptOnLine); bSet = true; } } if (ptTest.ProjectsOnLine(Line31, ptOnLine, ref BTemp)) { double dDist = ptTest.Distance(ptOnLine); if (!bSet || dDist < dMinDist) { dMinDist = dDist; ptOnThis.Set(ptOnLine); bSet = true; } } Debug.Assert(bSet); return -dMinDist; //-ve if inside } else if (LineAbove2 == null) { // it is only above 1 of the lines so simply return the distance to that line return LineAbove1.Distance(ptTest, ptOnThis); } else { // It's above 2 lines so first check them both for projection. Can only be projected on 1. // If the point can be projected onto the line then that's the closest point. C2DPoint ptOnLine = new C2DPoint(); if (ptTest.ProjectsOnLine(LineAbove1, ptOnLine, ref BTemp)) { ptOnThis = ptOnLine; return ptOnLine.Distance(ptTest); } else if (ptTest.ProjectsOnLine(LineAbove2, ptOnLine, ref BTemp)) { ptOnThis = ptOnLine; return ptOnLine.Distance(ptTest); } else { // The point doesn't project onto either line so find the closest point if (LineAbove1 == Line12) { if (LineAbove2 == Line23) { ptOnThis = P2; return ptTest.Distance(P2); } else { ptOnThis = P1; return ptTest.Distance(P1); } } else { ptOnThis = P3; return ptTest.Distance(P3); } } } }
/// <summary> /// Distance to a point. /// </summary> /// <param name="ptTest">The test point.</param> /// <param name="ptOnThis">Output. The closest point on the triangle.</param> public double Distance(C2DPoint ptTest, C2DPoint ptOnThis) { var dArea = GetAreaSigned(); var BTemp = true; // Construct the lines. var Line12 = new C2DLine(P1, P2); var Line23 = new C2DLine(P2, P3); var Line31 = new C2DLine(P3, P1); if (dArea == 0) { // Colinear so find the biggest line and return the distance from that var d1 = Line12.GetLength(); var d2 = Line23.GetLength(); var d3 = Line31.GetLength(); if (d1 > d2 && d1 > d3) { return(Line12.Distance(ptTest, ptOnThis)); } else if (d2 > d3) { return(Line23.Distance(ptTest, ptOnThis)); } else { return(Line31.Distance(ptTest, ptOnThis)); } } // Find out it the triangle is clockwise or not. var bClockwise = dArea < 0; // Set up some pointers to record the lines that the point is "above", "above" meaning that the // point is on the opposite side of the line to the rest of the triangle C2DLine LineAbove1 = null; C2DLine LineAbove2 = null; // Find out which Lines have the point above. if (Line12.IsOnRight(ptTest) ^ bClockwise) // if the pt is on the opposite side to the triangle { LineAbove1 = Line12; } if (Line23.IsOnRight(ptTest) ^ bClockwise) { if (LineAbove1 != null) { LineAbove2 = Line23; } else { LineAbove1 = Line23; } } if (Line31.IsOnRight(ptTest) ^ bClockwise) { if (LineAbove1 != null) { // We can't have all the lines with the point above. Debug.Assert(LineAbove2 != null); LineAbove2 = Line31; } else { LineAbove1 = Line31; } } // Check for containment (if there isn't a single line that its above then it must be inside) if (LineAbove1 == null) { // Pt inside so project onto all the lines and find the closest projection (there must be one). // Set up a record of the point projection on the lines. var ptOnLine = new C2DPoint(); var bSet = false; double dMinDist = 0; if (ptTest.ProjectsOnLine(Line12, ptOnLine, ref BTemp)) { dMinDist = ptTest.Distance(ptOnLine); ptOnThis.Set(ptOnLine); bSet = true; } if (ptTest.ProjectsOnLine(Line23, ptOnLine, ref BTemp)) { var dDist = ptTest.Distance(ptOnLine); if (!bSet || dDist < dMinDist) { dMinDist = dDist; ptOnThis.Set(ptOnLine); bSet = true; } } if (ptTest.ProjectsOnLine(Line31, ptOnLine, ref BTemp)) { var dDist = ptTest.Distance(ptOnLine); if (!bSet || dDist < dMinDist) { dMinDist = dDist; ptOnThis.Set(ptOnLine); bSet = true; } } Debug.Assert(bSet); return(-dMinDist); //-ve if inside } else if (LineAbove2 == null) { // it is only above 1 of the lines so simply return the distance to that line return(LineAbove1.Distance(ptTest, ptOnThis)); } else { // It's above 2 lines so first check them both for projection. Can only be projected on 1. // If the point can be projected onto the line then that's the closest point. var ptOnLine = new C2DPoint(); if (ptTest.ProjectsOnLine(LineAbove1, ptOnLine, ref BTemp)) { ptOnThis = ptOnLine; return(ptOnLine.Distance(ptTest)); } else if (ptTest.ProjectsOnLine(LineAbove2, ptOnLine, ref BTemp)) { ptOnThis = ptOnLine; return(ptOnLine.Distance(ptTest)); } else { // The point doesn't project onto either line so find the closest point if (LineAbove1 == Line12) { if (LineAbove2 == Line23) { ptOnThis = P2; return(ptTest.Distance(P2)); } else { ptOnThis = P1; return(ptTest.Distance(P1)); } } else { ptOnThis = P3; return(ptTest.Distance(P3)); } } } }