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update point_in_prism #18

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update point_in_prism #18

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12 changes: 8 additions & 4 deletions utils/geom.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2149,10 +2149,14 @@ boolean intersect_line_with_segment(double px, double py, double dx, double dy,
double t = (M00*RHSy-M10*RHSx)/DetM;
if (s) *s = (M11*RHSx-M01*RHSy)/DetM;

if (t<0.0 || t>1.0) // intersection of lines does not lie between vertices
return 0;

return 1;
// the plumb line intersects the segment if 0<=t<=1, with t==0,1
// corresponding to the endpoints; for our purposes we count
// the intersection if the plumb line runs through the t==0 vertex, but
// NOT the t==1 vertex, to avoid double-counting for complete polygons.
#define DELTAT 1.0e-6
#define TMIN (0.0)
#define TMAX (1.0-DELTAT)
return ( ( t<TMIN || t>TMAX ) ? 0 : 1 );
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@stevengj stevengj Jul 11, 2018 •
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I usually prefer rounding to float for this kind of approximate comparison, i.e. wouldn't

return t < 0 || ((float)t) >= 1 ? 0 : 1;

work?

}

// like the previous routine, but only count intersections if s>=0
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