CGAL users discussion list

[gupta61 <>]

Hi,

We just encountered another bug in CGAL in segment triangle intersection. I
am trying to find out intersection between the segment and a triangle. 

The segment is defined by 

CGALSegment3 segment_query( CGALPoint3(2.1, 2, 0.5), 
                              CGALPoint3(3.23135, 2, 0.5) );

and the triangle by

CGALTriangle3 triangle( CGALPoint3(2.18182, 1.81818, 0.666667) /* vertex
0*/,
                          CGALPoint3(2.18182, 2, 0.5) /* vertex 2*/,
                          CGALPoint3(2.09091, 1.90909, 0.5833335) /* vertex 
3*/

We are using exact predicates and inexact constructions. 

The output we are getting is as follows:

Segment query: 2.1 2 0.5 3.23135 2 0.5
 
Triangle: 2.18182 1.81818 0.666667 2.18182 2 0.5 2.09091 1.90909 0.5833335

CGAL::do_intersect (0/1) = 1

Encountered intersection object is a point (for the segment)
         2.1 2 0.5

Encountered intersection object_oppos is a point (for segment.opposite())
1.89801666666667 2 0.5



If we use exact constructions we get the right result. Let me know if I am
missing anything here.

BTW, the correct result is 

Segment query: 2.1 2 0.5 3.23135 2 0.5
 
Triangle: 2.18182 1.81818 0.666667 2.18182 2 0.5 2.09091 1.90909 0.5833335

CGAL::do_intersect (0/1) = 1

Encountered intersection object is a point
     2.18182 2 0.5

Encountered intersection object_oppos is a point
     2.18182 2 0.5


-----
Piyush Gupta
UIUC
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