BUG in AcGeLineSeg3d::intersectWith

Hi,

I have been using Autocad for a few days, but I have just discovered a bug into.

It is about the function intersectWith.

If I get 2 segments, which have a point in common, this function returns sometimes true, sometimes false.

Here is an example. I get the first segment to be [ 300.0 0.0 0.0] [100.0 0.0 0.0], and the other segment to be [0.0 gap 0.0 ] [100.0 0.0 0.0]. When I make a while with the gap varying in the interval [0 1], with the ratio 1/10^10, res is sometimes true (intersection), sometimes false (not intersected).

AcGePoint3d pt1Adl(0.00000000 ,0.00000000+gap,0.00000000);

AcGePoint3d pt1Bdl(100.0000000 ,0.00000000,0.00000000);

AcGePoint3d pt2Adl(300.00000000 ,0.00000000 ,0.00000000);

AcGePoint3d pt2Bdl(100.00000000 ,0.00000000 ,0.00000000);

AcGeLineSeg3d lSeg1dl(pt1Adl,pt1Bdl);

AcGeLineSeg3d lSeg2dl(pt2Adl,pt2Bdl);

res = lSeg1dl.intersectWith(lSeg2dl,ptInsd1,tol);

This is strange. I used a tolerance of tol=0.1, sometimes .01.

Can somebody (a mathematician) help me understand what it is happenning ?

Thanks in advance for any help

I was tempted to say this was a binary to decimal precision problem, but your tolerance setting should have accounted for that. Still, working that close to the margin

with the ratio 1/10^10

 

on double precision floating point operations will be risky.

There aren’t that many ARX programmers on this forum. You may be able to get more responses at http://www.theswamp.org/

I see. thanks.