Re: [Plib-users] Problems using sgIsectPlanePlane(), point is always at 0, 0, 0

[Satz K. <sat...@go...>]

Thanks, I got it working :-)


On 9/20/11, Fay, John F Dr CTR USAF AFMC AAC/XRS
<joh...@eg...> wrote:
> Elmi,
>
> 	Hello and welcome to the PLIB community.
>
> 	I think the problem is that you are using relative vectors when
> making your planes.  If you say "sgMakePlane ( plane1, a1, b1, c1 )" and
> "sgMakePlane ( plane2, a2, b2, c2 )" you will get nonzero values for
> your "point".  The three vectors in "sgMakePlane" are the vectors from
> the origin to the three points that define the plane.
>
> John F. Fay
> Technical Fellow, Modeling and Simulation
> Jacobs Technology / TEAS Group
> P.O. Box 1935, Eglin AFB, FL  32542-5000
> 850-883-3496
>
>
> -----Original Message-----
> From: Satz Klauer [mailto:sat...@go...]
> Sent: Tuesday, September 20, 2011 2:16 AM
> To: pli...@li...
> Subject: [Plib-users] Problems using sgIsectPlanePlane(),point is always
> at 0, 0, 0
>
> Hi,
>
>  I want to find the intersection line out of two planes but fail
>  miserably. That's what I'm doing:
>
>  - I start with two triangles a1,b1,c1 and a2,b2,c2 that describe my
>  planes and consist of three coordinates x,y and z for every corner of
>  it
>  - out of their corner coordinates x,y and z I calculate 3D vectors
>  sgVec3 va1,vb1,vc1 by substracting the coordinate values b1-a1, c1-b1,
>  a1-c1 and normalizing the result; the same is done for the second
>  triangle's coordinates
>  - then I call
>
>  sgMakePlane (plane1,va1,vb1,vc1);
>  sgMakePlane (plane2,va2,vb2,vc2);
>  ret=sgIsectPlanePlane (point,dir,plane1,plane2 );
>
>  But here the result is unusable and nearly every time the same.
>  "point" always contains _very_ small values so that after rounding to
>  6 decimal places the coordinates of it are 0,0,0.
>
>  What am I doing wrong here?
>
>  Elmi
>
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