ACIS - parameters on a spherical surface

[Ang Pin Yang]

Hello all, I am having a problem in using ACIS geometric modelling package. 
Hope you all can enlighten me.

>From what I know, when a CAD spherical surface is exported to ACIS format 
(*.sat), ACIS will use the surface's orthogonal circumcircles (both with the 
sphere center as its center) as the u and v axis (u,v serve as the parameters).

My problem is, if I got a {u,v} coordinate, and I want to find the 
corresponding 3D position on this spherical surface. The ACIS interface will, 
occasional, return a point which is not at the expected location, because there 
are two points on this surface have the same {u,v} value. 

Can anyone please tell me how to handle this problem? 

Thanks a lot.

Regards,
Pin Yang

---------------------------------------------------------------------------
Ang Pin Yang
Finite Element Modeling Group
School of Mechanical & Manufacturing Engineering
The Queen's University of Belfast
Ashby Building
Stranmillis Road
Belfast BT9 5AH
Northern Ireland
United Kingdom
Tel: +44 02890 274277
   
http://sog1.me.qub.ac.uk/members/pin_yang/pin.html


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