Re: Isect

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Angus Dorbie (dorbie++at++sgi.com)
Tue, 21 Apr 1998 07:47:03 -0700

> Bemis, Suzie CEI-TACCSF wrote:
>
> Hi All,
>
> We're running a Line-of-Sight program which uses performer libraries
> and isect to calculate the height of terrain given a certain lat/lon
> that has been converted to x,y positions. There are some points on
> the database which are not returning valid isect hits. I've run some
> tests and have determined that there are some points within a certain
> polygon which return a valid isect and within the same polygon there
> are other points which don't have valid isect returns.
>
> I don't know what else to try to figure this one out. I didn't write
> the code. Of course the person who did has since left.
>

This came up recently,

Have you computed the geometry bound box correctly?

Have you changed the geometry, some data is cached by the isector
traversal so you need to avoid cacheing of this data where you are
changing the geometry.

Cheers,Angus.

-- 
"Only the mediocre are always at their best." -- Jean Giraudoux 


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