In article <3d9b7fe7@news.povray.org>,
 "Corey Woodworth" <cdw### [at] mpinetnet> wrote:

> I've seen lots of cool stuff done with trace but I've never dabbled with it
> myself. I read the docs on it and I'm a bit confused. I have a heightfield
> named canyon, and this is a nested loop to test for an intersection. It
> should always intersect so it should always generate a sphere (I havn't the
> slightest how to test for the slope yet), but it loops infinetly and I dunno
> why. I'm not too good at Macros yet. =)
> Here is my code, can someone point me in the right direction?

Well, your first problem is that you are testing for equality in your 
loop conditions...almost always a Bad Thing. Scalar variables in POV-Ray 
are double-precision floating point numbers, and numeric errors could 
cause them to go right past 0 without ever being exactly equal to it. 
Normally, you loop while the counter variable is higher or lower to a 
value instead of while it is not equal to a certain value.

You are also looping down, this is just odd, since usually people loop 
up unless they have a good reason, but it works, there isn't any reason 
not to.

Finally, and probably the real reason you have a problem, the trace() 
function takes a ray direction, not an end point. All your trace() calls 
are going off in a plane perpendicular to the y axis and passing through 
< 0, 2, 0>. Use "trace(Canyon, Start, -y, Norm)" instead.

Oh, and you are missing an #end...I assume this just got lost in editing 
for the post, because the code doesn't do anything without it.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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