In article <3f09a148$1@news.povray.org>,
 "Greg M. Johnson" <gregj:-)565### [at] aolcom> wrote:

> With the trace function, it will return an <a,b,c>.  What meaning does
> <a,b,c> have way out on surface point <d,e,f>, unless it means parallel to a
> vector {<0,0,0>, <a,b,c>}?,   or  the vector {<d,e,f>,<d+a, e+b, f+c> }?

It means the interesection is at the point represented by the vector < 
a, b, c>. "{<0,0,0>, <a,b,c>}" is not a vector, it is two vectors, 
representing either a line segment or a ray (I'm not sure which you are 
thinking of). A vector is a mathematical construct with direction and 
magnitude, nothing more. POV represents a vector as 3 floating point 
values for x, y, and z coordinates.

Or if you were talking about the normal value returned through the 
parameter, that is a direction vector. The normal points in the 
direction given by < a, b, c>. The intersection point is irrelevant.

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

Post a reply to this message