[Radiance-general] Re: Major Axis definition

[Greg Ward]

Hi Marcus,

The "major axis" is the dominant component in the surface normal vector 
(the axis with the largest absolute value).  Since barycentric 
coordinates are defined in two dimensions, I throw away the major axis 
direction as it is the one most perpendicular to the plane of the 
triangle, and I just use the other two.  This is no less accurate than 
doing a fancy projection and a whole lot cheaper.

The functions defined in tmesh.h and tmesh.c in src/common/ should help 
you out.

-Greg

> From: "Marcus Jacobs" <marcdevon at hotmail.com>
> Date: March 2, 2004 11:31:17 AM PST
>
> Dear Group
>
> I am looking into using tmesh.cal in order to map patterns onto 
> polygons with a Radiance converter that I have written. In tmesh.cal, 
> it defines the first argument as :
>
> A1 = Major axis (0==X, 1==Y, 2==Z)
>
>
> I have no clue to exactly what this is. Could anyone *coughGreg* 
> provide an explaination of this.
>
>
> Thanks
>
>
> Marcus