Path: chuka.playstation.co.uk!scea!greg_labrec@interactive.sony.com
From: mperdue@l4software.com (Mario Perdue)
Newsgroups: scea.yaroze.programming.3d_graphics
Subject: Re: Where to place my normals?
Date: Tue, 06 Jan 1998 04:12:35 GMT
Organization: L4 Software
Lines: 35
Message-ID: <34b1ab34.14169234@205.149.189.29>
References: <34B18E53.B74AAAC5@ix.netcom.com>
NNTP-Posting-Host: firewall.hrtc.net
X-Newsreader: Forte Free Agent 1.11/32.235

Manny,

You really havn't given enough information to answer your question. 

The normal will depend on the plane that the polygon lies in. The
normal vector is basicly the end point of a unit length vector that
defines the Z direction of the plane. So, if you have a polygon that
goes through these endpoints:

    0,    0,    0
 4096,    0,    0
 4096, 4096,    0
    0, 4096,    0

your normal vector could be:

    0,    0, 4096   OR   0,    0,-4096

This vector is obtained by doing a cross product of the vectors that
define the X and Y axis and then scaling the vector to unit length.

Mario

On Mon, 05 Jan 1998 19:52:20 -0600, Manny Najera
<mannyn@ix.netcom.com> wrote:

>I haven't seen much information posted about how to use normals in a
>polygon.  The only coordinates I've seen given to a normal were just
>variations of the same three numbers: (0, 4096, 0).  For a regular
>square polygon, where the center is at (0, 0, 0), and the sides are ten
>units long, what would be the coordinates of the normal?
>
>Manny Najera
>