Path: chuka.playstation.co.uk!news From: Alex Herbert Newsgroups: scee.yaroze.programming.3d_graphics Subject: Re: What is a normal? Date: Fri, 14 Aug 1998 13:26:28 +0000 Organization: PlayStation Net Yaroze (SCEE) Lines: 23 Message-ID: <35D42CF4.A08257E5@ndirect.co.uk> References: <35D3F965.D5D79825@nospam.easynet.co.uk> <35D402A6.8830674@parny.force9.co.uk> <01bdc76a$e03e9320$230b0a0a@Angela1.intelligent-group.com> Reply-To: aherbert@ndirect.co.uk NNTP-Posting-Host: dialin2-22.ndirect.co.uk Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.04 [en] (Win95; I) Craig Graham wrote: > Get a sheet of A4 paper. Poke a pencil though it.Look at it side on. > There's a normal vector. > It points in the direction a polygon is facing. That's all. > > These are precalculated in PSX models ('coz it's quicker to rotate a vector > than to calculate > the vector from scratch). > Just to add my bit... A normal basically describes which way a polygon is facing. The Gs libs use normals to calculate lighting. The very good example that Graig gives would be appropriate for flat shaded polygons. With Gouraud (smooth) shading, vertex normals are used. In this case there is 1 normal per vertex rather than 1 normal per poly. The clever thing about normals is that they can be rotated in exactly the same way as vertices. Herbs