Path: chuka.playstation.co.uk!news From: "CRAIG GRAHAM" Newsgroups: scea.yaroze.programming.3d_graphics Subject: Re: Where to place my normals? Date: 12 Jan 1998 12:48:47 GMT Organization: Intelligent Research Ltd Lines: 24 Message-ID: <01bd1f59$7bf758c0$6c0b0a0a@newcastle.twowaytv.co.uk> References: <34B18E53.B74AAAC5@ix.netcom.com> <34B2A92B.446B@peace.co.nz> NNTP-Posting-Host: 194.131.235.3 X-Newsreader: Microsoft Internet News 4.70.1161 James Russell wrote in article <34B2A92B.446B@peace.co.nz>... [SNIP - Lot's of good stuff gone] > For instance, to speed up drawing times, the computer does not want > to draw polygons that are not visible. If you were drawing a single die > (a cube), then you only want to draw the faces facing you, since they > will cover the faces behind. Every face in the cube has a normal, and > the normals are defined in such a way that they point 'out', away from > the center of the cube. Then when you come to draw the scene, the > computer figures out which faces have normals pointing towards the > screen, and draws them, and ignores any polygons with normals facing > away from the screen. Interestingly, the Playstation doesn't actually use the Normal in the TMD primtive for this. I guess it's 'coz not all TMD primitives have a normal, and rather than special case, they just re-calculate for all primitives. The normal in the TMD is only used by the flat lighting / gourard shade functions. Craig.