Path: chuka.playstation.co.uk!news
From: "Christoph Lürig" <CLuerig@aol.com>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: GsGetLw - Anyone?
Date: Wed, 15 Jul 1998 23:32:47 +0200
Organization: PlayStation Net Yaroze (SCEE)
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Hi Alex!

The Lw Matrix dexribes the transformation of the local coordinate system to
the world coordinate system. The lihting subsystem
of the PSX needs this matrix to perform the calculations (probably for the
transformation of the normal vectors of surface elements). The Ls Matrix
transforms the local coordinates into viewing coordinates, where the origin
is positioned at the Viewing Reference Point and the Z-Axis is pointing into
viewing direction and the -Y-Axis is poiting into the viewing up vector
direction. The Application of the Ls Matrix is perfomed juts before the
perspective transformation is done. As you ussually perform lighting and
drawing of an object, you have this GsGetLws method that returns both
matrices.

Alex Herbert wrote:

> Hi all.
>
> Right, I've sussed all the 2D stuff, and now I'm starting on 3D.  I've
> written a simple program which throws a few flat shaded dodecahedrons
> about the screen.  Everything fine so far, but, I don't understand how
> or why I should use the GsGetLw/GsGetLws functions.  Obviously I'm using
> GsGetLs successfully and all seems fine.  The manuals confuse me on
> this.  They seem to suggest it has something to do with lighting but I'm
> not sure.  The Library Reference gives exactly the same explanation for
> both GsGetLs and GsGetLw.
>
> Can anyone tell me in simple terms what GsGetLw is for, or maybe
> describe a situation where it would be used.
>
> Thanks,
>
> Herbs