Path: chuka.playstation.co.uk!news From: Christoph Luerig Newsgroups: scee.yaroze.programming.3d_graphics Subject: Re: Vectors and Matrices Mini Tutorial Date: Fri, 10 Jul 1998 14:12:06 +0200 Organization: PlayStation Net Yaroze (SCEE) Lines: 97 Message-ID: <35A60516.ED4487A1@immd9.informatik.uni-erlangen.de> References: <35A25BBF.F272A126@scee.sony.co.uk> <35A5DCF1.10D9E988@immd9.informatik.uni-erlangen.de> <35A5E3E1.488F60AF@scee.sony.co.uk> NNTP-Posting-Host: faui90.informatik.uni-erlangen.de Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------------36F68AF69C34F51635DEF31B" X-Mailer: Mozilla 4.04C-SGI [en] (X11; I; IRIX 6.3 IP32) --------------36F68AF69C34F51635DEF31B Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit James Russell wrote: > > > U = W * (W.vz^-1 * [ H 0 0 0 ] ) > [ 0 H 0 0 ] > [ 0 0 H 0 ] > [ 0 0 0 W.vz ] > > W.vz^-1 = 1/W.vz Oups, that looks funny, besides the z-component of W appearing in the matrix, I would suspect something like (H+W.vz) as the last entry if you want to insert values of W into this matrix at all. I would have suspected something with the structure: [H 0 * 0] [0 H * 0] [0 0 * 1] [0 0 * H] As Ynew=(H*Yold)/(H+Zold); The * sysmbols depend on what you actually do with the z-values. What brings me up to the next question: Up to now I assumed (but I did not find it anywhere explicitely), that the z-values used for the ordering tables are the ones used after the application of the LS matrix but before the application of the perspective projection, is that correct (it would be relevant for stability aspects)? Christoph --------------36F68AF69C34F51635DEF31B Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit James Russell wrote:
 

U = W * (W.vz^-1  * [  H    0    0     0   ] )
                    [  0    H    0     0   ]
                    [  0    0    H     0   ]
                    [  0    0    0    W.vz ]

W.vz^-1 = 1/W.vz

Oups, that looks funny, besides the z-component of W appearing in the matrix, I would suspect something like (H+W.vz)
as the last entry if you want to insert values of W into this matrix at all. I would have suspected something with
the structure:
[H 0 * 0]
[0 H * 0]
[0 0 * 1]
[0 0 * H]



As Ynew=(H*Yold)/(H+Zold); The * sysmbols depend on what you actually do with the z-values. What brings me up to



the next question: Up to now I assumed (but I did not find it anywhere explicitely), that the z-values used for



the ordering tables are the ones used after the application of the LS matrix but before the application of the



perspective projection, is that correct (it would be relevant for stability aspects)?






Christoph




 

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