Path: chuka.playstation.co.uk!news
From: Jim <jim@micronetics.com>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: 3D Sprite TMDs?
Date: Thu, 12 Feb 1998 09:54:48 +0000
Organization: PlayStation Net Yaroze (SCEE)
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References: <01bce267$32a34140$0300010a@mario>
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3d sprites rears its head again.. oh that old chestnut..

Has there been a solution to this problem yet?  I was up until the early hours
again this morning trying to
place a sprite in three dimensions.  I have something reasonable working, just
a couple of glitches here and there.  My major problem is I have a roving
camera style view and the sprite has trouble translating in relation to its
[camera] position.

Here's some pseudo code from what I can remember, am I doing anything unusual?

VECTOR v;    // coord system
VECTOR p;    // resulting location for sprite
MATRIX m;
long x,y;

v.vx = 0;  v.vy = 0;  v.vz = 0;
GsInitCoordinate2 ( WORLD, &local);        // init coord system
GsGetLS (&local, &m);                                // combine with
GsWSMATRIX for camera
ApplyMatrix (&m, &v, &p);                        // project coordinates

// perspective calcs and display here...

Now this code produces the expected result ( or at least I convinced myself
the result was expected).
But if I translate that point or coordinate system anywhere else, I get nada,
or something unexpected and a bit bizarre..

I've not shown the perspective calcs because they were a hack.
essentially.

x = -p.vx;
y = p.vz;        // not a typo with vz

But this does place the sprite where it should be..

Does ApplyMatrix add the translation terms as well?  I wrote my own version of
applymatrix to compare the
results and I got the same as ApplyMatrix only if I neglected to do the
translation.

I also get the same result if I replace the GsGetLs with
ApplyMatrix (&GsWSMATRIX, &v, &p);

I guess as an alternative to this I would have to try a bill boarding
approach, although not really ideal for the application I have in mind, and
quite possibly slower.

Can anyone please help me out, as I don't think I could handle many more
sleepless nights.


Many thanks
Regards

Jim

Mario Wynands wrote:

> I have noticed in the TMD descriptions that there is a sprite primitive
> available.  However, some brief experimentation has not resulted in a
> working sprite based TMD object, as my engine just dies (unsupported code
> error) when it tries to process a TMD with a single 'sprite' in it.
> RSDLink seems quite happy to make TMD objects with sprites in them though.
>
> Has anybody managed to get sprite based TMDs working?  Are they even
> supported by the Yaroze libs?
>
> Thanks in advance,
>
> Mario