Path: chuka.playstation.co.uk!chuka.playstation.co.uk!news
From: Jim <jim@micronetics.com>
Newsgroups: scee.yaroze.beginners
Subject: Re: Beginners 3D Questions
Date: Mon, 22 Sep 1997 14:26:44 +0100
Organization: PlayStation Net Yaroze (SCEE)
Lines: 112
Message-ID: <34267214.541C94E8@micronetics.com>
References: <01bcc069$85cdfe20$c793989e@fourny.demon.co.uk> <341D0A2C.801EF566@micronetics.com> <01bcc1c3$c7f77c80$c793989e@fourny.demon.co.uk>
NNTP-Posting-Host: jim.micronetics.com
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Mailer: Mozilla 4.01 [en] (Win95; I)
X-Priority: 3 (Normal)

Graeme Evans wrote:
> 
> Jim. Your demo is one of my favourites (can't wait for the Make-a-chip
> bit).

Thanks, that means a lot to me.  At least it looks like I'm heading down
the right path.  Currently I've not done much on it as I'm currently
working on realtime compression stuff.  Expect something real soon now.

> Can I rather cheekily ask you some questions about it & steal all
> your ideas?

Sure, fire away.

> 
> > >
> > > (a)     Lit gourard quads and triangles dont work, or rather the lighting
> > > doesnt work
> >
> 
> What did
> you do to get them working? Anything special?

I created the objects in 3ds, (now I use lightwave) exported them as dxf
and did dxf2rsd with the gouraud option on.  Now I used the lightwave
plug in and export directly it rsd.  I don't think I hit any noticeable
problems with this and it was about 2 months ago, so I could have
selectively forgotten it all.

> 

> >
> > I played with this in theory but thought that it would be far too much
> > work to run though a tmd and tweak the normals each frame just for the
> > lighting.  If you look at my robot demo (playstation.co.uk/~Sig1LL) I
> > don't use any of GsLibs lighting or fogging effects.
> 
> No fogging? How did you get the maze to appear out of darkness? 

I wrote the fogging myself.  I just find the distance from the viewer to
each tile and alter the light intensity based on the distance.

>Did you
> alter the RGB values of the floor polys and robots as they get further
> away? 

Yep for each vertices of the polygon, I just scale it on the distance.


>What about that cool green glow? It looks too circular to be done the
> same way. 

Its done it exactly the same way.  I just calculate the distance from
the emitter to each tile vertices and calculate an intensity on that.

>Is it a separate set of green polys with transparency set you
> draw over the floor?

Nope.  I just tweak each RGB triple for each poly vert. 

> 
> Do you get a better resolution with libgs fogging, for example does it
> gradate a fog effect over a single poly so the back of it is more faded
> than the front? 

The major bonus is that my fogging is actually spherical.  I don't pay
attention to the polygon normals so  back facing polys would be lit
exactly the same as forward.  It would be quite trivial to fix, but I
don't estimate it to be a major glitch.  So it  would probably never be
fixed.

>When you say it only works with black and white does that
> mean it can only fade to black 
> or that all your polys have to be greyscale?

Ah no.  gslib will only depth cue polys to black (I think).  So a faded
out poly would look really strange against a red background.  (if you
see what I mean)

> 
> > > I guess subdivision is to do with how you draw polys when half of them
> > > sticks off the screen (like the floor in dungeon);
> 
> I'm being a bit lazy here and I suppose I should really write some code and
> try it, but if say you have one of your nice textured floor quads and maybe
> 10% of it (say the bottom left corner) is off the bottom of the screen,
> does that mean it doesnt get drawn unless you subdivide or do I have
> totally the wrong idea here?

All changed now. :-)  I don't do any of my own subdivision now.  I
managed to totally eradicate it.  (probably a good thing too.)  I've
tweaked the view distance so not may disappear and GsDIV1 (I think)
seems to suffice for ones that will split.
> 

> 
> Do you have this split TMD arrangement for your floor, where your near
> objects are in one tmd (with subdivision turned on) and the far ones in
> another? And each time you subdivide by two, do the polys divide exactly in
> the middle?

Each tile in the world is just one tmd.  Which is why the the rgb
tweaking to so trivial.

> 
> Oh so many questions.

Fire away.  All too happy to help.  I'll be releasing the source once it
is readable.

> 
> Graeme