RE: [Algorithms] Doom lightmaps

[Akbar A. <sye...@ea...>]

>* They only really work for dynamic lights and typically you can only
>have a few on screen before your frame rate suffers very badly.

yeah, this does suck. just one of the trade offs we have to take.
but these techniques are pretty suited for dark/scary games IMHO "right
now"..,
primarily due to the fact that the cpu/gpu's aren't ready to say, "light up
a scene like q3dm12
without the frame rate dying."


>We don't use shadow maps (== nasty horrible artifacts).
well there not really _that_ "nasty", esp after you take a look
at that terminal reality engine movie demo thingy..
in fact it' looked pretty cool..


>start with a GeForce 3 and burn fill-rate to implement a stencil
>buffer shadowing algorithm.
it can be a geforce 1/2 as well...

personally i don't plan on using _any_ of the geforce3's features that
aren't in hardware on the geforce 1X series.
and iirc, nv_vertex_program is implemented in hardware in release 10 drivers
and beyond.?

Personally,  550 US $ for a graphics chip is a quite a bit for an average
consumer, and i think the "buying computer frenzy" is pretty much over.
i think people are happy with there 'new' computers and video cards
(geforce2's and 1's) that came on there machines, and there satisfied with
the performance there getting on there apps (AIM, ICQ, word, ie, media
player )  ....

>he smooth shadows look like projected textures and you could easily do an
effect like a rotating
>fan using an animated projective texture or even better using the texture
remember, pretty much everything is 'uniformed'..
calculating silhouettes could possibly be where a perf hit is at?
i haven't done this on any thing high mesh related data sets where i'd see a
hit...

jason zisk wrote:
>move or is extremely small(soda cans, etc) I use a stencil shadow and for
>everything else I use pre-computed lightmaps.
neat, from the pictures i saw this looks like it 'suits your game' pretty
well ;)
a lot of people do want totally dynamic worlds.

like maybe running with a shadow so your always dark,
sounds like a cool idea to me. "Sounds like a mission for James Bond", well
maybe not.
Bond would come in with all sorts glory/lights/girls/action/guns and fancy
electronic gadgets,
no need for him to be sneaking around :-)

you can't use a lightmap used for global illumination to do this kinda of
thing..

and shadow maps really do need a lot of extra work for say a point light.


i think for level and game designers, it will take some adjusting till they
get in the mind
set that each light (visible to viewer) has a cost factor attached to it ..


very bored, starving and tired of seeing *"George Geczy" #!!@#%@%
-akbar A.

*has to do with the dx mailing list getting spammed horribly. can't
unsubsribe either :(
KILL the list @#%@%

;vertexabuse.cjb.net
or
;www.vertexabuse.com
cjb goes down once in a while


"plastic or metallic.
please pick your version of lighting ;) "
.me

-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of Alex
Clarke
Sent: Monday, February 26, 2001 3:32 AM
To: 'gda...@li...'
Subject: RE: [Algorithms] Doom lightmaps


We don't use shadow maps (== nasty horrible artefacts).
Adding full on volumetric shadows to an engine is not a
light weight thing to do.

Depending on the method used, they tend to:

* Burn fill rate
* Stencil methods in particular have very variable fill rate cost
* Require skinning to be done CPU side (so you can calculate the silhouette)
* Require fancy silhouette extraction algorithms (brute force extraction =
expensive)
* Require extremely accurate raycasts (to determine if the camera is shadow)
* Require a very near clipping plane (so you _have_ to use a z-buffer)
* Mess up loads of lighting optimisations (coalescing multiple lights into
an average light doesn't work well due to the shadows affecting the
blending)
* They only really work for dynamic lights and typically you can only
have a few on screen before your frame rate suffers very badly.
* Force the artists to cap objects
* Make it essential for all meshes to be manifold
* May make lit semi-transparent materials a total nightmare
* Require the artists to be very careful when modelling to avoid
unfortunate self shadowing.
* Require that the artists and designers don't try to use too many
polys. You can forget about having 100k triangle / frame scenes with
full on volumetric shadows

However,

They are quite pretty.

Alex Clarke, Programmer
Argonaut Games PLC

> > It is funny you mention the stencil+shadow map method
> because that is
> > exactly how I do dynamic shadows in my engine.  For any
> object that might
>
> I think that's also what they do in Malice (just my guesses
> of course).
>
>
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> GDA...@li...
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