RE: [Algorithms] Stopping shadow volumes from going through geometry

[Joris M. <jor...@pa...>]

this is what i mean, in "real-life" this is not possible. Usually the
static geom uses some prebaked form of shadowing (lightmap, vertex
darkening, whatever) and it will clash with the dynamic shadowcaster. We
only want the character to cast shadows on the vicinity using stencil
and leave the rest as-is. Ofcourse when your initials are JC and you are
making a game called D III things change a bit ;)
 
 
Joris

-----Original Message-----
From: gda...@li...
[mailto:gda...@li...] On Behalf Of John
Pollard
Sent: Friday, November 22, 2002 1:31 AM
To: gda...@li...
Subject: Re: [Algorithms] Stopping shadow volumes from going through
geometry


Hit reply too fast :-O
 
>>You don't even need to make the entire scene cast shadows
Actually, the character's shadow will still go through the wall.  But
you can simply make the wall cast shadows as well.  Since it's blocking
imcoming light, it works.  And no double darkening.
 

----- Original Message ----- 
From: John  <mailto:jo...@3d...> Pollard 
To: gda...@li... 
Sent: Thursday, November 21, 2002 6:23 PM
Subject: Re: [Algorithms] Stopping shadow volumes from going through
geometry

You won't get the double darkening if you do all your shadowvolumes at
once at the end, and do the fullscreen quad to darken, but it still
doesn't solve the problem completely, as the ledge will now go through
walls, and it's a never ending process, unless like you said, the whole
scene cast shadows.  But this method is such a pain, and you never
really fix all the problems.
 
Our shadowvolumes actually block imcoming light, so the problem goes
away (which is how most people are doing it these days I'm assuming).
The drawback, is you have to interleve your light rendering code between
the shadowvolume rendering.  The advantage, is all those problems go
away.  You don't even need to make the entire scene cast shadows.
Everything just works.
 

----- Original Message ----- 
From: Joris  <mailto:jor...@pa...> Mans 
To: gda...@li... 
Sent: Thursday, November 21, 2002 6:04 PM
Subject: RE: [Algorithms] Stopping shadow volumes from going through
geometry

this is the answer i see all the time when ppl ask this question (please
dont take this personally), but as we all know this doesnt solve it,
even with the ledge casting a shadow you will get "double shadowing"
under the ledge.
So if anyone has a way of solving this which does not require
stencil-shadowing the entire scene ;) please reply as i dont know it
either :|
 
 
Joris

-----Original Message-----
From: gda...@li...
[mailto:gda...@li...] On Behalf Of
Gilles Marion
Sent: Thursday, November 21, 2002 10:17 PM
To: gda...@li...
Subject: Re: [Algorithms] Stopping shadow volumes from going through
geometry


Hi,
 
I think the ledge should also cast its shadow onto the ground, no ?
If so, it doesn't matter if the shadow volume is extruded past the
ledge.
If fillrate is your bottleneck, think about clipping (cpu intensive), or
try setting the far side 
of the shadow volume nearer from the character.
If it's a sun-like light, radiosity of the environment should make look
that 
correct to your eyes.
 
Gilles.
 
----- Original Message ----- 

From: Fong,  <mailto:JF...@Bl...> Jay 
To: 'gda...@li...' 
Sent: Thursday, November 21, 2002 9:29 PM
Subject: [Algorithms] Stopping shadow volumes from going through
geometry


Hello,
 
I was wondering if there is some way to prevent shadows, generated by
the stencil shadow volume technique, from being extruded through other
objects in the scene?  e.g. a character standing on an overhanging ledge
above ground casts a shadow on the ledge but also onto the ground below
the ledge.
 
I thought about clipping the extruded shadow polys against the world
geometry but I'm hoping for a more elegant (i.e. simpler) solution since
our world geometry is quite dense.
 
Any solutions or links/pointers to papers related to this issue would be
much appreciated!
 
Thanks,
Jay