RE: [Algorithms] Portal VS BSP

[Greg S. [work] <gr...@st...>]

For what it's worth, Call of Duty doesn't allow doors or windows to be
opened/closed.  I'm not sure if this was a design decision or something =
that
made it easier for them to not have to deal with dynamic visibility.  =
Make
of that what you will =3D)

> -----Original Message-----
> From: gda...@li... =
[mailto:gdalgorithms-
> lis...@li...] On Behalf Of De Boer
> Sent: Saturday, December 13, 2003 12:59 PM
> To: gda...@li...
> Subject: [algorithmslist] [Algorithms] Portal VS BSP
>=20
> I read that call of duty uses a portal rendering algorithm rather than
> BSP.
> They state that "to help designers, we switched to a portal based
> renderer".
> Isn't placing portals an extra burden on artists? I know BSP just has =
the
> annoying preprocessing, but is there any other reason? It would be
> interesting to know how many FPS games don't use BSP.
>=20
> I assume the portal rendering just for indoor areas since "portal
> technology
> effectively confines us to render interior scenes only" [1].
>=20
> Previously I have used BSP because I read that it is more efficient,
> perhaps
> that is no longer the case? "BSPs trade performance at run-time for a =
slow
> preprocessing step performed when building the world" [1].
>=20
> What I need is a system to draw architectural buildings + their
> surroundings
> for large architectural projects (which have fairly large landscapes). =
I
> have decided to use terrain algs for the terrain, LOD for vegetation =
and
> LOD
> for outside buildings, and either BSP or portal for inside buildings.
>=20
> I suppose I will do both and use whatever seems easiest throughout the
> whole
> development process.
>=20
> The scary thing before was that you had to place portals manually. But =
in
> the buildings I am working with defining where rooms and portals are =
is
> hard. Sometimes there are so many windows and voids you could almost =
say
> there is one room. Do artists still have to manually place portals? I =
know
> that you can do "glass shader" =3D portal, but manually placing the =
rest
> still
> seems like too much work.
>=20
> Do any games use a bsp like algorithm to determine portals for the =
portal
> rendering algorithm? or some other automated portal placement?
>=20
> I read a new paper on portal rendering that works for indoor and =
outdoor
> scenes (well very limited outdoor scenes) called "breaking the walls",
> released this year. It had automatic portal placement that is supposed =
to
> be
> better than the bsp automatic placement of portals.
>=20
> I also read that doom3 uses portals to connect areas. HL2 uses the =
usual
> bsp
> for indoors and some advanced real-time occlusion for outdoors. So I =
guess
> FPS games can successfully use either portals or bsps for their indoor
> parts. And I am still unsure whether I should go the bsp route again =
or
> the
> portal route.
>=20
> [1]
> http://www.medialab.chalmers.se/c2c/doc/portals.html
>=20
> -Ryan De Boer
>=20
>=20
>=20
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