[Algorithms] R: Re: One pass per light + transparency?

[Madoc E. <tm...@ti...>]

I've been using this for many years now and I can't say we've ever 
noticed any problems (and we've had burning forests with plenty of 
smoke, and some windows too). I always draw the 2-pass (antialiased) 
"billboards" before any other alpha blended stuff so the worst case is 
that alpha blended stuff behind the billboards (significantly?) reduces 
the AA effect. The biggest difficulty we had was producing a good ratio 
of opaque to blended pixels in the alpha maps, especially throughout 
the mip-map chain. That can be tricky, and affects visual quality 
regardless of other blended geometry.

-Madoc



----Messaggio 
originale----
Da: tom...@ee...
Data: 15-lug-2006 
7.57 AM
A: "Game Development Algorithms"<gdalgorithms-list@lists.
sourceforge.net>
Ogg: Re: [Algorithms] One pass per light + 
transparency?

You use a SRC_ALPHA:ONE pass for passes after the first 
one.

Actually, what you do is use premultiplied alpha, as that is the 
One True
Translucency Blend Method. So the first pass is ONE:
INVSRCALPHA and
subsequent passes are ONE:ONE. They discovered this in 
the 80s, and then
everybody immediately forgot it and kept on using 
SRCALPHA:INVSRCALPHA for
another quarter century. And probably beyond.

TomF.

> -----Original Message-----
> From: gdalgorithms-list-
bo...@li... 
> [mailto:gdalgorithms-list-
bo...@li...] On 
> Behalf Of Brad_Byrd@playstation.
sony.com
> Sent: 14 July 2006 12:12
> To: Game Development Algorithms
> 
Subject: [Algorithms] One pass per light + transparency?
> 
> 
> So 
it's pretty easy to understand the "ambient/z pass, then 
> one pass 
per 
> light" style of rendering popularized by Doom 3.  However, as 
> 
the blend 
> unit is already in use for doing an additive blend for the 
lighting, 
> regular (src_alpha, inv_src_alpha) style transparency is 
> tricky.  I tried 
> googling for this, but was unable to find a 
solution for this 
> problem.  I 
> just found several people saying, 
"Yeah, transparency is 
> tricky...", then 
> not explaining how to 
solve it.  So, what approaches are 
> people taking?
> 
> Also, is 
there a general solution to this problem that would 
> support more 
> 
blending modes than just (src_alpha, inv_src_alpha)?
> 
> Thanks!
> 
> 
Brad...
> 
> 
> 
> 
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Get stuff done quickly with pre-integrated technology to make 
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Download IBM WebSphere Application Server v.1.0.1 based 
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http://sel.as-us.falkag.net/sel?
cmd=lnk&kid=120709&bid=263057&dat=121642
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