Re: Heat hazes

["Adam D. Moss" <adam@gimp.org>]

Katie Lucas wrote:
> I've been playing "Jak and Daxter" on the PS2 recently, and there's
> this very nice effect with heat hazes rising from torches and
> things. The PS2 is structured around OpenGL,

I wish it were true that the PS2 is structured around OpenGL!
Is it, indeed?

> so it may be an OpenGL
> effect - any ideas how it's done?
> I can think how to do it with a per-pixel texture processor (look at
> the existing image and distort it, but is there a reasonably fast way
> without that?

Without having seen it firsthand, the way I imagine it's done is that
the scene is drawn approximately back-to-front and that when it comes
to render the torch the 'behind the torch' framebuffer contents are
sucked into a texture (PS2 has pretty fast paths for fb->texture
and render-to-texture) and drawn as a billboarded mesh with its
vertices wiggled.

Another possibly-nicer way would be simply to set up a vertex
program to wiggle the vertices a little in the volume behind the
torch from the eye's point of view.

--Adam
-- 
Adam D. Moss   . ,,^^   adam@gimp.org   http://www.foxbox.org/   co:3