RE: [Algorithms] Clipping to reflection plane (Was: Re: water reflection)

[Tom F. <tom...@bl...>]

I think the problem is that oblique angles happen all the time. In games
we tend to look horizontally. Reflective surfaces tend to also be
horizontal (water, puddles, polished floors, etc). Result - aliasing
hell as all the pixels bunch up against one else of your rendering
frustum.

TomF.

> -----Original Message-----
> From: gda...@li... 
> [mailto:gda...@li...] On 
> Behalf Of Jon Watte
> Sent: 10 July 2003 17:33
> To: gda...@li...
> Subject: RE: [Algorithms] Clipping to reflection plane (Was: 
> Re: water reflection)
> 
> 
> 
> > While we are at it, allegedly, there is a way to adjust the 
> > perspective matrix in such way that the
> > standard view volume clipping will in fact clip to your 
> > reflection clip plane.
> 
> That's exactly the other case I was describing; here's how I 
> understand it 
> to be done:
> 
> You treat the intersection of the water surface and the 
> viewing frustum 
> as your "render target" and set up a projection that maps 
> this very un-square 
> area in world space to the rectangular render target. The 
> perspective divide 
> should set it up so that you get your "near" value at the 
> point where the 
> ray hits the water surface/render target. (This is from the 
> point of view of 
> the camera, which is at the reflected camera pos, underneath 
> the water).
> 
> Once all that's done, the near clipping plane will be the 
> water surface, and 
> everything above it will render; what's below it, will not. 
> Watch out for 
> aliasing with oblique angles!
> 
> Cheers,
> 
> 			/ h+
> 
> 
> 
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