RE: [Algorithms] 2d clipping of 3d geometry

[Tom F. <to...@mu...>]

D3DXMatrixPerspectiveOffCenterLH/RH should do what you want.


Tom Forsyth - Muckyfoot bloke and Microsoft MVP.

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> -----Original Message-----
> From: Jason Zisk [mailto:zi...@n-...]
> Sent: 19 May 2003 19:25
> To: gda...@li...
> Subject: Re: [Algorithms] 2d clipping of 3d geometry
> 
> 
> I tried this method, and like others it seems to fall apart 
> if the viewport
> isn't centered on the screen.  As soon as the viewport moves it gets
> seriously warped.  I guess I forgot to mention this was for a portal
> renderer in the original email, sorry if that wasn't clear.  
> :)  Since the
> portal might be anywhere on the screen, the screen-space 
> viewport around it
> could also be anywhere, including with a funky aspect because 
> of the shape
> of the portal.
> 
> I've been trying to figure this one out for a while, it seems 
> like it should
> be doable to set up the projection so its the same as when 
> the viewport is
> fullscreen and just render what is in the viewport like its a window,
> automatically cutting out anything not inside the viewport.  
> But maybe the
> only way to do this is via the scissors stuff in OGL and I'm 
> trying to do
> the impossible?  (Using D3D at least).
> 
> > BTW, if you lay out the depth buffer in the first pass, 
> then all your
> > fancy pixel shader stuff in the following passes will only be
> > calculated for visible fragmets (assuming you don't alter 
> depth in the
> > shader).
> 
> Yeah this may just be the better solution.  It would require 
> one additional
> pass, eating up tons of transform time if the env. is very 
> poly heavy but if
> fillrate is the issue it might end up being a savings.
> 
> - Jason Zisk
> - nFusion Interactive LLC