From: Benedikt Kessler (bjk++at++munich.sgi.com)
Date: 11/10/2004 01:38:25
Hi,
rick.van.haasen++at++philips.com wrote:
>
> Hi
>
> i have problems using a pfEarthSky on channels with an asymmetric
> perspective viewing frustum:
That is a known problem and documented in the manpages:
NOTES
pfEarthSky does not work properly for off-axis viewing frusta.
>
> My application uses 5 channels. These channels are used to compose 1 wide
> screen using 5 projectors.
> For this setup each channel needs a unique viewing frustum definition (in
> order to keep "straight lines straight").
> So far so good. However, when i use a pfEarthSky for these channels, only
> the "middle"
> channel (this is the only one that has a symmetrical viewing frustum)
> displays correctly, the other 4 don't,
> with areas not being cleared at all, showing accumulated data from
> previously drawn frames.
> I also see that the "incorrectness" is dependent on the the far clipping
> plane distance.
>
> It seems to me that the method used for clearing the background with
> earthsky-data doesn't work correcly
> if the viewing frustum is "skewed". I looks somehow as if the "screen
> filling earthsky-quad" that should be
> rendered just in front of the far-clipping plane is not propperly aligned
> to the far-clipping plane of the skewed
> frustum.
>
> Is there a solution for this problem?
Either use PFES_FAST for PFES_BUFFER_CLEAR mode. Of course you wont get the shared sky nor the ground...
Or replace that simple earthSky model by your own model (or channel draw callback). I liked to get different sky shading depending on the time date, position on earth view direction (the simple earth sky shows you the same shading whether you look to the
north, south, west or east).
Bye! Benedikt
-- +---------------------------------+----------------------------------+ |Benedikt J. Kessler | Silicon Graphics GmbH | |Advanced Media Products | Am Hochacker 3 - Technopark | |SGI | 85630 Grasbrunn-Neukeferloh, FRG | | --- __o ,__o | | | ------_ \<,_ _-\_<, | Phone: (+49) 89 46108-366 or -0 | |----- (*)/ (*) (*)/'(*) | Fax: (+49) 89 46107-366 | +---------------------------------+----------------------------------+ |E-Mail: bjk++at++sgi.com Web (private): http://sgiweb.org/bjk | | Web: http://www.sgi.de | +--------------------------------------------------------------------+
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