[PD] GEM camera angle-of-view >180deg

[Claude Heiland-Allen]

Hi Marian,

I've not tried this, but:

On 14/04/12 17:47, Marian Weger wrote:
>> Is it somehow possible to get a 360 degree angle-of-view with the GEM
>> camera inside a framebuffer?
>
> Isn't there some easy way to do the same thing?

I don't think so.

You could use a vertex shader to implement your own projection 
algorithm[0] to reduce any strange effects from stitching together 
multiple perspective projections.  Perhaps "angular fish eye"[1] for the 
"wide" direction only (modelling a cylinder instead of a sphere).

Almost surely[2] it will still be necessary to render a few wedges of 
the cylinder to get a full 360 without bad problems at the edge cut[3].

An example of a "bad problem" with full 360 wide angle camera: something 
directly opposite the direction of the center of the view gets drawn as 
a huge wide thing that crosses from near far left to near far right 
instead of two small things one that goes from near far left to the far 
left edge and the other that goes from near far right to the far right 
edge.  Little ASCII diagram:

|  <-------------------------------->   |  bad problem
|-->                                <---|  what it should really be


Claude

[0] http://www.google.co.uk/#q=vertex+shader+360+wide+angle+projection+-xbox
[1] http://paulbourke.net/miscellaneous/domefisheye/fisheye/
[2] http://en.wikipedia.org/wiki/Almost_surely
[3] http://en.wikipedia.org/wiki/Branch_point#Branch_cuts