[PD] texturing a circular image onto a hemisphere in GEM

marius schebella marius.schebella at gmail.com
Tue Oct 16 02:47:33 CEST 2007

Hi alex,
I am not sure what you're trying to do, but I am eager to help you...
do you want to project the video onto a wall/ceiling hemisphere inside a 
real room? or are you talking about virtual projections?
I guess what you have to do first is distort the circled video back into 
a square and then use that to texture the sphere.

sphere with a ? is it just the mapping on the spherefor any distortion you

Alex wrote:
> Maybe a different subject will inspire some help?
> basically, I have video that was shot on a mirrored spherical ball..
> this gives a circular image inside a rectangular video, I've figured
> out how to crop it so that I just get the square that surrounds the
> circle, but I cannot figure out how to correctly map this texture onto
> a sphere so that it is only on one hemisphere and so that the circle's
> circumference is on a "great circle" of the sphere? [ie it the circle
> is warped out so that it becomes a hemisphere].
> I figure maybe I have to do some GEMgl stuff for this?
> if anyone has done this, would you please share?
> If not, any advice?
> Thanks,
> -Alex
> On 10/10/07, Alex <x37v.alex at gmail.com> wrote:
>> I have some panoramic video that I want to use to texture a hemisphere
>> [or rather, the bottom half of a sphere].
>> I cannot simply texture the sphere with the video because the warping
>> is not correct.. it seems that I need some sort of non-rectangular
>> warping of the image before I texture the object, or a non-rectangular
>> mapping of the texture onto the sphere.
>> Any ideas or advice?  Does anyone else have experience working with
>> panoramic video in Gem?
>> -Alex
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