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

marius schebella marius.schebella at gmail.com
Wed Oct 17 22:47:37 CEST 2007

hmm... no, I don't know how to do it. with gem you can only do 
rectangular projection/texturing. so you would have to find a way to 
distort the texture so that it will be displayed correctly on one half 
of the sphere. you probably need some vertex shader to do that...

Alex wrote:
> so to make this easy think of a square texture that has a picture the
> globe centered inside it.
> i want to take that picture and map the flat image of the globe onto a
> hemisphere so that you see [in this virtual world] 1/2 of a globe,
> warped so that, in the virtual world, it looks correct.
> -Alex
> On 10/15/07, marius schebella <marius.schebella at gmail.com> wrote:
>> 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.
>> marius.
>> 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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