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I've been experimenting with creating lightprobe images for space scenes, using
a combination of GIMP and PoVRay.
The process is pretty straightforward: I begin by creating a space scene as a
cubemap in GIMP, I then import the map as a png into a custom model in povray,
and render using a spherical camera at an aspect ratio of 2:1 (4000x2000) with
output set to +FE.
The only problem I see with my image is that the stars may be a little too
dense, or too large, to be realistic when mapped onto the cube.
The real problem I'm having is that I can't seem to get the EXR image to map
back onto a sphere properly. It's always very distorted.
I've uploaded the relevant files to my dropbox, since they're a bit large for
uploading here. If anybody can tell me what I'm doing wrong, I'd appreciate it.
https://www.dropbox.com/sh/gj5khxb2nqg02kx/AABGsc5rP7PX34sUk3ExJkZFa?dl=0#/
Regards,
A.D.B.
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On 12/21/2014 11:49 PM, Anthony D. Baye wrote:
> I've been experimenting with creating lightprobe images for space scenes, using
> a combination of GIMP and PoVRay.
>
> The process is pretty straightforward: I begin by creating a space scene as a
> cubemap in GIMP, I then import the map as a png into a custom model in povray,
> and render using a spherical camera at an aspect ratio of 2:1 (4000x2000) with
> output set to +FE.
>
> The only problem I see with my image is that the stars may be a little too
> dense, or too large, to be realistic when mapped onto the cube.
>
> The real problem I'm having is that I can't seem to get the EXR image to map
> back onto a sphere properly. It's always very distorted.
>
> I've uploaded the relevant files to my dropbox, since they're a bit large for
> uploading here. If anybody can tell me what I'm doing wrong, I'd appreciate it.
>
> https://www.dropbox.com/sh/gj5khxb2nqg02kx/AABGsc5rP7PX34sUk3ExJkZFa?dl=0#/
>
> Regards,
> A.D.B.
>
>
Why not simply continue using a cube map? Spherical maps usually look
like crap anyway. There's some source code below this image:
http://commons.wikimedia.org/wiki/File:Panorama_cube_map.png
Mike
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> I've been experimenting with creating lightprobe images for space scenes, using
> a combination of GIMP and PoVRay.
>
> The process is pretty straightforward: I begin by creating a space scene as a
> cubemap in GIMP, I then import the map as a png into a custom model in povray,
> and render using a spherical camera at an aspect ratio of 2:1 (4000x2000) with
> output set to +FE.
>
> The only problem I see with my image is that the stars may be a little too
> dense, or too large, to be realistic when mapped onto the cube.
>
> The real problem I'm having is that I can't seem to get the EXR image to map
> back onto a sphere properly. It's always very distorted.
>
> I've uploaded the relevant files to my dropbox, since they're a bit large for
> uploading here. If anybody can tell me what I'm doing wrong, I'd appreciate it.
>
> https://www.dropbox.com/sh/gj5khxb2nqg02kx/AABGsc5rP7PX34sUk3ExJkZFa?dl=0#/
>
> Regards,
> A.D.B.
>
>
As your image is intended to be mapped onto a box, mapping it to a
sphere, using whatever method, can only introduce some distortion,
specialy near the vertices.
Start by UV mapping your image onto box{-1, 1}. Your original image have
exactly the right cross shape for that purpose. The image is intended to
be used with the camera at <0,0,0>.
Scale that box large, something like scale 1000 or more. The exact
scalling depend on the dimention of the scene where you intend to use
your sky.
It's best to place the camera at the origin to prevent introducing
further distortions.
This should take care of any distortion.
As for the stars been to large, you'll need to keep them the same size,
but make the image larger.
Alain
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Alain <kua### [at] videotron ca> wrote:
> > I've been experimenting with creating lightprobe images for space scenes, using
> > a combination of GIMP and PoVRay.
> >
> > The process is pretty straightforward: I begin by creating a space scene as a
> > cubemap in GIMP, I then import the map as a png into a custom model in povray,
> > and render using a spherical camera at an aspect ratio of 2:1 (4000x2000) with
> > output set to +FE.
> >
> > The only problem I see with my image is that the stars may be a little too
> > dense, or too large, to be realistic when mapped onto the cube.
> >
> > The real problem I'm having is that I can't seem to get the EXR image to map
> > back onto a sphere properly. It's always very distorted.
> >
> > I've uploaded the relevant files to my dropbox, since they're a bit large for
> > uploading here. If anybody can tell me what I'm doing wrong, I'd appreciate it.
> >
> > https://www.dropbox.com/sh/gj5khxb2nqg02kx/AABGsc5rP7PX34sUk3ExJkZFa?dl=0#/
> >
> > Regards,
> > A.D.B.
> >
> >
>
> As your image is intended to be mapped onto a box, mapping it to a
> sphere, using whatever method, can only introduce some distortion,
> specialy near the vertices.
>
I figured this was the problem, but it didn't occur to me until long after I'd
posted the question.
> Start by UV mapping your image onto box{-1, 1}. Your original image have
> exactly the right cross shape for that purpose. The image is intended to
> be used with the camera at <0,0,0>.
>
> Scale that box large, something like scale 1000 or more. The exact
> scalling depend on the dimention of the scene where you intend to use
> your sky.
> It's best to place the camera at the origin to prevent introducing
> further distortions.
>
> This should take care of any distortion.
>
> As for the stars been to large, you'll need to keep them the same size,
> but make the image larger.
>
>
> Alain
Thanks for the advice.
Regards,
A.D.B.
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