night sky cubemaps with stars

[mecha]

has anyone had any luck using "starfield" images applied to the background when rendering out cubemaps or panoramas?

[Henry Blewer]

In your Objects Group.  Right-click on it and go the internal network.  There is where you can add a Default Shader, then add other images, etc.  Click this Default Shader into your Background and VOILA...a new world of lighting.  Tweaking with the other values and then messing with the GI configuration can even eliminate the need for a sun object.

Whats the background shader?

This might help. The Background shader determines color or the image used behind all the 3D stuff.

[rcallicotte]

To add to njeneb's accurate description, you can use the Background Object to affect lighting as well.

[cyphyr]

You might also want to check out Seths procedural night sky

link

Richard

[shadowphile]

I've been searching for an accurate HDR night sky image with no luck.
I've read arguments about how HDR is wasted on a night sky, but that is baloney!  Reflections and real stars will streak appropriately in animations, atmospheric twinkle and bloom will perform correctly, zooms into the starfield will not blowup pixels unnecessarily...

This is the closest I have found, still might be useful to you. 
http://svs.gsfc.nasa.gov/goto?3572

The main problem is that the brighter stars have been widened for perceptual effectiveness, making the brightest star almost as wide as the moon in some cases!  There are several resolutions and brightness levels, so you might still find it useful.
I actually emailed the creators and made an argument for a more realistic HDR version with no point-spread-function for CGI developers.  Not surprisingly I didn't get a response.    
...Hey, maybe if the other users here blitz them...

[cyphyr]

I think that HDR is indeed wasted on images at night. However you should be able to get good reflections under the right circumstances. The trouble is that HRD is calculated as an approximation. An image, mostly black with small pin pricks of light will cause most renderes (not just TG2) into highly forces approximations. You'll get massive grain and noise unless you turn up the quality settings, (possibly the GI detail and quality as well) to obscene levels. It will take an eternity to render. THe images you ;link to could provide great backdrop starfields but will not illuminate your image in any meaningful way.

Richard

[Henry Blewer]

I have found this software fun and the sky maps can easily be 'grabbed' for use elsewhere.
http://www.stellarium.org/
It's a planetarium sim. Looks great.

[Kadri]

I actually emailed the creators and made an argument for a more realistic HDR version with no point-spread-function for CGI developers.  Not surprisingly I didn't get a response.    
...Hey, maybe if the other users here blitz them...

İ am still downloading these files so i might be totally wrong.But i thing there are HDR programs to make a HDR file from a series from pictures.İf these 3 (?) files are appropriate then you can make a so so  HDR file for yourself.Just a thought.

İt may be useful for you to Mecha.

Kadri.

[shadowphile]

cypher: Although I agree they are useless for illumination purposes, I've had good success with all the reasons I stated using (faked) HDR starmaps in Blender (which doesn't have the 'detail' slider that exists in TG). I might be wrong about how useful they are in TG.

Kadri: the problem with the pics is that they are not based on exposure but on magnitude threshold, which is a non-linear illumination function that amplifies the dimmest stars to make them more visible in low-dynamic range images. (or dims the brightest stars, not sure which
In addition, stars in reality are virtually point sources, which is how they would be represented in an HDR file. (might be an argument for some multi-pixel stars).  But because the NASA pics were meant to be just looked at, they applied a point-spread function ('PSF') that blossoms the stars out based on how bright they are, to make them appear 'brighter' to the eye.
There is a way to inverse the point-spread function to collect those spreads and shove them back into a pixel with appropriately high brightness values (beyond what a jpg can handle) but that is very difficult guesswork if the original PSF is not known.

njeneb: thanks for the link, for general backdrops this program looks interesting.

[Henry Blewer]

You can turn off everything except the stars and nebula. I've used screengrabs from this program. I also you Stellarium when I get a 'star longing'. The light pollution here in Binghamton makes it impossible to see any.

[Kadri]

...
There is a way to inverse the point-spread function to collect those spreads and shove them back into a pixel with appropriately high brightness values (beyond what a jpg can handle) but that is very difficult guesswork if the original PSF is not known.
...

i see 
İf you use Lightwave there are this plugin http://www.maasdigital.com/starpro/   
i haven't used it.There is a chance it may useful . İf you can the output bring to HDR. İt is pricy but it has a demo.
There are maybe plugins for the other 3D programs.

Kadri

[mecha]

thanks guys, this is all good info, and i suspect all of these solutions will work just fine in a panorama render. I've also been playing with using 3d Studio Max's "starfield" post effect renderer, to render out the milky-way + random starmaps.

[cyphyr]

This might be useful to you :

The first of three images unveiled for ESO's GIGAGALAXY ZOOM project is a magnificent, 800-million-pixel, 360-degree panoramic image that covers the entire southern and northern celestial sphere and reveals the cosmic landscape surrounding our tiny blue planet...
..
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This magnificent 360-degree panoramic image, covering the entire southern and northern celestial sphere, reveals the cosmic landscape that surrounds our tiny blue planet. This gorgeous starscape serves as the first of three extremely high-resolution images featured in the GigaGalaxy Zoom project, launched by ESO within the...

link
Images Highres image is available in the box to the right of the page
The full res image is available from the author by request.

Hope this is useful
Richard

Did a quick render using an old scene. Added the highest rez "Galaxy Map" (6000px x 3000px) to the background object (default shader with an image map shader plugged into the colour and luminosity channel). Well the results speak for them selves, not really good enough but it shows that a higher resolution image, were it made available, I think could work very well