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I want to add a small moon and a few stars to the background - or at least behind everything, so that it behaves correctly for camera motion.

  1. Camera rotates around its own axis: moon and stars rotate about center of FOV
  2. Camera pans (rotates around an axis perpendicular to its own axis): moon and stars translate. (if you turn your head, the stars move)
  3. Camera moves (translates in (x, y, z)): moon and stars remain fixed. (if you walk, nearby objects move, but the stars don't)

My animation is technical (think satellite in low earth orbit) so it needs to be fairly accurate. Neil deGrasse Tyson is a major hero of mine. I'll use a normal camera, not orthographic, and I'll use cycles and nodes. I may translate up to 10 blender units and the moon and stars shouldn't move by more than a pixel.

I could make a very very big image and put it very very far away, but is there a better way? I can generate the stars algorithmically if necessary, so that when the camera pans they move correctly.

Can we define a background (e.g. a sky) at infinity? Can we paint (uv map) on to the "Celestial Sphere"? There is some work on Blendertarium (also here) but I'm not sure how to adapt that technique to handle a scene with nearby objects as well.

Edit: After reading @PGmath 's comment, I realized I should also mention that the moon appears to move relative to the stars over time - roughly it's own diameter every hour. So the moon's image would move relative to the point-like stars.

moon and wrong starsmoon moving against stars

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    $\begingroup$ Looks like you want to make a homemade panoramic environment background. $\endgroup$
    – PGmath
    Jan 11, 2016 at 3:21
  • $\begingroup$ Wow, I never would have guessed "panoramic environment background" as a search term - that might work!. I found this answer just now. It would be better if I could put things "on" that. Over the period of a 100 minutes (the communications satellite's orbit around the earth), the moon moves almost twice it's diameter relative to the stars. $\endgroup$
    – uhoh
    Jan 11, 2016 at 3:40
  • $\begingroup$ Constraints? copy the location and rotation of the camera, with 80% influence the sphere would lag behind. Maybe even a transform constraint to turn a camera move into a sphere rotate, or a combination of two or three with small influences. $\endgroup$
    – sambler
    Jan 11, 2016 at 8:01
  • $\begingroup$ @sambler see my comment to the answer below - are you talking about a pair of spheres with a diameter of a few thousand blender units, the "inside" one transparent with an emissive image of a moon, and the outside one black with emissive stars? (a little like this but hopefully not like this)? :) I'm trying to get away from giant spheres and huge distances if possible. $\endgroup$
    – uhoh
    Jan 11, 2016 at 8:19
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    $\begingroup$ I was thinking sphere but constraints or parenting would make it follow the camera so you wouldn't need to have it huge. The size would depend on how many objects you want visible inside it. A moon could be placed on a plane and follow with constraints. Maybe a driver could adjust the background transform. $\endgroup$
    – sambler
    Jan 11, 2016 at 8:57

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You can make a hemisphere or a sphere(depending on what you want). Then, use a particle system on it. Use a material for the stars, and another one for the half dome. Make the half-dome transparent too, so it wont get in the way of the stars.

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  • $\begingroup$ Thanks @WhovianBron3! By "...and put it very very far away, but is there a better way?" I'm really trying to find out if Blender has a way to just put things at (effectively) infinity. This time I may only move 10 blender units, but what If I want to move more - I'd have to keep expanding this sphere. Even now, it would have to be many thousands of blender units - this is not a problem? They would be emissive - would they have to be really really bright? $\endgroup$
    – uhoh
    Jan 11, 2016 at 3:42
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    $\begingroup$ Well the 'Sun' lamp has parallel rays (fake convergence) because you can't have infinite (r extremely huge) distances in Blender. $\endgroup$
    – 3pointedit
    Jan 12, 2018 at 5:21
  • $\begingroup$ Infinite anything is impossible in computers. There is only a max distance computers can handle in 3D space, which depends on both the hardware and software. $\endgroup$
    – WhovianBron3
    Jan 13, 2018 at 6:44

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