1

I am making a sphere with the radius of earth (6371000 meters). I have only limited zoom out and that makes it impossible to add something on the terrain. If I press F, it does not zoom out further than I could before. I tried to add a very large object like terrain and hitting F, but the zoom was still not sufficient.

I am using Unity 5.2.1

John K
  • 113
  • 6
  • Just out of curiosity, why do you have a sphere that large? If you're trying to model the solar system, just scale everything down. – jhocking Oct 21 '15 at 15:19
  • @jhocking I want to make an Earth's surface just as I would make a terrain. But I want to open the possibility for for instance orbits – John K Oct 21 '15 at 15:44
  • Use different models for close-up and in-orbit. You're obviously not going to model every bit of the Earth's surface (er, I hope you're not) so you'll have to transition between close-up and in-orbit anyway. – jhocking Oct 21 '15 at 16:00
  • 2
    Unity uses single-precision floats for entity positions, which lose precision as the numbers get bigger (no matter what units you use). 1 Earth radius from the origin, this can only specify positions to within a quarter of a metre, which is likely to be too coarse for your gameplay needs. Instead of literally building the whole planet in your scene, you'll want to look for ways you can spawn just the part of the surface you're looking at, close to the scene origin. – DMGregory Oct 21 '15 at 16:06
  • @DMGregory Please put your comment in an answer as it solved my problem – John K Oct 21 '15 at 17:28

1 Answers1

3

As described in my comment above, there's actually a good reason Unity's editor doesn't like to zoom out to these scales, and forcing it to do so is likely to just reveal more problems.

Like many engines, Unity uses single-precision floating point numbers to represent object and vertex positions. Floating point representations can handle an immense range of values, but they lose precision as the numbers get larger.

At 1 Earth radius from the origin, positions can only be specified to a resolution of a quarter of a metre, which is likely to be too coarse for almost all gameplay. (Imagine if your camera was jumping a quarter metre every time you nudged it, or if objects were hovering a quarter metre above the ground because that's the closest non-intersecting point the physics simulation could find)

This doesn't get substantially better if you change units or work in miniature. Changing to 1 unit = 1 km makes the values 1000 times smaller, but an error in the last decimal place matters 1000 times as much, so it basically washes out.

The way this is normally dealt with is to keep the action of the game centred near the origin of the coordinate system (0,0,0), and shifting it back there when the player strays too far away. As long as everything in the world shifts together, the player won't perceive this movement.

This will probably require spawning just the visible parts of the Earth's surface on demand when your player is close to them. (And falling back on a scaled-down sphere proxy when the player is far away)

Since you can't use the editor to assemble the whole planet in your scene view, you'll need to look at other ways of describing what you want on your surface, like...

  • storing it in chunks where each item is close to its local chunk origin
  • generating surface content procedurally on demand
  • storing your level data in a custom file format using higher-precision numbers so you still have precision over planetary scales
Community
  • 1
DMGregory
  • 134,153
  • 22
  • 242
  • 357