Planet scale terrain?

[Jovin]

Hi there, I was wondering if it was possible to produce planet scale maps in L3DT. I certainly wouldn't want to have tremendous detail here, I'd primarily be interested in the map output.

[Aaron]

Hi Jovin,

L3DT has been used to make planetary-scale terrain in the past (see the entry for Aaron Pollyea on the users' projects page). The usual problems are:

• Mapping the heightfield/texture to a planetary sphere causes nasty distortions (L3DT doesn't do this either; you have to find another app for that, such as Celestia.)
• Unless you're willing to make a massive (gigabytes) map for your planet, you'll have to make a very low-res map (km's per pixel). The problem here is that the climates in L3DT are not set up for making low-resolution textures (quite the opposite, in fact), so they won't look realistic.
• The design map auto-generator is also not tweaked-up for making low-res maps, so you'll probably have to go in for a bit of manual design map editing.
• Wrapping is also a problem if you want to cover a whole planet, since you need east/west wrapping but not north-south wrapping. L3DT can wrap neither or both, but not either individually.
• Lighting is also a bit strange, since L3DT doesn't do spherical terrain mapping for lighting, the entire planet will be lit all the way around (no occlusion of the dark side). To do this, you'll need to do your light-mapping in a program designed for spherical objects.

So if I can summarise: planets are very difficult, low-res large maps are problematic, and high-res large maps are ideal (the latter is the bread and butter for L3DT).

Cheerio,
Aaron.

[Jovin]

Thanks for the info! That all makes sense to me. I suspected planet scale maps for wrapping 3D spheres to be rather outside of the essential focus for L3DT, as it really is for just about any software, currently. No worries on the spherical mapping concerns, I can get decent spherical maps from Photoshop's filters, and I may have one or two other ways to do this, have to test before I know.

Mainly I just curious, as I've been playing with all my terrain software looking for methods of obtaining planetary distribution/mask maps. Current fix of mine.

Cheers

[Madcowthomas]

If I recall you can do sphere wrapping in Leveller and other various things.

[Jovin]

I have Leveller, so I'll definitely take a look at at that. I was interested in leveraging L3DT's design workflow for planetscale features. I'll keep playing around.

[JohnJ]

I just thought I'd mention that in games, planets are almost never rendered/mapped using a longitude/latitude method, as most modelers do. This always leads to severe distortion in texture and geometry near the north/south poles:


Instead, a cube-mapped approach is used. Obviously, you can easily apply textures and heightmaps to a cube like this:


All you have to do is warp it a little to make it round:


As you can see, there is little, if any, distortion around the seams of each cube face.


P.S. Did you see the siggraph video on how Spore's terrains are generated procedurally? Some of them look really nice (not quite as realistic (more variety though) as L3DT's, but very impressive considering they need to be generated in a few seconds).

Click here to watch.

Note: Siggraph videos are free now only for a limited time, so watch 'em now if you can

[Jovin]

Interesting! I kinda liked the "Little Prince"-esque planets they'd come up with, looks like the cube mapping can pull off seamless sphere textures without glaring pinching, etc. Nifty.

I find it a little easier to pre-visualize a spherically mapped texture, it's a bit more natural to me, and will probably prefer to work with a normal or spherical texture through an editing workflow. When it comes to rendering output, I can definitely see the value of a cube mapped texture for RT rendering in something.

With regard to L3DT and planet scale terrain leveraging it's feature set, I think it's tiling (EDIT: and masking?) to the rescue here; with a bit more time and effort involved in producing a coherent, seamless, tile set (actually, probably a fair amount more). That's fine, it's the same kind of assumption I'd have going into WM2.0 or the like, from the sounds of it.

Aaron, if one were to actually attempt creating a planetary scale tile set from L3DT, , what's the maximum(-ish?) Heightfield resolution (m) value that you'd recommend not surpassing for the design maps? EDIT: With the express intent here of not scaling out of the usable range of L3DT's parameters that is .. any and all performance concerns aside.

Cheers!