Texture "curvature".

[Lilleman]

Hello everyone!

I'm currently coding something to generate random planet textures at runtime in KSP.

So far, so good, the main problem is, textures are meant to be used on flat surfaces, and need to be distorded at the poles.

Is anyone aware of an algorithm to do this? Computation speed is not an issue.

Thanks in advance!

[Van Disaster]

Rather than curve the texture, unroll the sphere onto it like it's a map - cartographers have been doing this for centuries, so there's a lot of methods. That'll make the texel size uneven across the planet but there's no really easy way around that.

[InsaneDruid]

At least on the navball, squad used an equirectangular projection during uv mapping. So its rather likely they did it on the planets, too, especially as the equirectangular projection gives the distortion in width of texture vs width of area covered by the texture when moving from the equator to the poles.

So it depends from where your internal data model starts. If you starting with a sperical model on where you generate yur data you have to apply an equirectangular projection. If you generating data directly on a plane than you need something of a negative equirectangular projection. (or nothing at all if you can live with the fact that the generated data will be a bit distorted on the poles.)

Edited October 28, 2015 by InsaneDruid

[Lilleman]

Thanks. Textures are generated for a plane shape, so I need to distord them as a "second pass".

Note that textures are created by a fragment shader, and converted to a texture2D via a rendertexture. I can probably write it to map the texture to a sphere directly, but I'm not that good with shaders yet.

If I trust this website http://paulbourke.net/geometry/transformationprojection/ , the solution is to "simply use the polar angles directly as the horizontal and vertical coordinates".

Doesn't seems too complicated, I'll see how it turns out.