   Planet rendering - Storing data & chunked terrain...
  So ive been reading a lot of planetary rendering articles, I think I understand the basics, but there are a couple things that I still dont get...1.) While its easy to wrap textures/height fields to a cube, the geometry itself gets very distorted when turning it all into a sphere. One article I read...http://www.organicvectory.com/planet/planet_index.html...suggested using a  icosahedron, but now how am I supposed to implement my textures/heightmap? I DONT want this to be a procedural planet (I want artists to have control over the shape/textures).2.) Are there any articles that suggest a more 'chunked' approach to planetary rendering? Everything ive read seems very 'roamy', which just doesnt seem as efficient as chunked terrain.Thanks for any advice!   
  *and btw, has anyone seen this paper..http://i31www.ira.uka.de/publikationen/files/4_Studproject_JWinzen.pdfI really like it a lot. Starting with a cube makes it so easy to texture and set up your 'data' (height, object placement, ect...). Im a little concerned about the distortion from cube to sphere transformations though (in my tests it was very noticeable..)   ;  You can't expect get good results from drawing square heightmaps in a paint program or even a square heightmap editor and then distorting them into a sphere. You'll need to either write or find a specialized tool to make them (I think something like Zbrush could be adapted to this). In a proper tool, the sphere should appear as a continuous spherical surface and the artist should not be able to tell how it was created. The advantage of an icosahedron is that it's possible to map each face into a triangular region of a texture that results in minimal distortion from viewing the texture in photoshop to viewing it in game. But it's still difficult for an artist to create the textures without special tools because they have to match the neighboring triangles on the edges. This matching is easier if you map pairs of icosahedron faces diagonally onto a square texture (it becomes as "easy" as the cube, since the seams are along the edges of the texture) at the cost of more distortion. This distortion may still be aesthetically more acceptable than what you get with cubes.   ;  Wouldnt a octahedron work just as well? http://local.wasp.uwa.edu.au/~pbourke/geometry/platonic/Its also made up of equilateral triangles. Seems like it would be easier to adapt a quadtree/chunked approach to something like that..   ;  I just found some links for you. I would explain but the articles probably would do it better. You do know though that what you are attempting is going to take some serious storage and you will need texture paging. Basicly you can break the planet down into a quadtree structure so it is an x sided shape and link texture to it (Which will need to be slightly larger than the dimensions of the quad). Within those parts you could sphere correct the texture coords if the chunk is large. http://www.gamedev.net/community/forums/topic.asp?topic_id=149108Ysaneya has developed an engine that works on Chunk-based LOD, which should be pretty close to what you are after.I can remember seeing an article on using geomipmaps, geoclipmaps or chunklod to render planets which would help you, but i cant find it again.   ;  Thanks, however I read that one already. Unfortunately its pretty old and there was never any follow up (part 2) :(.Im actually starting to lean towards a tetrahedron, since like a icosahedron it is made up of equilateral triangles, and it has 'square' faces (if you combine to triangles). It seems like that would work best for a quadtree approach eh?   ;  One way to gauge the amount of distortion caused by "spherizing" a shape is by comparing the corner angles of the faces before and after the shape was inflated into a sphere. The "after" angle can be calculated by dividing 360 by the number of faces that meet at each corner.For example, cube faces have 90 degree corners that become 120 degrees (33% difference) when you turn the cube into a sphere. Tetrahedron is the worst choice as far as distortion is concerned; 60 degree corners become 120 degrees (100% difference). In an icosahedron, the corner angle of each triangular face only changes from 60 degrees to 72 (20%). In an octahedron, the difference is 50%.Any triangle-faced polyhedron can be further split with a quadtree type structure.   