   Drawing shapes on a sphere
  Hi all, I'm a programmer but I don't have a lot of experience in 3D programming. I'm looking for a way to draw surfaces over a sphere, using Opengl. Let me explain. My program displays the Earth, which is actually a sphere with textures. I would like to draw regions on its surface, which can be circles or complex surfaces on the ground, filled by a transparent color. These surfaces must match the Earth curvature. Actually, in input I have some points coordinates which describe the contour line, and I have to draw the filled shape, even if I'm not exactly very next to the surface of the earth.My shapes are simpler than that, but it looks like this screenshot, imagine that the USA take any form, a circle or whatever. (this is a STK screenshot)  I'm thinking of different ways to do this :- textures on the earth : why not, but I have a lot regions, sometimes overlapping, or with changing shape in time.- create a mesh with my contour line, and generate NURBS ,Bezier surface, surface patch, or whatever approximating the surface of the earth (tricky?)That's it, do you have any idea of what is done in game or industrial developing for such a feature?Thanks in advance,Kalos.PS: excuse my english, if it's hard to understand i'll give some explanations.   
  I suppose that you could draw your shapes on a texture (either the same where you have the primary image or another using alpha) and then map it onto the sphere.You can then update the texture when you need it. I don't see any reason to do something different, honestly...   ;  Dou you think I can generate my texture at each frame if my shape is dynamic, and give it to Opengl to render it smoothly? The other question is the pole deformation, if I draw next to a pole, even if I respect the spherical projection, will it be... pretty, clean? Well, I'll do some tests if I can.   ;Quote:Original post by kalosThe other question is the pole deformation, if I draw next to a pole, even if I respect the spherical projection, will it be... pretty, clean? Well, I'll do some tests if I can.One way around this is to use a different texture mapping scheme, e.g., cube mapping.At the extreme, you can map to an icosahedron like Fuller did for his "Dymaxion" projection, but I'm not really suggesting this seriously.  Cube mapping is tons simpler.In general, the more "pieces" you split your sphere into for texture mapping purposes, the less distortion there will be.   ;  Thank you for this idea, I'll do some research on the different ways to map a sphere.Thanks to both of you, I have things to do before making some experiment but I'll come back if I have any questions.Cheers.