Bump-map a sphere with a texture map

Question

We would like to bump-map a sphere with a texture map. However, the surface of the sphere has an area that is 10 times the area of the texture map(area for both in pixels). Describe different ways in which the texture map can be used for bump mapping.

Answer 1

1. usually rectangle texture is used for spheres

   texture (u,v) coordinates are used as angles for spherical coordinates. The result is that texels are bigger near equator and smaller near poles. At poles all the texels merge to single pixel. This is how to do it

   • texturing spheres
   • normal/bump mapping

   When you use these maps (color,normal,light,clouds):

   
   
   
   

   when combined with single light source (Sun) I got this result:

   

   On the left side with atmospheric scattering and on the right without it. If you zoom a bit you can see the mountains.

2. There are more ways then just rectangular sphere maps

   You can use non linear sphere maps with different properties like eqisurface/distance etc. Here some examples of sphere maps (from google):

   rectangular:

   

   equidistant/paper model:

   

   equidistant: