03-30-2015, 10:54 PM
When adding 3D areas over planar shapes (box, plane) you can add a simple plane above the original object and add semitransparent texture there. But with sphere this is much more complicated because you would need to correctly position the overlay texture with calculating correct texture coordinates.
Therefore I would advise you to solve this problem with converting it to 2D problem - so to change the original texture with "painting" red area to the image. This can be done with using MaterialGroup and adding two textures to the sphere - to have a more predictable results it is best to create the second texture the same size as the first texture and with transparent background and then paint it with red over the "Africa area" (for your example).
You can also change the original texture with adding additional color to it (see internet on how to do that) and use only one changed texture. This probably gives you the most control over the final result.
Therefore I would advise you to solve this problem with converting it to 2D problem - so to change the original texture with "painting" red area to the image. This can be done with using MaterialGroup and adding two textures to the sphere - to have a more predictable results it is best to create the second texture the same size as the first texture and with transparent background and then paint it with red over the "Africa area" (for your example).
You can also change the original texture with adding additional color to it (see internet on how to do that) and use only one changed texture. This probably gives you the most control over the final result.
Andrej Benedik