First, excuse my English.
I have a problem with mipmapped textures :
-To reduce the number of textures I group them in a big texture.
-The polygons are associated to the little textures with textcoord.
It works well with the following constraints:
-Each little texture may have a width and a height equal to a power of two (for mipmapping).
-Each little texture may be located within the big texture in a subdivision of two (for mipmapping)
-The UV textcoords may describe the relative position of the corners of the little texture within the big texture.
-The UV textcoords may be shifted for half of pixel !!!
If I don’t shift the UV textcoords, polygons use a portion of the neighbouring textures.
This phenomena appears again with mipmapping because the shift is no longer valid :
For a 1024x1024 texture, the shift is 0.5/1024
With mipmapping the texture becomes 64x64 for example and the shift may be 0.5/64.
What can I do ?
For example, how can I precise different UV Textcoord for each mipmapping level ?