I believe that changing the mesh reduced size image also requires a set of images that are also reduced in size. Here is an excerpt from OpenGL Programming Fuid, 2nd Edition, OpenGL Architecture Review Board, Addison-Wesley, 1998.
Thanks a lot,
just resolved the whole issue of slow rendering with big textures, it appears that the mipmap pyramid is not created automatically when calling OpenGL.glTexParameteri (OpenGL.GL_TEXTURE_2D, OpenGL.GL_GENERATE_MIPMAP, opengl.GL_TRUE)
To create the differet mipmap level, glTexImage2d must be called at least two times,
one for maximum resolution (level 0) and one for another generic level N, e.g.: