he number of spatial data
   points (M x N) exceeds 2500 (since such large movies are rendered
   using a technique that does not support interpolation).  However, when
   M x N is less than 2500, interpolation can be used for spatial data
   smoothing.  Note that OpenGL and zbuffer interpolate differently; in
   general, zbuffer interpolates in the colormap and is thus a more
   accurate spatial smoothing.  However, OpenGL may be faster on systems
   where hardware OpenGL acceleration is available.</pre></