For the experimental texture volume drawing, changed the texture...

For the experimental texture volume drawing, changed the texture 'magnification filter' to GL_NEAREST.  When zoomed in on a slice, the drawing is much like the current cubic interpolation drawing.  The different is when the volume slice is rotated.  The interpolated drawing draws voxels whose edges horizontal and vertical (aligned with screen axes).  Whereas, in texture drawing the voxel edges are aligned with the stereotaxic axes and thus the voxels edges rotate with the slice rotations.