Temp MIP commit to copy to laptop
Fix transform and depth issues for correct MIP render
Fix mip in parallel, LOD not working though
Fix MPI compile error on linux
Leave background colour alone - was grey for debug purposes
Remove unused params from Mip display and rename to avoid conflicts with splotch display
Add support for MIP of multi-component fileds such as velocity
Use Reduce instead of AllReduce for final summation.

Disable use of active array until bug resolved
Improve binding of scalars to controls in panel. remove obsolete vars.

Remove a lot of code copied across from splotch mapper.
Use Combo Domains to map scalar selections to GUI controls and allow them
to pick up default values.
Trying new painter based render
Painter was not mapping scalars properly. Fixed.
Reorganise the MIP code to use a Painter Chain rather than a Mapper.

Fix an issue with ImageReductionFactor when the subsample rate>1
We need to intercept/fetch some values from IceT which is not clean
but no other way is yet obvious.
Add ComputeBounds to ensure screenspace composite covers entire dataset

Clean up view+matrix code using IceT vars and fix a segfault on 1 process.

Remove all Composite Painter/Render from the painter chain and Mappers so that
we only render single datasets and handle bounds nicely.
DefaultPainter allocates MIP painter for convenience
Use IceT sizes when creating images
Fix blocked MPI when one process has no input
Add OpenMP support to MIP renderer
Improve render speed by using unsigned char and experiment with LUT mapping
Fix blank render problem for certain datasets/colours.

Because MIP handles the colour mapping specially, sometimes the ScalarsToColorsPainter
was generating colour arrays with unnamed RGB arrays and not passing through the original
point arrays. We fix this by bypassing the ScalarsToColorsPainter completely from the painter chain
and manually triggering a colortable build before mapping values through.
committed left over (unfinished?) Work on Scalars to Colors