Axes with units and scales + overlaid polygons in visualisations

[ole]

This request is from Rosh Ranasinghe (DNR).

Axes would allow better interpretation of simulation outputs. This could either be implemented in the swollen viewer or the new VTK viewer.

Being able to overlay polygons in the visualisation will allow easy reference to e.g. coastline.

[jack]

Axes support has been committed, polygon overlays are pending. In future requests like these should be two separate tickets. See the examples/sww_file_visualiser_example.py to see how the axes are added.

Caveat: the Z bounds for the axes are computed using the quantity values of the quantities being rendered, after the scaling and offset has been applied? Should this be changed?

There are problems with either method:

• If you use the quantity values before adjustment, it's not good because the box doesn't encompass the visualisation.
• If you use the quantity values after adjustment, the readings for the quantity heights are misleading.

Comments either way welcome.

[jack]

Now added. A list of points can be used to bound a polygon. See the docstring in anuga_core/source/anuga/visualiser/visualiser.py.