Handling Delft3D-Flexible Mesh (triangles & quadrilaterals)

[rsignell-usgs]

@scw, we would like to adapt dap2tin to handle Delft3D-Flexible Mesh, which in addition to triangles, has quads:

Do you seen any issue with just dividing each quad into two triangles?
There is no alternate data type in Arc that would work right?
The objective is to let the Arc user to do the interpolation from data-on-mesh to data-on-raster on demand, to avoid writing rasters that cover the whole domain at the highest resolution of the grid