Using the Delaunay WPS grid, the final map cuts just to the roadside as the following image. The main envelope should take into account the maximum propagation distance and add a buffer around the roads.
The final division of the domain is left to the user's discretion. I think it's rather the Create_Isosurface script that needs to be modified in order to specify a stencil.
Using the Delaunay WPS grid, the final map cuts just to the roadside as the following image. The main envelope should take into account the maximum propagation distance and add a buffer around the roads.