open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello
I am trying to simulate urban flood and make a grid with bluekenue. I added the city boundary in outline and the building polygon in softlines. After generating the grid, the place with buildings is not hollow as I expected (1 in the figure). Many of the areas that need to be hollowed out are filled with grids (2 in the figure), how do I correctly generate a grid that excludes urban buildings?
Thank you！

It might be that your building soft lines are closed, this could be the issue. From the BK manual... "Open Soft Lines produce breaklines where the node spacing is determined from the density object" this is what seems to be happening in your case. You could always try resampling the lines to your desired mesh density and add them as hardlines.

Hi Barry,

I am 100% sure that this is due to those building outlines not being "closed". ie. first point and last point are coincident.

I would also recommend you follow the suggestion by e.roome to use hard closed lines for the building outlines to more accurately represent the building shapes.

Hope this helps... Martin