First you need to prepare your geometry in Rhino. If you don’t already have the geometry of the area you will analyze, one way to acquire 3d urban geometry is to import it from GIS files using the Meerkat plugin for grasshopper. Below are the geometry and what you need to pay attention to while creating them:

  • Buildings: these need to be extrusions of flat polygons on the XY plane. Their base should not sit on top of the topography mesh, but the XY plane, at Z=0.
  • Walls: these are boundaries that you usually have to model manually, unless you already have a detailed GIS file or a 3d model. The walls should be extrusions of line geometry sitting on the XY plane, and not the topography mesh, just like the building geometry. This is why, all boundaries will essentially be modeled like walls, may they be hedges, fences, gates, removable parking barriers or in some cases, parking lots. You should decide if the urban space they separate is accessible or not, and accordingly model the barrier or not. Below are several cases of boundaries that may be modeled as walls.

   

  • The topography mesh: the code only requires topography points (located at their correct elevations). Nevertheless, it is advisable to first create a delaunay mesh and make sure that the top-most vertices of the walls and building geometry remain above the mesh geometry (avoid the case in the image below). Otherwise, the QGIS code will give you an error. If the topography points are not dense enough, you may also get an error in the 3rd QGIS code you are going to run in the next step. If that happens, extrapolate a denser set of topography points. For this, you can project a 10m x 10m grid of points on the delaunay mesh.

By | 2018-05-10T21:36:41+01:00 May 10th, 2018|