In the Generating detailed building footprints from LiDAR recipe in Chapter 4, Working with Vector Data – Advanced Recipes, we explored the automatic generation of building footprints using LiDAR data. What we were attempting to do was create 2D data from 3D data. In this recipe, we attempt the opposite, in a sense. We start with 2D polygons of building footprints and feed them into a function that extrudes them as 3D polygons.
For use in this project, we will extrude a building footprint of our own making. Let us quickly create a table with a single building footprint, for testing purposes, as follows:
CREATE TABLE chp07.simple_building AS SELECT 1 AS gid, ST_MakePolygon(ST_GeomFromText('LINESTRING(0 0,2 0,2 1, 1 1, 1 2, 0 2, 0 0)')) AS the_geom;
Let us add a function from the Improving ST_Polygonize recipe in Chapter 4, Working with Vector Data – Advanced Recipes, that converts geometry collections to multipolygons and add it to this...