I have a 3D LiDAR data and aerial images.
Is there a way to obtain the buildings multipatch (.shp), given that I don't actually have the buildings' footprints?
One way to do this in ArcGIS Pro is outlined in the Extract Roof Forms for Municipal Development tutorial where:
Your goal is to create a 3D scene of an area in Portland with LOD 2 buildings. With the aid of an ArcGIS Pro task, you'll create a point cloud dataset derived from lidar data and use it to make digital elevation models of the area. Using tools that analyze patterns in the elevation models, you'll add roof form attribute data to building footprints and symbolize the footprints in 3D. Lastly, you'll review the data and edit building features to fix errors before converting the data to a multipatch feature class that you can easily share with the municipal government.