Building Coverage Ration and Floor Area Ratio

1.  Basic UV projection

2. Unwrap UV mapping. Please ignore the first half.

Optimize Rhino before export to FBX.

The same rules apply to playcanvas, unity or any other real-time rendering engines. 

using “ungroup, explode, purge, joint, extracrendermesh, and reducemesh”. exercise file download: Rhinoclean

Step 2. Transfer a building model

Note: Please join your building objects in GH or use the “join” command in Rhino before you export to Unreal. You do NOT want to have hundreds of small objects, each saved as an separate files in Unreal, or playcanvas.

Rhino subD modeling: 

multipipe
Gumball + control+shift
Window selection vs double click ( point, edge, face)
Edge loop
bevel
Extrude + Gumball
Reflection
Bridge/stitch
Subdiv
Delete face/edge
crease/hard edge

cage-like structure. 

A similar approach can be found in remesh and retopology. You might also apply a similar method in Revit using Rhino inside Revit, or use Freeform modeling in Max .