You could try what we do.
The roads and foot paths are slabs that are sited above the mesh.
we then to a 'plan' render in lightworks.
This gives you a jpg file of the roading layout.
Next, create a new material with the render image to drape over the mesh.
his way, it is easy and quick to update (just re save the rendered image over the old one) and there is no calculation required for the SEO's.
This allows us to build up 3D models to fly around with our clients live over fairly big sites.
Cheers,
Karl.
Cheers,
Karl Barker.
27" iMac 3.6 Ghz Intel Core i9
32 Gig Ram
Mac OSX 10.14.6
AC 5.5 - AC22 (NZE)