...
Refer to the photo below.
1. Simple Extruded Shapes
2. 3D Model - Lives in a separate layer to the map
...
When not to use 3D models
1. When it is possible to use Extruded Shapes - for example when a building has no real architectural features that can't be replicated by simple extruded shapes
2. If it requires too many models. For example you decide to add some trees along a walkway and then realise you need to add the trees everywhere
Things to consider
Colouring the 3D model should consider the surrounding environment. You want to avoid using too many textures and colours, especially with architectural buildings. They should blend in to the environment and not conflict with ‘Extruded Shapes’
Textures on a model may be required for promotional items
Vegetation usually requires multiple models, although there is a maximum size of 1mb for a model, the file size should be kept at a minimum when possible. (e.g. small tree was 6kb)
Models should MATCH each other
The more models you add the more computational power you need to render. Therefore if you decide to add ALL the vegetation to make it realistic, it may require hundreds of 3D models and performance could be compromised
Generally remove any detail in a model that is not required. For example in an architectural building, you only require the outer shell
...