I am building a 3d topview game like GTA2. In this game the ground is mostly one level (except for tunnels and highways). Most of the ground is also city so the ground is usually covered by either roads or buildings. The buildings are simple 3d models which the player can walk around on. Most of the gameplay is 2d.

How should I model the map? I have considered the following options:

• Bitmaps, I think this gives problems when I want to add data smaller than a tile. Also the problem of bridges and tunnels seems hard to solve with this.

• Polygons, define all roads, terrain types, buildings with polygons and save that along with physics and texture information.

What approach would you take or have you ever implemented this or know of an implementation?