3D model for filming
The 3D model is the perfect reference boundary between the real and the virtual scene. Most directors prefer real sets, but this is not always enough. The best results are usually achieved with the perfect combination of real and virtual backgrounds and effects.
Later, by creating the 3D models and adding effects, VFX professionals create the illusion that the viewer cannot tell what is real and what is virtual.
Digital terrain model
The digital terrain model is used for big scenes – it may sound strange, but the biggest battle scenes usually have no more than 300 extras, yet the viewer sees tens of thousands of fighters smashing into each other’s weapons
The trick is to replicate these hundreds of virtual actors and scatter them over the terrain to create a dense crowd effect. To give a realistic impression of people walking on real land, every little rock must be in place.