Tessellation
Letting the GPU subdivide coarse surfaces into many small triangles, driven by a factor that usually shrinks with distance.
The idea is to send a few control points to the card and let a dedicated pipeline stage generate the geometry on the spot. Direct3D 11 (2009) added three stages: the hull shader sets per-patch factors, a fixed-function tessellator spawns the points, and the domain shader places them. OpenGL 4.0 followed in 2010. ATI had tried the concept earlier with TruForm (2001), but without programmability it never caught on.
The payoff is clearest alongside displacement mapping: a smooth surface can carry real bumpy detail without storing a heavy mesh on disk. The factor is dialled down at a distance, making the technique a natural LOD tool. The catch is that excessive tessellation easily tanks fill rate for no visible gain — there are notorious cases of invisible water being tessellated into oblivion.