Tessellation (computer graphics)

In computer graphics, tessellation is the process of dividing the polygon datasets that describe objects in a scene into structures suitable for rendering, most often triangles for real-time work, as in OpenGL 4.0 and Direct3D 11. Its main advantage for real-time graphics is that detail can be added to or removed from a 3D polygon mesh and its silhouette edges on the fly according to control parameters such as camera distance, which earlier pixel-level techniques such as parallax mapping and bump mapping could not do for silhouettes. In the Direct3D 11 pipeline the primitive is the patch, and the tessellator produces a triangle tessellation of each patch controlled by parameters such as the TessFactor; in OpenGL 4.0 a Tessellation Control Shader and four tessellation parameters play the same role. Offloading the work to GPU hardware lets smoothing happen in real time, and tessellation also supports subdivision surfaces, level of detail scaling and fine displacement mapping. In computer-aided design the same word names the approximation of a boundary-representation solid by a mesh of small tetrahedra or hexahedra for finite element analysis, controlled by limits on sag, polygon size and the angle between adjacent polygons.