Modifier - Subdivision
SubPatch Display and Render Levels
SubPatch objects may be used in Layout as any other object. In Layout, the Object Properties Panel includes two settings that are important when you use SubPatch objects. The Display SubPatch Level and Render SubPatch Level settings determine the level of subdivision smoothing needed for display and rendering purposes, respectively. These values, generally, have an effect similar to Modeler’s Patch Divisions (General Options Panel) setting, discussed next.
The SubPatch levels may be set to zero. This is similar to a level of one, except that the patches are not continually remeshed, even if Subdivision Order is not set to First. In other words, a level of zero makes patches act like normal polygons, and this allows faster interaction.
Adaptive Pixel Subdivision (APS) is a system of subdividing an object. With APS an object can be subdivided per polygon, by a texture, or even by pixels. It works by computing the subpatch level for each polygon, and storing those levels in a VMap.
Additional Settings for Render Subpatch Level
Per Object - The classic method of having the same subdivision level for the entire mesh.
Per Polygon - Sets the Subdivision level per Cage Mesh polygon independently (commonly referred to as variable subdivision)
Pixels Per Polygon - Ties the amount of pixels of the output frame to the subdivision level of the cage polygons. For example, a setting of 4 means that a given polygon will have an area no larger than 4 pixels.
Metaball Display and Render Levels
These are the resolutions for OpenGL and rendertime for Metaball objects.