Subdivision

    Subdivision surface modeling is a method which allows you to create a rough, angular shape made up of a low number of polygons and use a smoothing algorithm to create a smooth shape based on the rough shape.  You can then edit the rough angular shape and watch the resulting changes on the smoothed inner shape in real time.

    Silo's subdivision surfaces are implemented in a manner intended to speed and simplify the process of subdivision surface modeling. There are two ways to create a subdivision surface: using the Subdivide command, and using the Partial Subdivide command. When you first subdivide an object, your original mesh will be retained, while a new, smoothed mesh is created underneath it. This smooth mesh is not directly editable. Instead, it is modified by making changes to the original lower-resolution mesh upon which it is based. You can alter the display of this outer mesh so that it appears that you're editing the inner mesh directly (see Display Options).  Otherwise the outer control mesh will be displayed as a wireframe cage around the subdivided mesh. You can still use all of Silo's polygonal modelling tools to edit the control mesh. If you subdivide the same object multiple times, the same outer control mesh will be used, while the inner subdivided mesh will have increased resolution and get smoother and smoother. You can decrease the resolution, to the point of removing all subdivisions, using the Unsubdivide command. Thus it is easy to switch between different resolutions of subdivision while you're working. If you desire to edit a subdivided shape directly, you can use the Refine Control Mesh command, which will delete the original control mesh and turn the subdivided shape into a regular polygon object.

    The Partial Subdivide command allows you to only subdivide a portion of your object, defined by a selection of either faces or edges. Once you have partially subdivided an object, all Subdivide commands called when that object is selected will further refine the same area, regardless of which areas of the object are currently selected. Calling Partial Subdivide while non-subdivided faces/edges of an object are selected will cause those faces/edges to become subdivided as well.  You can also perform a Partial Subdivide on one portion of the mesh, edit it to your liking, and then use Refine Control Mesh to create a new object, which can have a different partial subdivision. You can also Unsubdivide the mesh to the point where there is no underlying subdivision, at which point you can define a new area to partially subdivide.