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How are subdivision surfaces used in visual effects?
Subdivision surfaces are a common modeling primitive that has gained popularity in animation and visual effects over the past decades. As the name suggests, subdivision surfaces are fundamentally surfaces.
How does a subdivision surface get its name?
Subdivision surfaces get their name from this dividing into regions of greater detail. You start with a base mesh and divide and subdivide regions into finer and finer detail, with each subdivision giving greater control in that area. You reshape subdivision surfaces by modifying control points at the different levels of the hierarchy.
How are subdivision surfaces similar to parametric surfaces?
Just as rectangular piecewise parametric surfaces have a collection of control points (its cage stored as a grid) and an underlying surface, subdivision surfaces also have a collection of control points (its cage stored as a mesh) and an underlying surface (often referred as its “limit surface”).
Which is better a subdivision surface or a piecewise surface?
A single polygonal mesh can represent shapes with far more complexity than a single rectangular piecewise surface, but its faceted nature eventually becomes a problem. Subdivision surfaces combine the topological flexibility of polygonal meshes with the underlying smoothness of piecewise parametric surfaces.
Why do subdivision surfaces always have extraordinary points?
Loop subdivision surfaces have extraordinary points for each vertex in the original mesh that had a valence other than six. It is impossible to form a closed surface entirely out of vertices of valency six, so Loop surfaces will always have extraordinary points.
Which is an irregular feature of a subdivision?
Irregular features come in a number of forms. The most widely referred to is an extra-ordinary vertex, i.e. a vertex which, in the case of a quad subdivision scheme like Catmull-Clark, does not have four incident faces.
How are subdivision surfaces derived from base mesh?
Subdivision surfaces are polygon mesh surfaces generated from a base mesh through an iterative process that smooths the mesh while increasing its density. Complex smooth surfaces can be derived in a reasonably predictable way from relatively simple meshes.