Curve modeling – Surfaces are defined by curves, which are influenced by weighted control points.However, polygons are planar and can only approximate curved surfaces using many polygons. The vast majority of 3D models today are built as textured polygonal models, because they are flexible, because computers can render them so quickly.
Polygonal modeling – Points in 3D space, called vertices, are connected by line segments to form a polygon mesh. There are three popular ways to represent a model: Polygon representations are not used in all rendering techniques, and in these cases the tessellation step is not included in the transition from abstract representation to rendered scene. squares) are popular as they have proven to be easy to rasterize (the surface described by each triangle is planar, so the projection is always convex). This step is used in polygon-based rendering, where objects are broken down from abstract representations (" primitives") such as spheres, cones etc., to so-called meshes, which are nets of interconnected triangles. The process of transforming representations of objects, such as the middle point coordinate of a sphere and a point on its circumference into a polygon representation of a sphere, is called tessellation. Level sets are a useful representation for deforming surfaces which undergo many topological changes such as fluids. Polygonal meshes (and to a lesser extent subdivision surfaces) are by far the most common representation. In a shell model of a cube, the bottom and top surface of the cube must have a uniform thickness with no holes or cracks in the first and last layer printed. Shell models must be manifold (having no holes or cracks in the shell) to be meaningful as a real object. Differences between them are mostly variations in the way they are created and edited and conventions of use in various fields and differences in types of approximations between the model and reality. Solid and shell modeling can create functionally identical objects. Almost all visual models used in games and film are shell models. the boundary of the object, not its volume (like an infinitesimally thin eggshell). Shell or boundary – These models represent the surface, i.e. 
Solid models are mostly used for engineering and medical simulations, and are usually built with constructive solid geometry
Solid – These models define the volume of the object they represent (like a rock). The Utah teapot is one of the most common models used in 3D graphics education.Īlmost all 3D models can be divided into two categories: A modern render of the iconic Utah teapot model developed by Martin Newell (1975).
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