Unit 66 - 3D Modelling: 3D - The Basics: Mesh Construction

Mesh Construction

A polygon mesh is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling. The faces usually consist of triangles, quadrilaterals or other simple convex polygons, since this simplifies rendering, but may also be composed of more general concave polygons, or polygons with holes.

Box Modeling

This is a technique that is used in 3D modelling where the model is created by modifying primitive shapes to create a rough draft of the final model, in most cases. A primary function of box modeling involves extruding and scaling the faces, which are the flat planes that make up a model.

Extrusion Modelling

Extrusion is a method of adding geometry to a polygon primitive, and one of the primary tools a modeler uses to begin shaping a mesh.

Through extrusion a modeler manipulates the 3D mesh by either collapsing a face in upon itself (to create an indentation), or by extruding the face outward along its surface normal—the directional vector perpendicular to the polygonal face.

Extruding a quadrilateral face creates four new polygons to bridge the gap between its starting and ending position.

Primitive Modeling

This is the simplest way of modeling three dimensional objects. Using geometric primitives such as cylinders, cones, cubes and balls, complex models are created. This approach ensures easy construction as the forms are mathematically defined and precise. Primitive modeling is mainly used in developing 3D models of technical applications.

Specialist modeling

During last decades different research lines has been explored to improve the humancomputer interface in CAD systems. Sketch-based interfaces and modelling (SBIM) is an

emerging research field, and seems to be able to create the computer tools required to shift

(Igarashi and Zeleznik, 2007) to a new paradigm where sketches should be used as input to

create digital engineering models in a true computer-aided ideation environment. Recent

advances in the field of SBIM promise better integration of those separated worlds (sketching

and CAD tools).