Edge loops
Encyclopedia
An edge loop, in computer graphics
, can loosely be defined as a set of connected edges across a surface
. Usually the last edge meets again with the first edge, thus forming a loop. The set or string of edges can for example be the outer edges of a flat surface or the edges surrounding a 'hole' in a surface.
In a stricter sense an edge loop is defined as set of edges where the loop follows the middle edge in every 'four way junction'. The loop will end when it encounters another type of junction (three or five way for example). Take an edge on a mesh surface for example, say at one end of the edge it connects with three other edges, making a four way junction. If you follow the middle 'road' each time you would either end up with a completed loop or the edge loop would end at another type of junction.
Edge loops are especially practical in organic
models which need to be animated. In organic modeling edge loops play a vital role in proper deformation of the mesh. A properly modeled mesh will take into careful consideration the placement and termination of these edge loops. Generally edge loops follow the structure and contour of the muscles that they mimic. For example, in modeling a human face edge loops should follow the orbicularis oculi muscle
around the eyes and the orbicularis oris muscle
around the mouth. The hope is that by mimicking the way the muscles are formed they also aid in the way the muscles are deformed by way of contractions and expansions. An edge loop closely mimics how real muscles work, and if built correctly, will give you control over contour and silhouette in any position.
An important part in developing proper edge loops is by understanding poles. The E(5) Pole and the N(3) Pole are the two most important poles in developing both proper edge loops and a clean topology
on your model. The E(5) Pole is derived from an extruded face. When this face is extruded, four 4-sided polygon
s are formed in addition to the original face. Each lower corner of these four polygons forms a five-way junction. Each one of these five-way junctions is an E-pole. An N(3) Pole is formed when 3 edges meet at one point creating a three-way junction. The N(3) Pole is important in that it redirects the direction of an edge loop.
Computer graphics
Computer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware....
, can loosely be defined as a set of connected edges across a surface
Surface
In mathematics, specifically in topology, a surface is a two-dimensional topological manifold. The most familiar examples are those that arise as the boundaries of solid objects in ordinary three-dimensional Euclidean space R3 — for example, the surface of a ball...
. Usually the last edge meets again with the first edge, thus forming a loop. The set or string of edges can for example be the outer edges of a flat surface or the edges surrounding a 'hole' in a surface.
In a stricter sense an edge loop is defined as set of edges where the loop follows the middle edge in every 'four way junction'. The loop will end when it encounters another type of junction (three or five way for example). Take an edge on a mesh surface for example, say at one end of the edge it connects with three other edges, making a four way junction. If you follow the middle 'road' each time you would either end up with a completed loop or the edge loop would end at another type of junction.
Edge loops are especially practical in organic
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...
models which need to be animated. In organic modeling edge loops play a vital role in proper deformation of the mesh. A properly modeled mesh will take into careful consideration the placement and termination of these edge loops. Generally edge loops follow the structure and contour of the muscles that they mimic. For example, in modeling a human face edge loops should follow the orbicularis oculi muscle
Orbicularis oculi muscle
The orbicularis oculi is a muscle in the face that closes the eyelids. It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament.From...
around the eyes and the orbicularis oris muscle
Orbicularis oris muscle
In human anatomy, the orbicularis oris muscle is the sphincter muscle around the mouth."Orbicularis Oris is a complex of muscles in the lips that encircle the mouth; until recently it was misinterpreted as a sphincter, or circular muscle, but it is actually composed of four independent quadrants...
around the mouth. The hope is that by mimicking the way the muscles are formed they also aid in the way the muscles are deformed by way of contractions and expansions. An edge loop closely mimics how real muscles work, and if built correctly, will give you control over contour and silhouette in any position.
An important part in developing proper edge loops is by understanding poles. The E(5) Pole and the N(3) Pole are the two most important poles in developing both proper edge loops and a clean topology
Topology
Topology is a major area of mathematics concerned with properties that are preserved under continuous deformations of objects, such as deformations that involve stretching, but no tearing or gluing...
on your model. The E(5) Pole is derived from an extruded face. When this face is extruded, four 4-sided polygon
Polygon
In geometry a polygon is a flat shape consisting of straight lines that are joined to form a closed chain orcircuit.A polygon is traditionally a plane figure that is bounded by a closed path, composed of a finite sequence of straight line segments...
s are formed in addition to the original face. Each lower corner of these four polygons forms a five-way junction. Each one of these five-way junctions is an E-pole. An N(3) Pole is formed when 3 edges meet at one point creating a three-way junction. The N(3) Pole is important in that it redirects the direction of an edge loop.