Polyface Mesh and 3D Polylines
3D Polylines
A Polyline is an AutoCAD graphic entity which is best explained as a set of one or more "special" line segments. The segments are "special" for two reasons.
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They are not recognised, by AutoCAD, as simple "line segment" entities.
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They have more functionality than simple "line segment" entities. e.g. they can have a visible THICKNESS.
A single polyline entity can be composed of multiple segments. i.e. when you edit [e.g. erase] a polyline, you edit all of its segments with one operation.
e.g. You can create a rectangle with a single polyline, composed of 4 segments.
A 3D polyline is a "special" AutoCAD polyline used for creating 3D objects.
Polygon mesh
A polygon mesh is a single entity wireframe representation of a 3D object e.g. a sphere.
It is constructed with the "special" segments used in 3D polyline construction.
Polyface mesh
A polyface mesh is a single entity wireframe representation of a 3D object e.g. a sphere.
It is constructed with the "special" segments used in 3D polyline construction.
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It has the added property of having FACES. i.e. when a HIDE, SHADE or RENDER is done faces are regarded as OPAQUE [NOT TRANSPARENT].