12-06-2012, 02:27 PM
Computer Graphics for 3D modeling
3D modeling.pdf (Size: 384 KB / Downloads: 139)
Introduction
An scene can contain different type
of objects (clouds, trees, stones,
buildings, furniture etc.). For all of
them, a wide variety of
representation models are available
• Polygonal surfaces and quadrics
• Spline surfaces
• Volumetric models
• Solid modeling (boundary B-Rep,
spatial division Octrees )
• Procedural models (fractals, particle
systems,…)
• Physic based modeling
Planar surface modeling
• Wireframe modeling
– Elements: points, lines, arcs and circles, conic and curves
– Advantages: easy to build, low memory requirements and storage
– Disadvantages:
• ambiguous representation (hidden-lines removal algorithms)
• lack of visual coherence (line-inclusion algorithms)
• Polygonal modeling
– Polygon mesh: vertex, edges and polygon collection
where each edge is shared by two polygons as
maximum
• vertex: point with coordinates (x,y,z)
• edge: line segment that joins two vertices
• polygon: close sequence of edges
– There are different type of representation that can be
used at the same time in a same application
• Explicit
• Pointers to list of vertices
• Pointers to list of edges
– Criteria to evaluate different representations:
• time
• space
• topological information