After completing this chapter you will be able to: Understand the terminology used in 3-D modeling, define the most popular types of 3-D modeling systems, apply Boolean operations to 3-D objects, understand the role planning plays in building a constraint-based model.
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Solid Modeling – Primitives and Boolean Operations
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Solid Primitives
Primitives are simple solid objects
created directly in a CAD system Examples include: box, sphere, cylinder, cone, wedge, torus
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Model Building in AutoCAD
Length in x axis direction
Width in y axis direction
Height in z axis direction
Length, width and height can be
positive or negative
A positive dimension indicates
movement in direction of positive axis
A negative dimension indicates
movement in opposite, or negative
direction
In AutoCAD, the following dimensions are associated with the three coordinate axes:
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Solid Composites
Primitives combined using Boolean
operations to create solid composites
Boolean operations used in solid modeling are:
Union
Intersection
Subtraction
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Union
Union means set of all elements
belonging to either A or B
A B
Union of two or more solids
creates a composite solid
composed of combined volumes
of these solids
In set theory, the union of two sets, A and B, is represented pictorially as:
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Intersection
Set of all elements belonging
to both A and B
Intersection of two or more
solids
creates a composite solid
composed of volume common
to original solids
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Subtraction 1
Set of all elements
belonging to A but not B
A – B
Subtraction of two solids
creates a composite solid
composed of volume of
first solid minus common volume shared with second solid
Subtraction of two sets, A and B:
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Subtraction 2
Alternatively, B A is
represented pictorially as:
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Solid Modeling – Primitives and Boolean Operations
Chega!