4. Basic structure of a CAD system
Application
software
Graphics
utility
Devices
drivers
Input-output
devices
User
interface
Database
(CAD
model)
5. Solid Modeling
Solid models give designers a complete
descriptions of constructs, shape, surface,
volume, and density.
6. Solid Modeling
In CAD systems there are a number of
representation schemes for solid modeling
include:
1. Primitive creation functions
2. Constructive Solid Geometry (CSG)
3. Sweeping
4. Boundary Representation (BREP)
7. Solid Modeling
1. Primitive creation functions
These functions retrieve a solid of a simple
shape from among the primitive solids
stored in the program in advance and create
a solid of the same shape but of the size
specified by the user.
8. Solid Modeling
1. Primitive creation functions
Example:
P: Point
D: Length
W: Width
H: Height
P: Point
R: Radius
H: Height
OR/ first corner and opposite corner OR/ point & Dia & Height
11. Solid Modeling
2. Constructive Solid Geometry (CSG)
There are three basic Boolean operations:
Union (Unite, join)
The operation combines two volumes included
in the different solids into a single solid.
Subtract (cut)
The operation subtracts the volume of one
solid from the other solid object.
Intersection
The operation keeps only the volume common
to both solids.
12. Solid Modeling
2. Constructive Solid Geometry (CSG)
CSG uses primitive shapes as building blocks
and Boolean set operators ( union, -
difference, and intersection) to construct an
object.
Boolean operation on
A & B
A B
13. Solid Modeling
2. Constructive Solid Geometry (CSG)
Boolean operation :
A B
Union (Unite, join)
• The sum of all points in each of two defined sets
(logical “OR”)
• Also referred to as Add, Combine, Join, Merge
Note
(Addition is commutative)
14. Solid Modeling
2. Constructive Solid Geometry (CSG)
Boolean operation :
A - B
Subtract (cut)
• The points in a source set minus the points
common to a second set. (logical “NOT”)
• Set must share common volume
• Also referred to as subtraction, remove, cut
Note
(Subtract is not commutative)
15. Solid Modeling
2. Constructive Solid Geometry (CSG)
Boolean operation :
B - A
Subtract (cut)
• The points in a source set minus the points
common to a second set. (logical “NOT”)
• Set must share common volume
• Also referred to as subtraction, remove, cut
Note
(Subtract is not commutative)
16. Solid Modeling
2. Constructive Solid Geometry (CSG)
Boolean operation :
B A
intersection
• Those points common to each of two defined sets
(logical “AND”)
• Set must share common volume
• Also referred to as common, conjoin
Note
(intersection is commutative)
19. Solid Modeling
2. Constructive Solid Geometry (CSG)
Example
Define the required primitives and Boolean
operations to fully define the given 3D part
21. Solid Modeling
(0, 0, 0)
Primitive Type Primitive configuration
A Cylinder Center (50,150,0) D100 H100
B Box First (0,0,0) Second (100,150,50)
C Box First (30,0,0) Second (70,80,50)
D Cylinder Center (50,150,0) D50 H100
A
B
C
D
22. Solid Modeling
(0, 0, 0)
Primitive Type Primitive configuration
A Cylinder Center (50,150,0) D100 H100
B Box First(0,0,0) First(100,150,50)
C Box First(30,0,0) First(70,80,50)
D Cylinder Center (50,150,0) D50 H100
A
B
C
D
(A B)
A
(A B) - C
((A B) – C) - D
25. Solid Modeling
(AB) - C
Primitive Type Privative configuration
A Cylinder Center (50,100,0) D100 H200
B Box First(0,0,0) second(100,200,50)
C Cylinder Center (50,100,0) D50 H200
A
B
C
26. Solid Modeling
In CAD systems there are a number of
representation schemes for solid modeling
include:
1. Primitive creation functions
2. Constructive Solid Geometry (CSG)
3. Sweeping
4. Boundary Representation (BREP)
