Use the SPHERE command to construct by defining the center of the SPHERE along with a radius or diameter. As with the Cylinder, the central axis of a SPHERE is along the Z axis of the current user coordinate system. In figure 9-25 the SPHERE is constructed in wire frame mode
and does not look like much of a SPHERE. Perform a hidden line removal using the HIDE command to get a batter view of the SPHERE.
Command: SPHERE Center of the sphere<0,0,0>:
Diameter/<radius> of sphere Diameter: 4
Command: HIDE
The TORUS Command
A TORUS is formed when a circle is revolved about a line in the same plane as the circle. In the other words a TORUS is similar to a 3D doughnut. The TORUS may be constructed using either a radius or diameter, method. When using the radius method. Two radius values must be used to define the TORUS; one for the radius of the tube and the other for the radius from the center of the TORUS to the center of the tube. Use two diameter values when specifying a TORUS by diameter. Once you construct the TORUS, it lies parallel to the current user coordinate system similar to Figure 9-26.
Command: TORUS
Center of the torus<0,0,0> (identify the center of the tours through coordinate entry or by picking)
Diameter/<Radius> of torus: 5 (Foe the Radius of the torus at “A”) Diameter/<Radius >of the tube: 1(For the radius of the tube at “B”) Diameter: 4
Diameter <radius>of tube: D (for the diameter of the tube at the “D”) Diameter 2
Using Boolean operations
To combine of one or more primitives to form a common solid a system is available to illustrate the relationship between the individuals that make up the solid model. This system is called a Boolean operation. Boolean operation must act on at least a pair of primitive regions or solids.
Boolean operations allow you to add two or more objects together subtract a single or group of objects from another or find the over lapping volume in other word to form the solid common to both primitive, highlighted in figure 9-27 or the Union Subtract and Intersect command that you use to perform the Boolean operation previously explained. Figure 9-28.
The Union Command
This construction operation join to or more selected solid object together in to a single solid object. See figure 9-33
The SUBTRACT Command
Use this command to subtract one or more solid object from a source object. See figure 9-32 The INTERSECT Command
Use this command to find the solid command to a group of selected object solid. Figure.
Command: INTERSECT
Select object (pick the box and cylinder)
Select object (press enter to performed the intersection operation)
3D Application of Union Solid
Figure 9-34 shows an objects consisting of one horizontal solid box to vertical solid boxes and to extruded semi circular shape. All primitive have been positioned with the MOVE command to join all solid primitives in to one solid object use the union command. The order of selection of these solids for this command is not important. Use the following prompt and figure 9-34.
3D Application of Moving solid
Using the same problem from the previous example let us now add a hole in center of the base.
The cylinder was already created using the CYLINDER command. It now needs to be move to the exact center of the base. You may use the move command along with the Osnap tracking mode to accomplish this Tracking mode will automatically activate the ortho mode when it is in use.
Command: Move
Select object: (select the cylinder at; A ;)
Select object :( Press enter to continue with this command) Base point or displacement: Mid
Of (select the bottom of the cylinder at; A ;)
Second point of displacement: TK (to activate tracking mode) First tracking point: Mid
Of (select the midpoint of the bottom of the base at ;) Next point (press enter to end tracking): Mid
Of (select the midpoint of the bottom of the base at; C ;) 3D Applications of Subtracting solid
Now that the solid cylinder is in position use the SUBTRACT command to remove the Cylinder form the base of the main solid and create a hole in the base. See figure 9-35
Command: SUBTRACT
The select solid regions to subtract form select object: (select the main solid and source at “A”) Select object (press enter to continue with this command)
Select object region to subtract select objectselect the cylinder at “B”) 3D Application of Aligning Solids
Two more holes need to be added the vertical side of the solid object. A cylinder was already constructed however it is in the verticals position. This object needs to be rotated and moved into a position. The align command would be a good command to use in this situation. The series of source and destination points guide placement of one object of another. The object rotates and moves into position use the following command prompt sequence and figure 9-36 for the align command. The cylinder is removed to create holes in each of the vertical sides of the solid object using the subtract command the completed object shown in figure 9-37.
Command: Align
Select object (select the cylinder)
Specify 1st source point: Cen (select the bottom of the cylinder at; A ;) Specify 2nd source point: Cen (select the bottom of the cylinder at; B ;) Specify 2nd source point: Cen (select the bottom of the cylinder at; C ;) Specify 2nd destination point: Cen
Creating Solid Extrusions
The EXTRUDE command create a solid by Extrusions. Only polyline and circle may be EXTRUDED.
Once object are polyline us the following prompt to construct solid EXTRUSION for the object in figure 9-38.
For the height the extrusions a positive numerical value may be entered are the distance may be determined by picking two points on the display screen.