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Modifying VectorWorks 3D Object

1 Apr, 2003 By: John E. Wilson


This is the third in my series about the 3D features of VectorWorks, an $895 2D drafting and 3D modeling program from Nemetschek North America that runs on computers using either Mac or Windows operating systems (www.nemetschek.net).

My previous column ("Creating 3D Objects in VectorWorks") focused on the VectorWorks tools, which are initiated from buttons on tool palettes, and its commands, which are invoked from screen pull-down menus, that create basic 3D objects. This one column will describe how to combine and modify those 3D objects to create complex 3D models.

Boolean Operations
As does virtually every 3D modeling program, VectorWorks supports the three Boolean operations--Add, Subtract, and Intersect. The Add operation combines the volume of two or more 3D objects. Subtract removes the volume that one or more 3D objects share with a specified 3D object, and Intersect leaves only the volume that is shared between two or more 3D objects.

Usage of the Add and Subtract operations is straightforward because the Add operation is somewhat similar to fusing components together and Subtract is similar to drilling holes or milling away portions of a base part. Usage of of Intersect is not so obvious, but it is a very handy operation. It can, for example, transform 2D drawings into 3D objects, as shown in Figure 1. The outline of the part in each of the three drawing views shown in panel A of the figure are extruded to create the three 3D objects shown in panel B. These objects are then moved together, as shown in panel C, and the Intersect operation creates the 3D model shown in panel D.


Figure 1. You can use the Boolean intersect operation to create a 3D model from a multiview 2D drawing.

The names of the VectorWorks commands for the Boolean operations are Add Solids, Subtract Solids, and and Intersect Solids, and they are accessed from the Model tab of the screen pull-down menu. Although--despite their names--the operations do work with surface objects, you will generally use them on 3D objects that are completely enclosed by a unified surface. You must preselect at least two objects before you invoke the commands. The Add and Intersect operations are performed without any further action from you, but the Subtract operation displays a dialog box for you to use when specifying the object whose volume the others will subtract from.

Editing 3D Objects
When you select a VectorWorks' 3D object, its dimensions will display in the Object Info palette. You can modify many of them. For example, you can change the height and the angle of a tapered extrusion. You'll find that when constructing helix-shaped objects (with the Sweep command) this is an especially convenient way to see the results of the radius, pitch, and angle values as you set them. To change the size and shape of profile objects, select the 3D object and then invoke the Organize >Edit Group command to display the editable dimension values of the profile object in the Object Info palette. Invoke the Organize >Exit Group command to restore the edited 3D object.

The 3D Reshape tool, which is in the 3D Tool palette, allows you to use your pointing device to change the size of sphere, hemisphere, and cone primitives; the path shape of Extrude Along Path objects; and the height of extruded objects. As you use this tool, nodes appear on the object you select, and when you move the screen cursor over a node the cursor will change its appearance to indicate the directions you can move the node in. This tool is especially useful in changing the shape of NURBS surface objects, which I will address next month.

Editing 3D Objects
VectorWorks does not have any editing operations specifically for modifying the results of Boolean operations. You can, though, use the Organize >Edit Group command to temporarily return the 3D object to its condition prior to the last Boolean operation. Thus, for example, if you have made a round hole in an object by subtracting a cylinder from it, and then decide the hole should have a different diameter or be in a different location, the Organize >Edit Group command will restore the cylinder to enable you to move it or change its extrusion height, and to change its diameter by invoking Organize >Edit Group again to display the editable parameters of the cylinder's circular profile object. When you have finished, invoke the Organize >Exit Group command twice to restore the solid.

Fillets and Chamfers
The Blend Edge tool of VectorWorks' 3D Power Pack palette rounds the sharp edges of 3D objects and, as an option, can also bevel sharp edges. You specify the parameters and the options of the tool through a dialog box, and then you select the edges you want to blend. When two edges are close together, as those highlighted in red in the upper left-hand corner of Figure 2, the blend will fail. In the particular case shown in Figure 2, though, you can fillet the edges by postponing the addition of the cylinder and the box-shaped object until you have filleted the edges of the box, as shown in the upper-right. Next, you would unite the two 3D objects with the Add Solids command and then select the edges around the cylinder, as shown in the lower-left, to achieve the results shown in the lower-right of Figure 2.


Figure 2. VectorWorks' Blend Edge tool rounds or chamfers the sharp edges of 3D objects, but the tool will not work when two edges are close together, as shown in the upper left of this figure. By postponing the Add operation, however, you can round those edges.

Once a set of edges has been filleted or chamfered, you can edit the fillet radius or the chamfer setback from the Object Info palette. You cannot, though, edit them on an edge-by-edge basis. Therefore, if you have created a 2mm fillet on three edges during one use of the Blend Edge tool, you can change the radius on all three edges, but you can't change the radius on just some of them. You must use the Organize/Ungroup command to remove the fillets and then remake them.

Slicing Operations
The VectorWorks Model >Cut 3D Section command slices through a 3D object and creates a new 3D object on a specified side of the slicing plane. The Model >Cut 2D Section command, on the other hand, creates a new 2D object from the portions of a 3D object that intersect a slicing plane. Neither command affects the original 3D object, while the new 2D or 3D object is automatically placed in a new layer. Both commands prompt you to define the slicing plane by drawing a line. The slicing plane is perpendicular to that line. The Model >Cut 3D Section command then prompts you to specify which side of the plane is to be the basis of the new 3D object, and the Model >Cut 2D Section command prompts you to specify a viewing direction for the new 2D object.

The Model >Section Solids command uses a surface object to slice a 3D object. Unlike the 2D and 3D Section commands, one portion of the sliced 3D object is discarded. The command requires you to pre-select two objects, one of which should be a surface object. You will be prompted to specify which of the two objects you want to serve as the slicing object, and that object must extend beyond the object you want to section. All of the volume of the 3D object that is on the positive side of the slicing object is removed. You can, though, reverse the section side in the Object Info palette. If you happen to use a 3D object as a slicing object, the result is similar to that of the Subtract Solids command.


About the Author: John E. Wilson


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