trueSpace Sweeps1 Sep, 2003 By: John E. Wilson
This month we will explore the trueSpace tools for creating 3D polyhedra objects from 2D curves. Unlike NURBS 3D objects (which we will examine in a future column), the surfaces of polyhedra 3D objects are faceted. As a result, rounded surfaces are not perfectly smooth. You can, though, create relatively smooth rounded surfaces by increasing their relative number of facets. To do this, right click a tool's button to display its Property panel, and increase the value in the Segments edit box. Also, polyhedra 3D objects assume a smooth appearance when they are rendered.
trueSpace uses the DrawPanel, shown in Figure 1, as an interface for drawing 2D curves. You can insert the DrawPanel by selecting its tool button (its location is shown in Figure 1), and then clicking somewhere on the trueSpace xy plane. You can also click and drag to establish the initial location, orientation, and size of the DrawPanel. Once you have inserted it, a toolbar for creating 2D curves is displayed nearby. An alternate method of inserting the DrawPanel is to select a 2D curve tool from the Object Tools toolbar, and draw a curve. The DrawPanel automatically appears when you complete the curve.
You can change the size of the DrawPanel by dragging one of its three gray-colored sides or by dragging the rectangle in its lower-right hand corner. You can move the DrawPanel, along with any curves you have drawn, by dragging its blue edge, or by dragging the round gray area of the panel's NAV controller (you can see this in Figure 1). The NAV controller has three axes that you can use to rotate the DrawPanel. Click the rectangle in the upper-left corner of the panel to toggle between a perspective view and an orthogonal viewpoint.
Figure 1. trueSpace uses the DrawPanel as an interface in drawing 2D curves that are suitable for creating 3D objects. Once you have drawn a curve, you can edit it through the context-sensitive Curve Edit toolbar.
2D Curve Drawing Tools
trueSpace has 15 tools, which are available from the Object toolbar or from the context-sensitive toolbar that is displayed when you insert the DrawPanel, for you to use in creating 2D curves. Most of these tools are for drawing curves having regular geometric shapes, such as circles, arcs, and ellipses. The Add Regular Polygon tool is for drawing triangles, rectangles, hexagons, and so forth. To establish the number of sides of the polygon, first right click the tool to display its Property panel and enter a value in the edit box.
Often you will use the Add Curve tool to draw a complex profile for creating a 3D object. In using it, click anywhere on the DrawPanel to start the curve, and then click to establish each of its subsequent points. The curve passes through each point you pick. The Curve Edit toolbar displays as you draw the curve, and you can use its Close Curve tool to end the curve by creating a segment from your last point to your first. To leave the curve open, hit the space bar. The Add Polyline tool works similarly, but the curve segments are straight.
Editing 2D Curves
Once you have created a 2D curve, you can edit it by right clicking it to display its control points along with the Curve Edit toolbar, as shown in Figure 1. In this toolbar, Closed Curve closes an open curve, and Open Curve opens a closed one. Use the Draw New Curve Point tool to add segments to an existing open curve. You can add points within a curve with the Insert New Curve Point tool, and you can remove a selected point with the Delete Curve Point tool. The Sharp Corner tool creates sharp corners in a curve, as shown in Figure 1, and the Smooth Corner tool transforms sharp corners into smooth ones. When you use these two tools, the change is throughout the curve if the Change Curve Parameter for All Points tool is active; however, only the currently selected point is affected if the Change Curve Parameter for Selected Point Only tool is active.
The Move Curve Point tool allows you to move the currently selected point. Hold down the left mouse button to drag the point in the plane of the DrawPanel, or hold down the right button to drag the point perpendicularly to the DrawPanel. Right click the tool to display the Coordinates panel (shown in Figure 1), which provides additional controls in moving curve points.
The control points of the curve you are editing appear as small yellow squares; and, when you select a point, a line extending from both sides of the point and tangent to the curve appears. trueSpace refers to it as the Control Point Handle. The control point handles of the end points of open curves, though, extend only in one direction. Click the end of a control point handle and rotate the handle to change the tangency of the curve at the point, and stretch the handle to change the relative power, or weight, of the control point.
Polyhedron Sweep Tools
trueSpace refers to the tools--Sweep, Macro Sweep, Lathe, Bevel, and Tip--that create 3D polyhedra objects from curves as the Sweep tools. The curve must be closed. You can access them from Object Tools. They can also be used with the selected face of an existing polyhedron object, and, consequently, they are in the context sensitive toolbar that displays as you edit a polyhedron object.
The Sweep tool linearly extrudes curves by the z value in the tool's Property Panel. If, however, it is used on the selected face of an existing polyhedron that is angled from its opposite face, it doubles that angle as the face is extruded. Thus, if the selected face of a cube is slanted 22.5 degrees, the end face of the resulting sweep will be slanted 45 degrees; and, if you sweep that face, the resulting end face will be slanted 67.5 degrees.
The Macro Sweep tool sweeps the selected curve or face along one of the predefined paths in the trueSpace Path Library.
The Lathe tool revolves the selected curve or face about an axis. It can also create helix-shaped polyhedra. When you initiate this tool, trueSpace displays an axis encircled by a rotational arc, or circle, that you can move and modify, and displays the same context-sensitive toolbar you get when editing a polyhedron object. When you've set your parameters, reselect the Lathe tool to create the 3D polyhedron. Figure 2 shows the Lathe's axis and its rotational arc, along with the resulting polyhedron rendered in an inset.
Figure 2. Use the trueSpace Lathe tool to create a 3D polyhedron object by revolving a closed 2D curve about an axis. When you select this tool, trueSpace displays an axis encircled by an arc representing the angle of revolution. A rendered view of the 3D object created by revolving this curve is shown as an insert.
The Bevel tool extrudes the selected curve or face linearly as it tapers its sides. Set both the extrusion distance and the taper angle in the tool's Property panel.) The Tip tool extrudes them to a point.
Operating system: Windows 95, 98, ME, XP, NT 4, 2000, or XP Pro. The program's facial animation tools, though, do not work in Windows 95.
Minimum hardware: Pentium, or equivalent, microprocessor, 64MB RAM, 50MB hard disk space, 16MB video, CD-ROM drive.
Autodesk Technical Evangelist Lynn Allen guides you through a different AutoCAD feature in every edition of her popular "Circles and Lines" tutorial series. For even more AutoCAD how-to, check out Lynn's quick tips in the Cadalyst Video Gallery. Subscribe to Cadalyst's free Tips & Tools Weekly e-newsletter and we'll notify you every time a new video tip is published. All exclusively from Cadalyst!