It's Magic

You can create trueSpace 3D objects directly in basic geometric shapes, which are referred to as primitives, rather than by revolving or extruding wire profile objects. You can then work with the faces, edges, and points of those primitives to achieve the shape you are after. Consequently, trueSpace has numerous tools for creating and working with primitives, and we will explore them this month.

Primitive Types
The buttons, or icons, as trueSpace calls them, for creating primitives are on the left end of the Object toolbar, which by default is located on the lower left edge of the trueSpace window. The tools can also be accessed from the Primitives library panel located on the left edge of the trueSpace window. Once opened, you can, as shown in Figure 1, drag the Primitives library panel to any location. The primitives come in three different object types.

• Polyhedras are the basic trueSpace 3D objects. They are comparable to solids in some modeling programs in that you can modify them with Boolean operations. Their surfaces consist of multi-sided polygons that you can use for editing the 3D object.
• NURBS are 3D objects that have surfaces based on Non-Uniform Rational B-Spline algorithms. They are comparable to surface objects in some modeling programs.
• Metaballs are unique trueSpace objects with dynamic surfaces that interact and melt together to create complex organic 3D shapes.

The tool icons for polyhedra primitives are colored brown, the ones for NURBS are blue, and those for metaballs are green. This column concentrates on polyhedra primitives.

Figure 1. As you create trueSpace polyhedra primitives, you can change their size and shape through the Magic Ring shown here on the right. The three 3D objects shown in this figure were all easily created by using the Magic Ring to modify basic cube primitives. The Primitive Shape and Primitive Parameters panels numerically display the results of the Magic Ring modifications, and, alternately, you can enter new values in the panels to change the primitive.

Creating Primitives
Three settings in the File >Preferences dialog box determine where and how primitives are created. When On Grid is selected, the lower surface of the primitive is positioned on the xy plane; otherwise its centroid is positioned on the xy plane. When Automatic, of the Automatic/Scalable toggle, is active, a primitive is created at the intersection of the x and y axes as soon as you invoke a tool for creating a primitive. When Scalable is active, you must pick an insertion point for the primitive. The third setting, Magic Ring, which affects only polyhedra primitives, is described in the next section.

You can establish some of the basic properties of a primitive before it is created by right-clicking its icon, which will cause it to display a property panel. The property panel for a polyhedron cube, which is shown in Figure 1, contains only one property: Resolution, which is the number of divisions on each face of the cube. When resolution is set to its default value of 1, each face of a cube is undivided. When it is set to 4, each face is divided by four vertical and four horizontal grid lines.

After left-clicking the icon of a primitive (provided the Scalable toggle is active), a small box icon appears next to the screen cursor, and if you click the left mouse button, the primitive is created and centered on the point that you picked. If you hold down the left mouse button, though, you can drag the mouse to set the base size of the primitive and then depress the right mouse button (without releasing the left one) and drag the mouse to set the primitive's height.

The Magic Ring
As soon as you create a polyhedron primitive, the Magic Ring appears within the object, provided Magic Ring has been selected in the Files >Preferences dialog box. It has four regions (also shown in Figure 1) that you can hook on to and use via your mouse to change the size and shape of the primitive. Although each turns yellow when you move the screen cursor over it, each region has one of these distinctive colors:

• red, with the region appearing as a thick red line extending from the edge of the primitive's top surface to its center, down its centerline to the bottom surface and then along the bottom surface back to the vertical edge (even though this red line has three segments, it makes no difference which segment you work with);
• green, with the region appearing as a thick green line extending along the vertical surface of the primitive;
• blue, with the region appearing as a blue diamond that lies near the middle of the green line;
• brownish yellow, with the region appearing as a brownish yellow arc that lies in two places between the red and green regions. It's arc shape, however, is initially hard to see on cube, cylinder, and cone primitives. (Note: this region has two separate segments, and it makes no difference which segment you use.)

When using the Magic Ring, you move the screen cursor to a region by depressing either the left or right mouse button, and moving the mouse to create your desired modification. For example, move the cursor to the red region, depress the left mouse button, and move sideways to change the x and y dimensions of the primitive. Or, move vertically to pull the surface center point of the primitive up or down. (Thus, the top and bottom surfaces of a cube become pyramids.) Conversely, hold down the right button to change the number of polygon divisions of the top and bottom surfaces of the primitive.

When you right-click the button for the primitive tool you are currently using, trueSpace displays two panels, each having seven fields that numerically represent the results of a Magic Ring action. One panel is labeled Primitive Shape and the other Primitive Parameters. As you work with the Magic Ring, the values in the applicable fields change, and, alternately, you can change the shape and size of the primitive by entering new values into these fields.

When using the Magic Ring, the tool for the primitive you are creating remains active. If you pick a point off the Magic Ring, work ends on the current object and a new primitive that is a clone of the previous one is created, complete with its own Magic Ring.

Figure 2. trueSpace's Point Edit mode has the tools shown here for modifying the faces of polyhedra primitives. With these tools you can transform a cube primitive into a ball, manipulate its faces, and then smooth them to create the head of a mythical creature.

Polyhedra Primitives
Once you have finished your initial work with a primitive, you can't restore its Magic Ring. You can, though, edit primitive polyhedras by activating the object tool, selecting a primitive to display the selector cage that was discussed in last month's column (CADENCE, July 2003, "Introducing trueSpace"), and right clicking anywhere on the primitive to dismiss the selector cage and display the polyhedron edit toolbar shown in Figure 2. Caligari refers to this as the Point Edit mode. Through these tools you can operate on, modify, and add to the polygons that make up the polyhedron's surface. Thus, as shown in Figure 2, you can start with a cube primitive, transform it into a round object, manipulate its faces, and lastly smooth it to create a mythical creature. Creating 3D objects in trueSpace is somewhat analogous to creating objects in clay.