Working with Bodies [N-World Contents] [Book Contents] [Prev] [Next] [Index]

Working with Bodies (cont.)

: Note. The Reverse command is particularly useful for changing the direction of a trajectory that you want to animate an object along in N-Dynamics.
: Note. Reverse doesn't change the shape of the wire or reorder it's segments; it only reverses the designated "beginning" and "end."

Rotate

Edges, faces, polyhedra, vertices

Rotates the element around global axes passing through a selected center.

(CLICK-L) rotates around the element's normal through the element's midpoint.

Figure 4.108 Left, original cube; right, copy rotated around its own Y-axis

(CLICK-M) rotates the element around the selected axis (the axis menu described is described in detail for the section "Axis Move," on page 4-3).

Figure 4.109 Left, original cube; right, copy with selected face rotated around global-Z axis

(CLICK-R) lets you select an axis about which the element is to be rotated; you are also prompted to select which element the object is to be rotated around. The selectable axes are identical to those described for the operation "Axis Move," on page 4-3 and the selectable elements the same as those described for "Position," on page 4-72.

Rotate Normal

Vertices of a polyhedron

Interactively adjusts the orientation of the normal for a selected vertex. This lets you adjust the apparent position of any light striking an object, since lighting is based on the relationship between a vertex's normal and the angle at which light strikes the area around that vertex.

While you can rotate the normal of an object displayed in wire frame mode, the effect is much more visible if you turn on Shading for the object.

This feature can be used, for example, to tweak the appearance of a pre-lit object being sent to a 3D game system.

To rotate a vertex's normal:

1. Assign a material to the object.

2. (CLICK-L) on points on the element sensitivity menu.

3. (SHIFT-L) on the vertext whose normal you want to move.

You might, for example, want to tone down how directly the light appears to be striking the front of an object.

4. (CLICK-L) on Rotate Normal and move the mouse.

Figure 4.110 Left, original dodecahedron; right, after rotating the normal of the vertex shown

: Note. To revert the normal to its original orientation, (SHIFT-L) on the vertex, then (CLICK-M) on Rotate Normal.

Saturation

Ambient, point, infinite, and spot lights

Interactively adjusts the saturation (purity) of a light's color. For example, pure blue has a high saturation. As saturation decreases, pure blue becomes a pastel blue before turning to a gray.

To adjust the saturation of a light interactively:

1. (CLICK-L) on points on the element sensitivity menu.

2. (SHIFT-L) on the light, then (CLICK-L) on Saturation.

Move the mouse left and right to adjust the saturation of the light.

As you move the mouse, both the body and its emitted light update interactively. Note that as the light becomes less saturated, it turns to gray.

For more information on lights, see the sections "Hue," on page 4-41, and "Brightness," on page 4-9.

: Note. You can also adjust the saturation of the light using the Attributes Editor, or use (CTRL-L) on Saturation to set the light value numerically.

Scale

Edges, faces, polyhedra, vertices

Scales an element relative to its geometric center or relative to any arbitrary vertex.

(CLICK-L) scales the element relative to its midpoint.

(CLICK-M) scales the element relative to a selected vertex.

(CLICK-R) lets you choose a scaling center with the same options shown in Figure 4.103.

Figure 4.111 Original object and scaled copy

Select Edge Loop

Edges, edge collections

Collect edges and edge collections that are lined up in a single path (e.g., across a grid) or in a loop (e.g., around a solid of rotation). The collection stops when it encounters a vertex with three edges (such as the edge of a grid) or with five or more edges (such as a vertex that branches into a "Y").

This item is useful for selecting all the elements around an object that might otherwise be difficult to collect.

Figure 4.112 Selecting an edge loop

You can then manipulate the selected elements just as if you had collected them manually; additionally, once you have a collection of segments, you may want to use Select Elements to collect the points before performing another operation:

Figure 4.113 Left, collected elements; right, selected elements modified with Scale

Select Elements

All element types

Select all neighboring or otherwise related elements of a single type.

(CLICK-L) selects all points of the selected element.

(CLICK-M) selects all segments of the selected element.

(CLICK-R) selects all faces of the selected element.

Select Face

Edges

(CLICK-L) selects the face to the left of the specified edge.

(CLICK-M) selects faces with two or more edges of the face selected.

(CLICK-R) selects the face to the right of the specified edge.

Note that because this operation selects faces based on their "rightness" or "leftness" that it may be helpful to turn on Highlight Head for Segment Highlighting in the Utilities>Preferences menu.

Select Shared Edges

A collection of faces

Selects those edges which are shared by two or more contiguous faces in a collection.

Set Direction

Infinite lights

Set the light direction (where it's pointing) using numeric xyz coordinates.

: Note. This command appears under the Other Geometric operations portion of the modify operations menu.

Set Light View

Spotlights

Interactively positions the light as if the light itself were the camera's viewpoint. The light moves just like the camera.

1. With Points sensitive in the Elements sensitivity menu, select the light.

The camera view is set to the light's; it is aimed toward the light's aimpoint.

2. Move the mouse until the portion of the scene you want to illuminate with the light is in the N-Geometry window.

Use the camera moves just as if you were moving the camera.

3. (CLICK-L) to save the light's new position.

The camera returns to its previous position, but the position of the light has been updated.

: Note. The aspect ratio for the camera changes to match the aspect ratio of a spotlight with a rectangular spot pattern.
: Note. To abort a light view change, (CLICK-R) after the move has been initiated.

Set Weight

Bspline curve control points

Gives more or less "pull" to a control point. For an arc along a wire, select the segment and convert it to a bspline using the Replace with Bspline command. Then select a point at either end of the wire and move the mouse back and forth to change the shape of the arc.

Figure 4.114 Top, original Bspline curve; bottom, after modifying the "weight" of a control point.

Smooth

Face collections, polyhedra, wires

Gives polyhedra and face collections a smoother, rounder appearance by beveling all edges and vertices. Additional faces are added to smooth the body:

Figure 4.115 Left, original cat; right, smoothed cat

You can smooth a collection of faces if you want to add detail only to a particular area of a body. For example, suppose you wanted to add some detail just to the head area of the cat model shown above:

1. Collect the faces around the cat's head.

2. (CLICK-L) on Smooth.

Only the area made up of the collected faces is smoothed:

Figure 4.116 Left, original cat; right, cat with head region smoothed

To smooth a body using a menu (to specify how many times the Smooth command should be applied), (CTRL-L) on smooth. The menu in Figure 4.117 is displayed:

Figure 4.117 The menu for adjusting smoothing parameters

Iterations specifies the number of times N-Geometry smoothes the object during each smoothing operation. The higher this number, the more faces the object is subdivided into.

Figure 4.118 Left, original pyramid; center, pyramid smoothed once; right, smoothed three times

Copy w/History smoothes a copy of your original object, retaining the original in its pristine (pre-smoothed) condition. The original can then be used as a type of "control" body.

Smoothing with History

The "Smooth with History" technique described here creates a copy of an object; the copy is smoothed a specified number of times, and can be controlled using the lower-resolution original as a "control" object.

Try the following:

1. Create a cube.

2. (SHIFT-L) on the cube.

3. (CTRL-L) on Smooth.

Enter 3 for number of iterations and Yes for Copy w/History?
You now have two copies of the original object, one smoothed once, another smoothed three times.

Figure 4.119 Original cube with copy smoothed three times

4. Choose Points on the Element sensitivity menu.

5. Move a point on the original object.

Figure 4.120 Modified control object

6. Choose Bodies on the Element sensitivity menu.

7. (SHIFT-L) on the smoothed copy.

8. (CLICK-M) on Smooth.

This resmoothes the copy based on the state of the original control object:

Figure 4.121 Move a point on the original control object

When used in conjunction with N-Dynamics, this means that you can create a test animation using the lower resolution object (which will animate quickly), then substitute the higher resolution object when you do you final animation.

You may also find it useful to toggle the visibility or sensitivity of the hi-res version of the object (either (SHIFT-L) on the object or use the Object Display>Visibility command). See the sections "Visibility," on page 6-8 and "Sensitivity," on page 6-7.

Sphericize

Bodies, faces, collections of points

Moves the selected set of vertices equidistantly from a specified point, making the element rounder.

After selecting the object, you specify a midpoint around which the object is to be "sphericized" from the displayed menu.

You are then automatically put in points mode and must select a control point somewhere on the object that will locate the outer radius of a circle that defines the "sphere:"

Figure 4.122 Left, original man; right, sphericized version using object midpoint as center and a point on top of the head to define the sphere's radius

: Note. Selecting a control point closer to the center also has a scaling effect on the object (since it defines a smaller radius). If you want the shape to retain its size, choose a control point close to the perimeter of the object.

Sphericize can also be used to make a face more circular; the effectiveness of this command depends on how many sides the selected face has. Increasing the number of edges on a face provides better (more spherical) results:

Figure 4.123 Left, original face, middle, sphericized face (8 edges), right, sphericized face (16 edges)

Spot Angle

Spot lights

Interactively adjusts the spot angle for the selected spotlight:

Figure 4.124 Left, original light; right, same light with enlarged spot angle

Taper

Polyhedra, wires, wire node collections, vertex collections

Progressively scales the distance between collected elements along an axis.

Figure 4.125 Cat tapered along the Y axis

(CLICK-L) brings up the following menu to select taper parameters:

Figure 4.126 Specifying taper parameters

Scale Factor is the percent to scale the polyhedron along each of its axes. The default is a taper of (1, 1, 1) for the x, y, and z axes, respectively. This default does no scaling. If the values are left at the default, interactive tapering is enabled after you click on Taper. To taper an object symmetrically by A along the y axis, the components factor should be (A, 1, A).

Taper Axis is the global axis that the taper proceeds along. The default is y.
Distance from Center is the reference point on the taper axis at which the polyhedron is or would be tapered the specified angle. The default is the highest point of the polyhedron along the Y axis.
Axis Location is the default is the midpoint of the polyhedron. This center defines two things: taper axis coordinate (the default is y) specifies the start of the taper or the location where the taper = 0. The other two coordinates specify the point through which the taper axis passes.
Scale is the exponential power of the rate at which the taper proceeds. The default power of 1.0 power creates a linear taper. A lower power, such as 0.5, tapers quickly near the center, then more slowly near the ends. A higher power, such as 2.0, tapers slowly at the beginning and then more quickly near the ends.
Symmetric to Center toggles on or off; it determines whether the tapering occurs symmetrically around the center of the object.

Previous resets the axis location values to their previous values (before they were changed in this dialog box).

Tighten

Vertices, bodies, and wires

Pulls extruded parts of an object closer to the surrounding "surface" of the model. This could be used, for example, to tighten a group of mountains that had been pulled up from a grid.

For each selected point, the midpoint of all adjoining faces is calculated; the tighten operation moves the point toward or away from that midpoint.

(CLICK-L) to tighten the selected points by the default factor (.5).

(CLICK-M) to relax the selected points by the default factor (.5).

(CLICK-R) to bring up a menu that allows you to specify how the object is tightened (or relaxed):

Figure 4.127 Tighten parameters

Tightening factor specifies how much the point is moved toward the midpoint of the surrounding faces.
Hardness Weight determines how objects are tightened. A higher value tries to preserve "sharp" edges.
Displacement Name lets you save the tightened/relaxed object as a relative displacement.
Outside Neighbors specifies whether the vertices along the perimeter of the selected group of vertices are selected for the operation.

Figure 4.128 Left, original object; right, with individual vertices loosened or tightened

The Tighten operation can be applied to an entire group of vertices, such as the peaks of a range of mountains:

Figure 4.129 Left, original object; right, with peaks selected and tightened twice

: Note. Tightening an entire grid (like that in Figure 4.129) rather than points on the grid can cause the entire object to shrink (since all selected points are tightened. Tighten is best used with an explicitly selected set of vertices.