File and Edit Menus (cont.)

Solid of Rotation

A solid of rotation is an object created by sketching the silhouette of the desired object from top to bottom, then sweeping that silhouette around either the vertical or horizontal axis to describe the object.

Figure 2.35 Typical solid of rotation (created with wire shown at right)

Note! The silhouette should lie entirely to one side of the axis of rotation so that the generated solid of rotation does not intersect itself.

Tube

A tube is a polyhedron created by sweeping a cross section along a path defined by a wire or sketched contour. The cross section can be automatically generated, radially symmetric (circular), drawn by hand, or derived from a pre-existing wire.

Figure 2.36 Tube parameters

Note that these sketching parameters are the same ones used when creating a tube solid, lamina, or contour solid. The procedures for creating each of these types of objects appear below.

• Circular automatically generates a round cross section for the tube.

Figure 2.37 A wire (top) and a tube made with a circular cross-section

• Arbitrary gives you the option of sketching a cross section or using a previously created wire as the cross section.

To create a tube with an arbitrary shape cross section, encode a second wire that you are going to move along the path.

Figure 2.38 A second wire encoded for use as the contour

(CLICK-R) on Tube to select the path along which you want to pass the cross-section.

Then choose a cross section of type Arbitrary and specify that the cross section is to come from a Previous wire. (CLICK-L) in the C.S. object text box to select the cross section wire to move along the path wire:

Tube Solid

To build a tube solid, start by encoding the contour wire:

Figure 2.40 The contour wire

Next, sketch the path wire. Make sure that the silhouette wire is perpendicular to the path wire. (If you sketch the wire, you can use Rotate to make it lie in the correct plane). Give the wires descriptive names (such as "silhouette" and "path") so you know which wire you are using when executing the solid:

Figure 2.41 The contour and path wires

Note. The path wire should lie on a single plane; otherwise the generated top and bottom faces of the tube are likely to be twisted.

Next, (CLICK-R) on Tube Solid. You are prompted to select the path wire. In the dialog box that opens, choose Previous, then specify the contour wire to pass along the path in the Contour object text edit box.

The tube solid parameter menu

Imagine that the contour wire defines half of a shaper bit moving along a solid defined by the height of the contour wire:

The contour wire moves along the path wire, much like a bit

Contour Init Rot determines the initial angle or rotation at which the bit is "applied" (the default of 0 keeps the bit perpendicular). The resulting tube solid looks like this:

The contour passes along the path wire; faces are created along the top and bottom of the path to create a tube solid

Lamina

Figure 2.42 Wire

Figure 2.43 Wire converted into lamina and extruded

Contour Solid

Figure 2.44 How the contour and cross section combine to form a contour solid

Next, create the wire that you'll use as the contour solid. If you create it ahead of time, you'll need to rotate it so it's perpendicular to the path wire:

Figure 2.45 Path and cross-section wires for contour solid

Next, (CLICK-R) on Contour Solid. You are prompted to select the path wire. In the dialog box that opens, choose Previous wire, then specify the cross section to pass along the path in the C.S. object text edit box.

Figure 2.46 Contour solid menu parameters

(CLICK-L) on Make Solid to generate the final contour solid:

Figure 2.47 Finished contour solid

Wires & Trajectories

• Wires are useful for building skeletons and defining the path of tubes and other similar polyhedra.
• Trajectories are wires that are used as animation paths. In N-Dynamics, you can animate an object (or the camera) along trajectories.

When encoding wires or trajectories, mouse clicks work as follows:

Table 2.3 Mouse behavior when encoding wires

Mouse action	Description
(CLICK-L)	Creates a new point.
(SHIFT-L)	Acts differently depending on the type of object being encoded: For a polyhedron, it connects a line to the nearest old point (which is highlighted). For a wire, it undoes the last segment.
(CTRL-L)	Creates a new control point for a nurb curve.
(ALT-L)	Starts an arc.
(HOLD-M)	Adjusts the location of the cursor in the z axis.
(CLICK-R)	Acts differently on the type of object being encoded: For a polyhedron, it closes the current face by creating an edge between the last and first vertices. For a wire, it finishes the operation.
(SHIFT-R)	Displays the Encoding Options menu, which is how you exit from encoding mode.
(CTRL-R)	Halts encoding temporarily to let you execute one N-Geometry command before returning to encoding. (This is useful for moving the location of the camera.)

Encoding Options

Figure 2.48 Encoding Options menu

Cursor

Figure 2.49 Setting cursor parameters

• Cursor type lets you specify the type of cursor you want to use:


• Crosshair selects a default crosshair cursor.

  

Figure 2.50 Crosshair cursor

• Locator box selects one of three alternate cursors, described below.

  The locator box cursor shows where the cursor is in three dimensional space by drawing a box to connect the cursor with the x, y and z axes. You can set the overlap length, analogous to the crosshair length and the box style. There are three types of locator boxes:

  
  
  • 3-arm locator box (shown in Figure 2.52) draws a line from the cursor to the intersection of each of the three planes:

    

• Half box draws a box that defines the space between the current cursor position and the global origin:

  

• Full box is similar to the half box locator, except that the path of the wire is shown from the last point on the wire to the cursor position:

  

• Crosshair Len specifies the length of the three crosshairs.
• Crosshair Gap sets the gap distance between the positive and negative arms of the cursor's axes.
• Cursor speed sets the relative speed of the cursor (higher values move the cursor faster, with a default of 0.2).

Quit

Temporary Halt

Zero

• (CLICK-L) resets the cursor to x=0.

  
  

• (CLICK-M) resets the cursor to y=0.

  
  

• (CLICK-R) resets the cursor to z=0.

Patch bodies are better at representing smoothed surfaces because it uses curves to describe a surface rather than polyhedra; and because patch bodies are described by curves, you can render an object at essentially any distance from the camera with no appreciable change in quality.

To create a patch body:

1. Create a polyhedron (such as an octahedron).

Because patch bodies work better for smoother objects, you may want to use the Smooth operation on any object for which you generate a patch body.

2. (CLICK-L) on File>New Object>patch body.

You are prompted to select the control object from a list of objects that currently exist in the scene.

The generated patch body approximates the shape of the polyhedron, but is a lighter gray (if you are using the default color scheme).

To change the shape of the patch body, you manipulate the controlling polyhedra (or other N-Geometry object).

Grid

Figure 2.56 Grid parameters menu

Parameters for generating a grid are shown below:

Table 2.4 Grid parameters

Parameter	Type	Description
Name		The name of the grid object.
Width & Height		The overall dimensions of the grid, expressed in global units.
Orientation		The axis to which the plane is perpendicular.
Intervals		Number of faces the grid should be divided into on the given axis.
Body type		Type of grid to generate.
	Polyhedron	Generates an object whose "front" or top side is divided into the specified number of faces. (The back side remains a single face unless manually cut.)
	Rectangular Mesh	Generates a mesh; that is, the apparent grid is actually a group of joined segments with no faces. This is much like a net. The rectangular mesh grid looks like a polyhedral grid but has only nodes and segments, as does a wire. The grid has no faces and has a constant number of segments in either dimension. For example, if you cut one of its segments, a rectangular mesh grid automatically cuts all the other segments in that row in an identical fashion. Note. You can make a splined surface grid from a rectangular mesh by selecting the mesh, then choosing the Make Splined Surface command. (See "Make Splined Surface," on page 4-60.)
	NURBS Sheet	Generates a non-uniform rational B-spline (NURBS) mesh. The mesh functions much as a control polyhedron when working with a patch body. NURBS sheets are useful in that the curved surface can be manipulated directly. If you create a NURBS sheet, Degree specifies the method used to generate the splined surface (the lower the number specified, the more closely the spline surface follows the polyhedral surface): A degree of 1 causes the splined surface to match the polyhedral surface exactly, and is the most calculation intensive. A degree of 2 calculates the splined surface using a quadratic calculation. (This method requires at least 3 point on each side of the grid.) A degree of 3 calculates the splined surface using a bicubic calculation (This method requires at least 4 points on each side of the grid.) Figure 2.57 A polyhedral grid

Text

Selecting File>New Object>text brings up the Select 3D Text Parameters menu. If you don not have the Logo Utilities Item selected in the Utilities>Preferences menu, only a subset of the items on the following menu will appear:

Figure 2.58 3D text parameters menu

When you create a text string, N-Geometry creates a separate object for each character; each "character" object is automatically restructured under the "word" object.

Figure 2.59 Structure for word object-each letter is a subobject under the word object

This gives you the ability to animate either the word or individual characters when animating in N-Dynamics.

Table 2.5 Text parameters

Parameter	Subparameter	Description
Object Name		The top-level name of the text object.
Characters		The characters to create. Each character is a separate body and is inferior to the top-level text object.
Font		Character font. The default font is the first available loaded font, if any. (CLICK-L) and choose New to select the font to use when generating the text.
Font Height		Specifies the font height (in global units).
Kern chars?		Compensates for wide and narrow characters by setting extra space around wide characters and setting less space around narrow characters.
Letter-spacing%		Adjust the amount of space between all characters as a percentage of the font height.
Curve Smoothness		The factor to determine subdivision of arcs along the edge of a letter
Centered?		Centers the created text string around the object's center.
Remove holes?		Automatically deholes any faces. See "Dehole," on page 4-25 for more information.
Extrude depth		The "depth" of the created text characters, expressed in global units.
Bevel Width		Creates beveled letters. Selected edges (specified with Bevel which? below) are "sanded down"by the amount specified here (in global units). A higher value bevels the edge more.
	Hardness	Specifies the hardness of edges to be selected (perpendicular edges have a hardness of 90 degrees. Higher values select edges closer to perpendicular.
	Bevel which?	Specifies which edges are beveled: Front bevels only those edges on the front of the letter. Back bevels only those edges on the back of the letter. Both bevels edges on the front and back. Any bevels edges on the front, back, and any edges created when the letter is extruded (if any new edges are created).
Coplanar width		Create coplanars around the edges of the letter. The edges (specified below) are coplanared by the amount specified here (in global units).
	Hardness	Specifies the relative "harshness" of the coplanaring effect.
	Coplanar which?	Specifies which edges are coplanared: Front creates coplanars along the edges on the front of the letter. Back creates coplanars along the edges on the back of the letter. Both creates coplanars along the edges on the front and back. Bevels Only creates coplanars only on beveled edges. Bevels & Any creates coplanars on beveled, front, back, and any edges created with an extrude operation. Any creates coplanars on any edges except those created as a result of the specified bevel.

Default generated characters are laminae and can be manipulated just like any other object. However, the number of operations you can use with faces with holes is limited. (Refer to the section "Faces with Holes," on page A-1.)

Figure 2.60 Some sample text

Image

To use this operation:

1. In N-Paint, make the image from which you want to generate the object(s) your current image.

Figure 2.61 Make the image you want to generate the laminae from the current image

2. In N-Geometry, (CLICK-L) on File>New Object>Image.

The following dialog box appears:

3. After selecting the parameters used to generate the laminae, (CLICK-L) on the Make Body button.

(The parameters on this menu are described below.)

The parameters in the Image dialog box are described in the table below:

Table 2.6 Parameters for generating objects from an image

Parameter	Type	Description
Object Name		The name of the generated object.
Source		Source for the generated object.
	Canvas	Uses the RGB channel of the currently selected image.
	Canvas Matte	Uses the matte channel of the currently selected image.
Threshold		The minimum value the pixel for the value to be used in generating the lamina or wire. Lower values will select more of the image.
Min feature size		This option is useful if the image (or matte) contains "spots" or other small painted areas that would generate very small objects. Objects smaller than the specified size are not generated.
Reduction Flatness		How closely the shape of the generated outline will match the original (the value can be interpreted as maximum deviation from the raw data). A larger number will allow more latitude for combining a lot of short segments into one longer segment. This not only reduces the amount of data, making the result easier to select for editing, but since images are typically a little noisy anyway, also helps to smooth out the outline.
Size		The size (in global units) that the object will be.
Sizing Reference		What you use to determine how the object's size. Either the object itself (after it has been extracted from the image), or the image boundary. If you are doing several extractions from the same or related images that requires registration between the objects, the latter is the way to go.
	Object	Gives you an object exactly the size you requested, but at an unknown scale factor and offset.
	Image	Gives you a predictable scale factor but the object's size varies with its size in the image.
Body Type		Whether the generated object should be a polyhedra (typically a lamina) or a series of connected wires.
	Polyhedron	Generates a polyhedron.
	Wire	Generates a wire.

Skeleton

Figure 2.64 A skeleton primitive

To create other skeleton primitives, (CLICK-L) on GeoMenus>File>New Object, then (CLICK-R) on Skeleton. The following types of skeletons can be generated:

• Horse skeleton
• Six legged skeleton (insect)
• Eight legged skeleton (spider)
• Hips (a good way to start a custom humanoid skeleton!)

Figure 2.65 New skeleton primitives; clockwise from upper left: hips, horse, eight-legged, and six-legged

For more information on using skeletons, see the Skeletal Animation System Reference Guide and the Skeletal Animation System Tutorial.

(CLICK-L) on [Next] to continue...

Copyright © 1996, Nichimen Graphics Corporation. All rights reserved.