Scaling Objects

Scaling changes the size of an object. Unlike translation and rotation values which are absolute, scaling values are multipliers. A cube created at a length of 5 and scaled with a factor of 2 has a length of 10. Negative scaling turns an object inside-out.

When an object is created, its scale is automatically set to 1.0.

To scale objects

1. Select the objects to scale.

2. Activate the Scale tool by doing one of the following:

- Press X.

or

- Click the s button on the Transform panel.

3. If necessary, change any options:

- The scaling modes control which axes the object is scaled along. For a description of each mode, see Scaling Modes.

- You can restrict the scaling to specific axes. See Specifying Axes.

- Activate COG to scale about the center of geometry.

Alternatively, set the pivot manually as described in Setting the Pivot. When scaling, the pivot defines the center of scaling. For more information about this, see Setting the Center of Scaling.

4. Scale the objects using the mouse in the 3D views:

- If you are using the SRT manipulators, click and drag on different parts (handles) of the displayed transformation axes to scale the objects in different ways.

For general information about the SRT manipulators, see Transforming Interactively with the SRT Manipulators. For specific information about the Scale manipulator, see Using the Scale Manipulator.

- If you are not using the SRT manipulators, click and drag the mouse anywhere in the 3D views.

The function of the left, middle, and right mouse buttons depends on the tool, mode, and other options — check the mouse/status line at the bottom of the main window for details. You can also drag while pressing multiple mouse buttons simultaneously.

Scaling Modes

For objects, there is only one coordinate system used: Local. This is because objects are always scaled along their own local axes. Uni and Vol are actually modifiers that change the behavior of the scaling somewhat, but do not change the axes. When the Scale tool is active, you can set these modes using the buttons below the SRT boxes on the Transform panel.

 

Scaling Modes

For components, there are more scaling modes. See Transforming Components and Clusters [Modeling and Deformation Basics].

Local

Local mode scales objects along their local axes. If both Uni and Vol are off, you can use the mouse buttons to scale along each axis independently.

 

Uni

Uni, or uniform, mode scales along all active local axes at the same time with a single mouse button. This avoids the annoyance of trying to drag the mouse while pressing two or three buttons (if you’re not using the manipulators). You can activate and deactivate axes as described in Specifying Axes. You can also temporarily turn on Uni by pressing Shift while scaling.

 

 

When using manipulators to scale in Uni mode, the mouse pointer does not reflect all the axes that are affected. This is because the direction in which you must drag the mouse depends on which axis the pointer is over.

Vol

Vol, or volume, mode scales along one or two local axes, while automatically compensating the other axes so that the volume of the object’s bounding box remains constant.

 

Using the Scale Manipulator

When using SRT manipulators to scale, there are seven handles that you can click and drag:

 

A

Click and drag on a single axis to scale along it.

Double-click to toggle between a single active axis and all three axes, or Shift+double-click to toggle activeness of a single axis (If Allow Double-Click to Toggle Active Axes is on in Transform preferences).

B

Click and drag along the diagonal between two axes to scale both those axes uniformly.

This behavior is affected by Translate/Scale Interaction Style in your Transform preferences.

C

Click and drag the center left or right to scale all active axes uniformly.

In addition to dragging the handles, you can:

• Middle-click and drag anywhere in the 3D views to scale along the axis that most closely matches the drag direction.

• Click and drag anywhere in the 3D views (except on the manipulator) to perform different actions, depending on the setting for Click Outside Manipulator in the Tools > Transform preferences. See To choose the behavior when clicking outside of the manipulators.

• Right-click on the manipulator to open a context menu, where you can set the manipulation mode and other options.

For information about using the SRT manipulators in general, see Transforming Interactively with the SRT Manipulators.

Setting the Center of Scaling

There are several possibilities for the center of scaling — the position that points move away from or towards as you scale up or down:

• By default, the object pivot is the center of scaling. The object pivot is normally the same as the object’s center, but you can change it and even animate it as described in Working with Object Pivots.

• If Pivot Control - Active is off on the Pivot tab of the object’s Local Transform property editor, the object scales about its center rather than its object pivot. Usually, an object’s center is located in the middle of its geometry. However, this is not always the case, particularly if you freeze the transformations or manipulate the center directly. This has an effect on how the geometry appears to move when scaled, even if the center does not actually move.

 

 

Center inside object

Center outside object

When COG is on in the Transform panel, objects scale about the center of geometry (the average position of all points). You can also use COG to scale multiple objects about their common center of geometry. The COG option takes precedence over the object center and the object pivot. Be aware that object centers may move if you scale with COG on.

 

 

COG off

COG on

• You can temporarily change the center used for scaling interactively as described in Setting the Pivot. The tool pivot takes precedence over all other centers of rotation.

Shearing (Scaling Orientation)

You can shear an object by changing the orientation of the axes used for scaling. This distorts the shape of the object when you scale it.

 

To shear by scaling

1. Open the object’s Local Transform or Global Transform property editor. It makes no difference which one you use because they share the same shearing values.

2. On the Scaling tab, set the orientation of the axes used for scaling by modifying the Scaling Orientation (Shear) X, Y, and Z values. These are angular offsets from the object’s local axes.

3. Scale the object in one or more axes. Note that there is no shearing effect if you scale uniformly.

Hierarchical (Softimage) Scaling versus Classic Scaling

Hierarchical (Softimage) scaling uses the local axes of child objects when their parent is branch-selected and scaled. This maintains the relative shape of the children without deformation.

When the hierarchical scaling option is turned off, the result is called classic scaling — children are scaled along their parent’s axes and may be sheared with non-uniform scaling. Classic scaling is recommended if you are exchanging data with other applications, such as game engines, motion capture systems, or 3D applications that do not understand Softimage scaling.

 

A

Parent (left) and child (right) branch-selected before scaling.

B

Scaled in Y using hierarchical scaling: the child is scaled along its own Y.

C

Scaled in Y using classic scaling: the child is scaled along the parent’s Y resulting in shearing.

You specify which method to use for each child in its Local Transform property. You can also set the default value used for all new objects.

To specify hierarchical or classic scaling

1. Select one or more child objects and open their Local Transform property editor.

2. On the Scaling tab, turn Hierarchical (Softimage) Scaling off or on. If it is off, classic scaling is used.

To set the default scaling mode used for all new objects

1. Open the Preferences window by choosing File > Preferences from the main menu bar.

2. Click General.

3. Toggle Use Classical Scaling for Newly Created Objects.

How Hierarchical and Classic Scaling Work

This section describes the technical details of hierarchical versus classic scaling, in case you need to write converters or process transformation data in the same way as Autodesk Softimage.

This notation...

Represents this...

M

A matrix.

V

A vector.

g

A global transformation.

l

A local transformation

scl

Scaling.

sco

Scaling orientation (rotation used to represent shearing).

rot

Rotation.

trs

Translation.

mat

The full transformation matrix.

Hierarchical scaling

Suppose that object B is the direct child of object A, and define the following:

 

 

 

is the standard translation matrix constructed from the vector as follows:

 

For hierarchical scaling, the global transformations of B can be calculated recursively as follows:

 

 

Hierarchical scaling cannot be represented as a simple matrix product because of the way is computed.

Classic scaling

Again, suppose that object B is the direct child of object A. For classic scaling, the global transformations of B can be calculated recursively as follows:

 



Autodesk Softimage 2011 Subscription Advantage Pack