Weight Maps

About Weight Maps

Weight maps are properties of point clusters on geometric objects. They associate each point in a cluster with a weight value. Each cluster can have multiple weight maps, so you can modulate different parameters on different operators in different ways.

Weight Map Operator Stack

Each weight map has its own operator stack. When you create a weight map, a WeightMapOp operator sets the base map, which can be constant or one of a variety of gradients. Then when you paint on the weight map, the strokes are added to a WeightPainter operator on top of the WeightMapOp in the stack. Like other elements with operator stacks, you can freeze a weight map to discard its history and simplify your scene data.

Weight Map Limitations

Weight maps have certain limitations:

You can apply a weight map on a curve, but you cannot display it or paint on it. You can use the constant or gradient base map generated by the WeightMapOp operator, or set values using an ICE tree (see Weight Maps in ICE).
You cannot animate paint strokes.

Weight Map Workflow

This section presents a quick overview of the workflow for using weight maps. The sections that follow later in this chapter will fill in the details.

Start with an object.
Optionally, select some points or a cluster.
Apply a weight map using Get Property Weight Map
Press W to activate the Paint tool, then use the mouse to paint on the weight map.
Connect the weight map to drive the value of a parameter — for example the Amplitude of a Push deformation.
You can reselect the weight map and continue to paint on it to modify the effect further.

Creating Weight Maps

When you create a weight map, a WeightMapOp operator is applied. This operator creates the base weight map, which can be a constant value or a gradient.

To create a weight map

Select the element to which you want to apply a weight map:
- If you select a cluster, the weight map will be applied to it.
- If you select an object, a cluster will be created for all the points on the object and the weight map will be applied to the cluster.
- If you tag (select) points, a cluster will be created and the weight map will be applied to the cluster.
  
  NoteYou can improve performance greatly by using small, localized weight maps on specific points rather than on the whole object or large areas. This is especially true if most of the points would have been weighted to zero anyway.
Choose Get Property Weight Map from any toolbar. A weight map is applied and its property editor opens.

To see your weight map while you are setting options, you can either change your view settings as described in the next section or press W to activate the Paint tool and move the mouse pointer over a 3D view.
Set the options you want for your base map on the Weight Map Generator page. For example, if you set the Weight Map Type to Constant and the Base Weight to 0, you start with a blank map for painting weights. You can also choose from a selection of linear and radial gradients, and set other options.

When you create a weight map, it is automatically selected so you can immediately paint on it as described in Painting Weights or apply a deformation as described in Deforming with Parameter Maps.

You can connect a weight map to drive a parameter as described in Connecting Maps.

Displaying Weight Maps

Weight maps are visible in the 3D views when certain display options are on. You can set these options manually using the procedure below.

Note that these display options are also temporarily toggled on when the Paint tool is active and you move the mouse pointer over a 3D view. When this happens, the previous display settings are automatically restored when you exit the Paint tool. You can also turn off Show Property Map in the Brush Properties Property Editor to hide the map except while you are painting a stroke.

To display weight maps in a geometry view

Click on the Display Mode menu, and set it to Constant or Shaded. Constant mode shows the weight maps more clearly than Shaded.
Click the eye icon on the menu bar to make sure that Weight Maps is on.

For other ways of setting this and other display options, see Displaying Types of Elements and Other Data [Basics].

Selecting Weight Maps

Weight maps are stored under the clusters to which they belong.

To select a weight map

Select the object.
Choose Explore Property Maps from the Select panel. A pop-up explorer opens.
Select the desired weight map by clicking on its name.

Painting Weights

To paint weights, you first activate the Paint tool. You can then add weight, remove weight, smooth weights, or change the brush radius, opacity, and other brush properties.

Overview of Painting Weights

This section provides a quick overview of painting weights on weight maps. Each step is described in more detail in the sections that follow.

Select the weight map. If you omit this step, painting is performed on the last active weight map by default.
Activate the Paint tool by pressing W. For additional ways to activate the Paint tool, see Activating the Paint Tool.
If desired, adjust the brush properties:
- Press R and drag the mouse to change the brush radius interactively. You can also set the radius on the weight paint panel. For additional ways to set the radius, see Changing the Brush Radius.
- Press E and drag the mouse to change the opacity interactively. The opacity controls how much weight is added with each stamp of the brush.
- Set other options in the Brush Properties Property Editor (Ctrl+W).
Click and drag to paint. In normal (additive) paint mode:
- To add weight, use the left mouse button.
- To remove weight, either use the right mouse button or press Shift while using the left mouse button.
- To smooth weights, press Alt while using the left mouse button.
For more information about painting, see Using Brush-based Tools.

Tips for Painting Weights

Here are some quick tips to consider when painting weights:

To paint weights on a subdivision surface created with the geometry approximation method, click the eye icon (Show menu) on a 3D view's menu bar and make sure that Polymesh Hulls is on.

To see the weight maps on the hull, make sure that Subdivision Surfaces is off.
When painting, you can increase performance by reducing the object's geometry approximation settings. The Paint tool uses the triangulation of the object to follow its surface. See Applying and Editing Geometry Approximation.
You can set the paint mode and certain other brush properties on the weight paint panel. However, the weight paint panel is designed for use with envelope weights and most of its tools are not useful for weight maps.

Setting Weight-Map Properties

You can modify weight-map properties. For example, you can change the name or display color — this is useful if you need to easily distinguish between several weight maps on the same cluster.

To display a Weight Map property editor

Select the object.
Choose Explore Property Maps from the Select panel. A pop-up explorer opens.
Click on the icon of the weight map.
Set the options to change the weight map name or display color.

Freezing Weight Maps

Weight maps can be frozen to simplify your scene's data. Freezing collapses the weight map generator (the base constant or gradient map you chose when you created the weight map) together with any strokes you have applied.

After you have frozen a weight map, you can still add new strokes but you cannot change the base map or delete any strokes you performed before freezing.

To freeze a weight map

Select the weight map.
Click the Freeze button on the Edit panel.

Weight Maps and Symmetry

You can paint weights symmetrically using symmetry maps, an object's local center, or both.

Applying Symmetry Maps

You can apply different symmetry maps on different clusters on your object, allowing you to have different planes of symmetry in different areas.

To apply a symmetry map

Select an object, cluster, or points.
Choose Get Property Symmetry Map from any toolbar. A property editor opens.
On the Symmetry Map Generator property page, set the Symmetry Plane to the desired value: YZ (X = 0), XZ (Y = 0), or XY (Z = 0).

The symmetry map uses the object's local center and the chosen plane to establish a correspondence between points.

Brush Options for Symmetry

To set the brush's symmetry options

Open the brush's property editor (press Ctrl+W).
Set the options on the Symmetry Options tab:
- Use Local Object Symmetry Plane uses the object's local center and whichever symmetry plane is currently active to determine symmetry. To set the active symmetry plane, right-click on Sym in the Transform panel and choose an option.
- Use Symmetry Maps uses any symmetry map applied on the object to determine symmetry.
- If both options are on, symmetry maps take precedence. This allows you to symmetry maps wherever they exist and the object's local symmetry plane wherever there are no clusters with symmetry maps.

Activating Symmetrical Painting

You can activate Sym to paint symmetrically.

To activate or deactivate symmetry

Click Sym on the Transform panel.

To set the local symmetry plane

Do one of the following:

Right-click on Sym and choose YZ, XZ, or XY.

or
Right-click on Sym and choose Symmetry Properties, then set Symmetry Plane to the desired value in the Symmetry Options property editor.

Editing Weight Maps Numerically

You can edit weight maps numerically using the weight editor. The weight editor can be used for both weight maps and vertex colors as well as envelope weights.

Displaying the Weight Editor

Select one or more objects with an envelope, weight map, or vertex color property.
Choose View Animation Weight Editor or press Ctrl+E.

Editing Weight Maps with the Weight Editor

A	Sets the weight of selected cells. Values are affected by the weight edit mode (N). If multiple cells with different values are selected, the slider is blank but you can still use it to affect all values in the same way.
B	Right-click to sort by value.
C	Multiple weight maps and their map colors. Double-click to expand and collapse, or right-click for more options. Double-click the first vertical splitter line to resize the first column to autofit the property names.
D	Points are listed in rows. Click the row label to select, or right-click to sort or access other options. Drag a row border to resize.
E	Each cell in the table shows the weight value for that point. To set any cell's weight directly in the table, right-click in the cell and type a value.
F	Selected cells are highlighted. To select a cell, click it. To select a rectangular range of cells, click and drag across them. Alternatively, click to select the first cell and then Shift-click to select the last cell. To add a cell to the selection, Ctrl+click it. To add a range of cells to the selection, Ctrl+click and drag across them. Alternatively, Ctrl+click the first cell and then Ctrl+Shift+click the last cell.
G	Use the File menu to save or load presets. You can load a preset only if the number of points is the same as the current weight map. The options on the Edit and View menus are also available directly on the toolbar.
H	Locks the view to the currently displayed elements.
I	Forces the view to update when it is locked. Alternatively, you can press F6.
J	Clears the view.
K	Transfers the cell selection to 3D views.
L	Freezes the weight map's operator stack.
M	Controls the display of points in the table: Show shows just the selected rows and hides everything else. Show All shows all rows. Focus automatically shows the rows of the points that you select in the 3D views. Filter automatically hides zero-weighted points when you select points in the 3D views. Highlight automatically highlights points in the 3D views when you select cells.
N	Weight edit mode: Abs sets the weight of selected cells to the value of the slider. Add adds or subtracts the value of the slider to or from the selected cells. Add % adds or subtracts the value of the slider as a percentage of the selected cells' current values. Normalize does not apply to weight maps.
O	Select an envelope weight property, weight map, or vertex color property to edit.