Cull XGen primitives

You can remove hair, fur, or instanced primitives from previews and renderers by using different culling methods. Culled primitives can be displayed in a highlighted color in the preview. Culling can be undone.

Cull primitives using the Cull Selected Primitives tool

1. Access the Select Primitives tool by clicking this icon in the XGen Editor toolbar.
2. Select the primitives you want to cull by:
   • Dragging across the primitives to select one or more primitives in an area.
   • Shift-drag to select one or more primitives in multiple areas.
   • MMB-drag across the primitives to inverse select one or more primitives in an area.

   The primitives to be culled display green: .

3. Click Cull Selected Primitives: .
4. (Optional) In the Culling section of the Primitives tab, turn on Display Culled Primitives.

   The culled primitives display red: .

Cull primitives outside of the view

You can automatically cull primitives that face away from the camera or appear outside of the preview and rendered frames. Removing primitives that do are not visible in the final frames can save rendering time.

1. In the Culling section of the Primitives tab, turn on Enable Culling.
2. Turn on the following culling options:
   • Cull Primitives on back faces to remove primitives that face away from the camera
   • Cull Primitives outside the view to remove primitives that do not appear in the region of the camera frustum.
3. (Optional) Turn on Display Culled Primitives.

   The primitives culled by these methods display blue: .

4. Set Padding Angle for each culling option. See XGen Culling attributes.

Cull primitives using an expression

You can use expressions to cull primitives. For example, you can create an expression that culls primitives with specific lengths. By default, a place holder culling expression is connected to the Cull Expr slider control. You can create a new expression to

1. In the Culling section of the Primitives tab, turn on Enable Culling.
2. Click this icon to edit the culling expression in the XGen Expression Editor.
3. XGen Expression Editor, delete the default expression and then type the following:

   $Length=4.00;#0.00,10.00

   $cLength < $Length ? 0 :1

   This expression compares the set value, ($length) to the primitives calculated length ($cLength) and when the $cLength is greater than 4, the primitive is culled.

4. Adjust the Cull Expr to set a value for the expression.
5. (Optional) Turn on Display Culled Primitives.

   The primitives culled by an expression display purple: .

Uncull primitives

Use the Select Primitives tool to select and uncull primitives previously culled by the Cull Selected Primitives tool or by an culling expression. By default, a place holder culling expression is connected to the Cull Expr slider control.

1. Ensure Display Culled Primitives is on.
2. Use the Select Primitives tool to select the culled primitives.

   The selected primitives display yellow: .

3. In the Culling section, click Uncull.