Action Centers are a definable origin position for modeling and transform actions in modo. While other 3D software programs use the fixed mesh geometry pivot point as the center for most actions, modo separates the Action Center into an independent dynamically definable component. This provides users a means to easily change the positions from where the action of any tool originates from. Action Centers can be activated directly in the interface in the Action Center drop down menu or within the menu bar under "Edit > Action Center". If the user wishes, the Action Center can be further broken into its 'Center' and 'Axis' components for even greater control.
Generally user won't see anything happen within the 3D viewport when selecting an Action Center until a tool is made active, as actions centers themselves are represented by the positions of an active tools handle. When users select a new Action Center, the position and orientation of the handle will update to reflect the new axis and center.
Action Center Types
None
When no action center is selected,
modo defaults to none, which is essentially the same as Automatic, except there is no ability to explicitly define the axis.
Automatic
When a tool is activated, the 'Automatic' action center positions the tools handle at the center of the current selection (or on all active geometry in the case of no selection) with the axis aligned to the world or Work Plane axes. Users can explicitly select the axis in the properties panel and interactively modify it by adjusting the orientation handle, the thin blue line with the yellow dot. The 'Automatic' Action Center is not fixed like others Action Centers are. Users can define a new center by LMB+clicking away form the tools handle, setting the positions at the intersection of where the pointer clicked in the viewport and the Work Plane.
Selection
'Selection' bases the action center on the average vertex position of the selection in the 3D Model View effectively centering the action center to whatever is selected. Setting the Action Center to Selection will change the tool's handles to have the center and axis aligned to the current selection.
Selection Border
This action center preset combines the Selection Border center with the Selection based axis. This combination centers all tool handles around the border, or boundary, of the selected elements with the orientation of the tool derived from the average normals of all selected elements. The border of selection is defined by the “open edge†area where the selection stops. This is extremely useful for posing character type operations. Selecting a loop of polygons at say, an elbow, using the Select > Close loop command to select the rest of the arm, and activating 'Selection Border' will position a rotate transforms handles aligned to the initial loop selection making it easy to 'bend' the arm.
Selection Center Auto Axis
Selection Center Auto Axis keeps the center of the tool handles centered on the geometry, but realigns the tool handles to the major axes. Selection Center Auto Axis provides an Axis field in the Tool Properties Action Axis Auto section, so you can easily change from one axis to another by clicking the appropriate button.
Element
Setting the Action Center to Element allows you to click on any element in the 3D model to set the action center. If you click on one polygon, modo realigns the tool's handles to its normal. If you click on an edge, or a vertex, modo also aligns the tool handle to the normal of those elements. If you want to Stretch an entire model along the normal of any particular polygon , for example, you simply activate the stretch tool, click on the polygon and now you can scale along that axis.
Element Action Center does not require the element that is selected to be the element that is used for the Action Center. Once you have a polygon selected, you can choose Element Action Center, then click on a different polygon. That polygon will be the reference Action Center for transforming the original selected polygon.
Screen
Screen Action Center allows the action center and axis to be based on the frame of the viewport, or Screen space. When Screen Center and Axis is chosen for any transform, the tool handles will realign themselves to the screen, and the transform becomes in relation to the "picture plane" rather than to any world or local coordinate system.
Origin
The 'Origin' action center uses the world coordinates 0,0,0 for the center of any transform, regardless of item or element position. While less useful with the Move transform, this is handy for Rotate or Stretch if you are building something off the origin to begin with. You can easily rotate around the center of the 3D View using this setting. It also makes it easy to accurately set functions like mirror that require they happen across the origins planar axes.
Parent
The 'Parent' action center uses the pivot position of the parented item (as opposed to the center position). Useful for transforming items in a hierarchy when you wish to keep items in proper relationship to their parents.
Local
The 'Local' action center uses the center of individual element clusters for the operation center, effectively like having a separate axis and center for each selection group. This lets you select multiple elements and have them each rotate around their own local axis. When using the Move tool, the handles are axis-aligned to the last selected polygon. This is particularly useful when working with edges as you can use the stretch tool to scale several edges simultaneously along each ones individual local axes.
Pivot
The 'Pivot' action center uses the pivot position of the item as the center of any transform. This is especially useful for animated items that might not currently near the origin center.
Pivot Center Parent Axis
The 'Pivot Center/Parent Axis' action center uses the current items pivot position as the center, but adjusts the axis to match the parent item.
