SoTransformManip is the base class for all SoTransform nodes that have a built-in 3D user interface. Since it is derived from SoTransform, any changes to its fields result in the rotation, scaling, and/or translation of nodes that follow it in the scene graph.

Typically, you will want to replace a regular SoTransform with an SoTransformManip (as when the user selects an object to be moved), or vice versa (as when the object is deselected, and the motion interface should go away). Use the replaceNode() method to insert a manipulator into a scene graph, and the replaceManip() method to remove it when done.

Every subclass of SoTransformManip utilizes a dragger of some sort to provide a 3D interface. (This class does not have dragger; but all the subclasses do.) However a manipulator differs from a dragger; it influences other objects in the scene because, as an SoTransform, it alters the state. The fields values and movement of a dragger, on the other hand, affect only the dragger itself.

Each SoTransformManip subclass utilizes its dragger by adding it as a hidden child. When an action is applied to the manipulator, such as rendering or handling events, the manipulator first traverses the dragger, and then the manipulator adds its transformation matrix to the state. When you click-drag-release over the manipulator, it passes these events down to the dragger, which moves as a result ("I can't help it, I'm a dragger!").

The manipulator maintains consistency between the fields of the dragger and its own fields. Let's say you use the mouse to rotate the dragger. Callbacks insure that the rotation field of the manipulator will change by the same amount, resulting in the rotation of nodes which follow in the scene graph. Similarly, if you set any of the SoTransformManip fields the manipulator will move the dragger accordingly. You can use this feature to impose contraints on a manipulator: If the user moves the manipulator so that a field value becomes too large, you can set the field back to your desired maximum, and the whole thing will move back to where you specified.

Since each SoTransformManip uses a dragger to provide its interface, you will generally be told to look at the dragger's reference page for details of how it moves and what the different parts are for. The interface for the dragger and the manipulator will always be exactly the same. Usually, a SoTransformManip will surround the objects that it influences (i.e., those that move along with it). This is because the manipulator turns on the surroundScale part of its dragger; so the dragger geometry expands to envelope the other objects (see the reference page for SoSurroundScale).

Because the dragger is a hidden child, you can see the dragger on screen and interact with it, but the dragger does not show up when you write the manipulator to file. Also, any SoPath will end at the manipulator. (See the Actions section of this reference page for a complete description of when the dragger is traversed).

If you want to get a pointer to the dragger you can get it from the manipulator using the getDragger() method. You will need to do this if you want to change the geometry of a manipulator, since the geometry actually belongs to the dragger.