Manipulators and Draggers
The strong points of Open Inventor are the ease of creating 3D user
interfaces. Manipulators and Draggers are objects for user
interaction like a scrollbar or button in a 2D user interface.
A Dragger use user input via the mouse to visualize the change and to
provide the change for other objects in the scene graph. This has to be
programmed explicitly compared to a Manipulator. A Manipulator is
in principle a dragger plus an object (e.g., Transform Node) which is part of a scene graph.
Dragger
The output of a dragger needs to be given to the scene graph via
connections (and might pass some engines) or via a callback function which is
controlled by the application.
| Display | Graph |
|
|
In our example we connect a SoScale node with SoScale1Dragger.
Constrained Dragger
A dragger can be constrained by a callback function
(e.g. addChangeValueCB) or an engine.
| Display | Graph |
|
|
In our example we plug between
the dragger and the scaling node a calculator which constrains the
size in x direction. The expression for the calculator is:
oA= (A[0]<1.2) ? A : vec3f(1.2,A[1],A[2])
Manipulator
A Manipulator is an interactive version of a node
(transformation, light, ..). This will be more clear by looking at the
class hierarchy. So is for example SoTransformManip a sub class of SoTransform.
| Display | Graph |
 |  |
The Manipulator example shows the
SoTransformerManip node, which allows to change size, transformation
and rotation.
Constrained Manipulator
A Manipulator can be easily constrained by attaching a callback function
to the connected Dragger.
The Manipulator is
constrained in size by using following callback function:
void valueChangedCB(void *user, SoDragger *inDragger)
{
// we need access to the fields
SoTransformerDragger *dragger = (SoTransformerDragger *) inDragger;
// constrain in X direction
if (dragger->scaleFactor.getValue()[0] > MAXSIZE)
dragger->scaleFactor.setValue(MAXSIZE,
dragger->scaleFactor.getValue()[1],
dragger->scaleFactor.getValue()[2]);
else
if (dragger->scaleFactor.getValue()[0] < MINSIZE)
dragger->scaleFactor.setValue(MINSIZE,
dragger->scaleFactor.getValue()[1],
dragger->scaleFactor.getValue()[2]);
}
The executable is also available (compiled with OI 2.1.1, so you need
the latest run-time libraries).
Jens Herder