[vtkusers] Picking invisible object !

[Sebastien Auclair]

Greetings,

I need to allow the user to drag a picked object but not in X, Y direction
on the display plane.
For instance, he must be able to drag a cube on the World X axis only.
To do that, my approach so far is to create an invisible vtkPlane that i try
to use to compute an intersection point with a ray i create based on
DisplayToWorld and the mouse coordinates.

Maybe because we are in parallel display mode, the results so far are not
correct.When the display plane fits the vtkPlane, the object follows the
mouse.
But as the vtkPlane's normal becomes closer to be perpendicular to the
project vector, the objects can't move enough to keep up with the mouse
cursor.

I used, among other things, the functions vtkPlane::GeneralizedProjectPoint
and\or vtkPlane::ProjectPoint but they are not really documented so i can't
tell what the problem is.

I though of really picking the plane to query the picking point but the
vtkPlane cannot be displayed of course.
Is there a way to pick something like implicit function class.

Any suggestion folks ?


Thanks !
____________________________________
Seb