[vtkusers] Picking points from multiple surfaces.

[安 继业]

Hi.

I extract multiple isosurfaces from a data set by vtkContourFilter, just as 
the vtk examples Medical/Medical2.cxx illustrated. Now I want to pick 
points from the displayed surfaces. Here's some questions:

1. Generally, a keypress "P" is used to perform a picking operation. This 
is somewhat inconvenient for users. So I want to picking points by press 
the left mouse button. When the left button is pressed, I want to get the 
world coordinates at that point. How to achieve this?

2. Since there are multiple surfaces displayed in the same render window 
together, how can I determin which surface the picking point is on? And can 
I pick points on each surface by mouse?

3. If I extract 2 surfaces from one data set, and 2 surfaces from another 
dataset, can I display them together? Simply by add the 4 separate actors 
to the rendering window? Are the latter 2 isosurfaces of the same 
coordinate system with the former 2? For example, if I pick a point from 
one surface from the surface of the first data set and get it's coordinate 
(1, 1, 1), and another point from the surface of the second dataset with 
coordinate (2, 2, 2), so can these two coordinates be compared to calculate 
the shift between the two data sets?

Any suggestion will be appreciated. Thank you in advance.

Jiye An

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