[vtkusers] Re: Using vtkCutter on a transformed model

[Goodwin Lawlor]

Clare Fitzpatrick wrote:
> Hi, I am trying to orientate a 3D model so that a particular vector is 
> aligned with the z-axis in world coordinates.
> I have tried:
>  
> vtkSTLReader model
>         model SetFileName "C:/myFile"
> ...
> I am applying an instance of vtkCutter to this model.
>  
> vtkCutter cutter1
> cutter1 SetInput [model GetOutput]
> ...
> then when I transform the model using
>  
>         modelActor RotateWXYZ angle1 0 0 1
>         modelActor RotateWXYZ angle2 0 1 0
>  
> the model is transforming correctly but cutter1 is not cutting the model 
> anymore.
>  
> When I use a transform:
> vtkTransform modelTransform
>    
> vtkTransformPolyDataFilter modTransform
>     modTransform SetTransform modelTransform
>     modTransform SetInput [model GetOutput]
>  
> and then
> cutter1 SetInput [modelTransform GetOutput]
> ...
> and then transform the model using
>         modelTransform RotateWXYZ angle1 0 0 1
>         modelTransform RotateWXYZ angle2 0 1 0
>  
> its producing the wrong output - i think it might be using the model 
> coordinates instead of the world ones.
>  
> Any ideas on how to set the cutter to work on the (correctly) 
> transformed model??
>  
> Clare
> 

Hi Clare,

vtkProp3D::RotateWXYZ uses a PostMultiply transform whereas 
vtkTransform::RotateWZYZ uses PreMultiply by default. Try:

modTransform PostMultiply

and you should get the same output.

Here's a trick to get the the output of the cutter to keep up with an 
actors transform: use vtkImplicitFunction::SetTransform and 
vtkProp3D::SetUserTransform to share a common vtkTransform.

So...


vtkSTLReader model
    model SetFileName filename.stl

vtkTransform actorTranform

vtkPlane cutterPlane
    cutterPlane SetTransform actorTransform

vtkCutter cutter
    cutter SetCutFunction cutterPlane
    cutter SetInput [model GetOutput]

vtkPolyDataMapper cutterMapper
    cutterMapper SetInput [cutter GetOutput]

vtkActor cutterActor
     cutterActor SetMapper cutterMapper

vtkPolyDataMapper mapper
    mapper SetInput [model GetOutput]

vtkActor actor
    actor SetMapper mapper
    actor SetUserTransform actorTransform

actorTransform PostMultiply
actorTranform RotateWXYZ 30 0 0 1

hth

Goodwin