[vtkusers] Problem with vtkActor->SetOrigin()
Anant Vemuri
ajar108 at gmail.com
Wed May 26 06:39:21 EDT 2010
Thank you Wang. I went through the file and also the documentation. Here are
the steps I did to test,
1. I applied nothing, no SetOrigin(), no SetUserTransform() and put my
object in the scene. - image name = nothing_applied.jpg
2. The I apply SetOrigin(-0.443477, -0.285047, 10.1173), and no
SetUserTransform() this gives me result shown in image =
setOrigin_applied.jpg
>From what I read in your email and the documentation, this should not
happen, right? Or am I interpreting it wrong. If not, then this is what is
baffling me.
Best regards,
Anant.
-----------
Anant S. Vemuri
email: ajar108 at gmail.com
2010/5/26 王君臣 <wangjunchen at gmail.com>
>
> Hi, sorry for my uncompleted explanation. Now let's study the
> underlying mechanism of "SetOrigin etc." together.
> here is the source code of vtkProp3D::ComputeMatrix (vtk 5.4)
>
> void vtkProp3D::ComputeMatrix()
> {
> if (this->IsIdentity)
> {
> return;
> }
> // check whether or not need to rebuild the matrix
> if ( this->GetMTime() > this->MatrixMTime )
> {
> this->GetOrientation();
> this->Transform->Push();
> this->Transform->Identity();
> this->Transform->PostMultiply();
> //* Notice This Code segment*
> // begin {
> // shift back to actor's origin
> this->Transform->Translate(-this->Origin[0],
> -this->Origin[1],
> -this->Origin[2]);
> // scale
> this->Transform->Scale(this->Scale[0],
> this->Scale[1],
> this->Scale[2]);
> // rotate
> this->Transform->RotateY(this->Orientation[1]);
> this->Transform->RotateX(this->Orientation[0]);
> this->Transform->RotateZ(this->Orientation[2]);
> // move back from origin and translate
> this->Transform->Translate(this->Origin[0] + this->Position[0],
> this->Origin[1] + this->Position[1],
> this->Origin[2] + this->Position[2]);
> //}end ==> it means: at first, the actor frame is an identity (same
> with the world frame), then you have a chance to rotate or/and scale the
> identity frame with respect to a point (specified by setorigin) in the world
> frame. after that, the usermatrix takes efforts.
> // apply user defined transform last if there is one
> if (this->UserTransform)
> {
> this->Transform->Concatenate(this->UserTransform->GetMatrix());
> }
> this->Transform->PreMultiply();
> this->Transform->GetMatrix(this->Matrix);
> this->MatrixMTime.Modified();
> this->Transform->Pop();
> }
> }
> 2010/5/26 Anant Vemuri <ajar108 at gmail.com>
>
> Hi,
>>
>> I had posted a problem a few days back that I am still having with using
>> vtkActor->SetOrigin(). The documentation of vtkProp3D says that
>> SetOrigin(pos) function sets the point of rotation to the point specified by
>> pos. However, when I apply SetOrigin(pos), my actor moves in the scene such
>> that his point is at the world origin. For example, if I do SetOrigin(100,
>> 100, 100), the actor moves such that the previous (100,100,100) is now at
>> (0,0,0) initially before I apply any other transform to it. The effect is
>> similar to when I do
>>
>> m_transform->Translate( -100,-100,-100 );
>> m_actor->SetUserTransform( m_transform );
>>
>>
>> Is this what is expected? Becase from the documentation, I understood that
>> it should do translate(-newOrigin) [rotations, scaling etc]
>> translate(newOrigin). Should I expect that when I do
>> vtkActor->SetOrigin(newOrigin), the newOrigin moves to the world (0,0,0).
>> Can someone explain this to me?
>>
>> Thank you.
>> Anant.
>>
>>
>> On Mon, May 24, 2010 at 11:27 PM, Anant Vemuri <ajar108 at gmail.com> wrote:
>>
>>> Thanks... But doesn't SetUserTransform() do that already... the vtk
>>> documentation says as below...
>>>
>>> I think I understand the problem, but not sure how to correct it... I
>>> am attaching a transform as the base transform which means that all
>>> the other operations such as SetOrigin(), SetScale() get overridden.
>>>
>>>
>>> On 5/24/10, 王君臣 <wangjunchen at gmail.com> wrote:
>>> > what you need is a multiplication (PostMultiply) of m_defaultTrf to the
>>> > current actor transform not a replacement.
>>> >
>>> >
>>> > 2010/5/24 Anant Vemuri <ajar108 at gmail.com>
>>> >
>>> >> Hi,
>>> >>
>>> >> I am trying to use myVtkActor->SetOrigin(origin) to set the origin so
>>> that
>>> >> any rotations I apply is done about this point. This is what I do to
>>> build
>>> >> the pipeline
>>> >>
>>> >>
>>> >> void buildPipeline( )
>>> >> {
>>> >> m_actor->SetMapper( m_mapper );
>>> >> m_actor->SetOrigin( 100, 100, 100 );
>>> >> m_defaultTrf->Scale(m_scale, m_scale, m_scale);
>>> >> m_defaultTrf->PostMultiply();
>>> >> m_defaultTrf->Concatenate( this->getTransform() );
>>> >> /// I add some more things to the m_defaultTrf
>>> >> .
>>> >> .
>>> >> .
>>> >> m_actor->SetUserTransform( m_defaultTrf );
>>> >> }
>>> >> std::cout << "\n\n\nOrigin = [" << m_actor->GetOrigin()[0] << ", "
>>> <<
>>> >> m_actor->GetOrigin()[1] << ", " << m_actor->GetOrigin()[2] <<
>>> "]\n\n\n";
>>> >> }
>>> >>
>>> >> But when I apply the transform in the scene, it is not being about
>>> some
>>> >> other point entirely. I noticed that this is the same point when I
>>> remove
>>> >> the SetOrigin() line. But in the last line it gives me the origin as
>>> the
>>> >> one
>>> >> that I set a few line earlier. I am not able to figure out what is the
>>> >> mistake. Can anyone help me?
>>> >>
>>> >> Thank you.
>>> >> Anant.
>>> >>
>>> >> _______________________________________________
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>>> >>
>>> >
>>> >
>>> > --
>>> >
>>>
>>>
>>> --
>>> -----------
>>> Anant S. Vemuri
>>> email: ajar108 at gmail.com
>>>
>>
>>
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Please keep messages on-topic and check the VTK FAQ at:
>> http://www.vtk.org/Wiki/VTK_FAQ
>>
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>>
>>
>
>
> --
>
>
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