[vtkusers] Problem with vtkActor->SetOrigin()
王君臣
wangjunchen at gmail.com
Wed May 26 07:17:07 EDT 2010
it seems strange...
if you only set the origin by SetOrigin and keep others 0 or identity, it
should take no effect...
please notice the setposition, in your test, is it (0, 0, 0) ?
if everything is paid enough attention, could you please post your code
snippet?
2010/5/26 Anant Vemuri <ajar108 at gmail.com>
> 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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>>>> >>
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>>>> >>
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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
>>>
>>> Follow this link to subscribe/unsubscribe:
>>> http://www.vtk.org/mailman/listinfo/vtkusers
>>>
>>>
>>
>>
>> --
>>
>>
>
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