# How to set the center of vtkactor autobiography？
**URL:** https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071
**Category:** Support
**Tags:** proposal
**Created:** [June 25, 2021, 7:34am UTC](https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071 "2021-06-25T07:34:18Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@wulicheng](https://discourse.vtk.org/u/wulicheng)
#### Post date: [June 25, 2021, 7:34am UTC](https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071/1 "2021-06-25T07:34:19Z")
How to set the center of vtkActor autobiography when I moved the translate the actor？
---
### Author:  [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [June 25, 2021, 8:39pm UTC](https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071/2 "2021-06-25T20:39:32Z")
Hello, friend,
Do you mean to set the center of vtkActor automatically when you move (translate) the actor with the mouse?
cheers,
Paulo
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### Author:  [@wulicheng](https://discourse.vtk.org/u/wulicheng)
#### Post date: [June 28, 2021, 12:53am UTC](https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071/3 "2021-06-28T00:53:53Z")
yes! Do you have any suggestions?
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### Author:  [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [June 29, 2021, 12:36pm UTC](https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071/4 "2021-06-29T12:36:28Z")
Hi,
Please, take a look at this example: [https://kitware.github.io/vtk-examples/site/Cxx/Visualization/MoveActor](https://kitware.github.io/vtk-examples/site/Cxx/Visualization/MoveActor) .
take care,
Paulo
---
### Author:  [@wulicheng](https://discourse.vtk.org/u/wulicheng)
#### Post date: [June 30, 2021, 7:52am UTC](https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071/5 "2021-06-30T07:52:54Z")
I have read this code,and run it.But it is not what i want. I want to rotate the actor around a specify 3D point.
And I have tried the SetOrigin() of vtkActor which say:"
/\*\*
- Set/Get the origin of the Prop3D. This is the point about which all
- rotations take place.
\*/
"
the code like this:
virtual void SetOrigin(double x, double y, double z)
{
vtkDebugMacro(\<\< this-\>GetClassName() \<\< " (" \<\< this \<\<
“): setting Origin to (” \<\< x \<\< “,” \<\< y \<\< “,” \<\<
z \<\< “)”);
if ((this-\>Origin[0] != x)||
(this-\>Origin[1] != y)||
(this-\>Origin[2] != z))
{
this-\>Origin[0] = x;
this-\>Origin[1] = y;
this-\>Origin[2] = z;
this-\>Modified();
this-\>IsIdentity = 0;
}
};
But it is not the result! Someone say it must be:
1. Move prop to the origin;
2. Zoom;
3. Rotate around the y-axis;
4. Rotate around the x-axis;
5. Rotate around Z axis;
6. Move back to the original position from the origin;
7. Translation
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### Author:  [@wulicheng](https://discourse.vtk.org/u/wulicheng)
#### Post date: [June 30, 2021, 11:47am UTC](https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071/6 "2021-06-30T11:47:17Z")
Sorry！ I forgot to say it is a stl file.
---
### Author:  [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [July 11, 2021, 12:10pm UTC](https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071/7 "2021-07-11T12:10:12Z")
Hello, friend,
Sorry for the late response. What you’ve been told is somewhat correct since setting its origin is not enough, but it less complicated than that.
The sequence of operations is:
- Translate object to origin;
- Apply rotation;
- Reverse the translation;
Any complex linear transform can be expressed a multiplication of matrices. The sequence of operations is expressed in reverse order:
Y = T-1RT
Where:
Y: the final rotation around a point matrix that you want.
T and T-1: the translation matrix and its inverse.
R: the rotation around the origin matrix.
Then, to rotate your object around a point, simply do X\* = YX, where X is the vector of input coordinates (a matrix with a single column with the x, y, z values) and X\* is the transformed coordinates.
Now to some code. VTK does all that math for you. After setting its center, you can rotate an actor about one of the main axes with `actor->RotateX(45);` for example to rotate about the local X axis by 45º.
If you want to rotate an actor in world coordinates, you can do `actor->RotateWXYZ(45, 1, 0, 0)` to rotate the actor by 45º about the global X axis.
I hope this helps,
Paulo
---
### Author:  [@wulicheng](https://discourse.vtk.org/u/wulicheng)
#### Post date: [July 14, 2021, 11:27am UTC](https://discourse.vtk.org/t/how-to-set-the-center-of-vtkactor-autobiography/6071/8 "2021-07-14T11:27:18Z")
> [@Paulo\_Carvalho](#):
>
> mplex linear transform can be expressed a multiplication of matrices. The sequence of operations is expressed in reverse order:
> Y = T-1RT
> Where:
> Y: the final rotation around a point matrix that you want.
> T and T-1: the translation matrix and its inverse.
> R: the rotation around the origin matrix.
>
> Then, to rotate your object around a point, simply do X\* = YX, where X is the vector of input coordinates (a matrix with a single column with the x, y, z values) and X\* is the transformed coordinates.
>
> Now to some code. VTK does all that math for you. After setting its center, you can rotate an actor about one of the main axes with `actor->RotateX(45);` for example to rotate about the local X axis by 45º.
>
> If you want to rotate an actor in world coordinates, you can do `actor->RotateWXYZ(45, 1, 0, 0)` to rotate the actor by 45º about the global X axis.
>
> I hope this helps,
thank you very much!,it is ok