Re: Access to Cells in VTK.js

point picker or cell picker won't give you the same ijk since one will be
the point ijk vs the cell one.

On Fri, Jan 18, 2019 at 11:42 AM Andrzej Marciniak <
[email protected]> wrote:

> Hi Sebastien,
>
> Thank you for the tip - it works for me. Now, I have only a problem with
> precision in finding IJK.
> Should I better use vtkPicker or vtkMappers to get IJK position of selected
> voxel? I have made a simple experiment with both ways to calculate IJK and
> I
> got different results.
>
>  renderWindow.getInteractor().onRightButtonPress((callData) => {
>             if (renderer !== callData.pokedRenderer) {
>                 return;
>             }
>             const pos = callData.position;
>             const point = [pos.x, pos.y, 0.0];
>             picker.pick(point, renderer);
>             const worldPos = picker.getPickedPositions()[0];
> //I have only one Actor in renderer but 3 mappers set on different planes
>             let slices = null;
>             try {
>                 slices = mappers.map((el) => {
>                     return el.getSliceAtPosition(worldPos) // this is how I
> get I,J,K with ImageMapper API
>                 });
>             }
>             catch (err) {  alert("You cannot pick a point outside MRI
> volume");
>                 return;
>             }
>             const pointIndex = slices[0] + slices[1] * dims[0] + slices[2]
> *
> dims[0] * dims[1];
>             const pointIndex2 = picker.getCellIJK()[0]
>                                + picker.getCellIJK()[1] * dims[0]
>                                + picker.getCellIJK()[2] * dims[0] *
> dims[1];
>             if (pointIndex===pointIndex2)
> inputData.getPointData().getScalars().getData()[pointIndex]=1983;
>
>             else {
>
> inputData.getPointData().getScalars().getData()[pointIndex]=1700;
>
> inputData.getPointData().getScalars().getData()[pointIndex2]
> = 1500;
>             }
>         });
> <http://vtk.1045678.n5.nabble.com/file/t342677/pickerProblem.png>
> As a result I have different voxels marked (please see image).  White voxel
> is when they agree, light- and dark-grey when they don't. The results are
> different when the selected point on canvas is close to the border of voxel
> (points 1 and 3).
> Which way is better?  Can be direction of the vtkDataImage problem here
> (its
> not aligned with xyz coordinates)?
> Thank you again
> Andrzej
>
>
>
> --
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