# [vtkusers] reslice using an arbitrary orientation

zandarina esmeralda.ruiz at alma3d.com
Mon Mar 25 15:08:19 EDT 2019

```Dear all

I want to reslice a 3d volume computing the perpendicular
between two points x and y. I compute the
perpendicular berween point 1, point2 in x and y (z is the same for all
points as the
poins are obtained of one slice)

And then i compute the perpendicular of x and y
And i compute the rotation. And i get a blank image. I would like to
cut the slice cutting through the perpendicular of those two points.

I attach the code. Is there something wrong

Any help?

double vt[3];
vt[0] = pts2[0] - pts1[0];
vt[1] = pts2[1] - pts1[1];
vt[2] = pts2[2] - pts1[2]; // it will be 0 as z is the same in all
points
double perpendicular[3] = { -vt[1],vt[0],0 };

double startPoint[3], endPoint[3];
startPoint[0] = tar_cen[0];
startPoint[1] = tar_cen[1];
startPoint[2] = tar_cen[2];
endPoint[0] = startPoint[0] + perpendicular[0];
endPoint[1] = startPoint[1] + perpendicular[1];
endPoint[2] = startPoint[2] + perpendicular[2];

// Compute a basis
double normalizedX[3];
double normalizedY[3];
double normalizedZ[3];

// The X axis is a vector from start to end
vtkMath::Subtract(endPoint, startPoint, normalizedX);
//double length = vtkMath::Norm(normalizedX);
vtkMath::Normalize(normalizedX);

// The Z axis is an arbitrary vector cross X
double arbitrary[3];
arbitrary[0] = vtkMath::Random(-10, 10);
arbitrary[1] = vtkMath::Random(-10, 10);
arbitrary[2] = vtkMath::Random(-10, 10);
vtkMath::Cross(normalizedX, arbitrary, normalizedZ);
vtkMath::Normalize(normalizedZ);

// The Y axis is Z cross X
vtkMath::Cross(normalizedZ, normalizedX, normalizedY);
vtkSmartPointer<vtkMatrix4x4> matrix =
vtkSmartPointer<vtkMatrix4x4>::New();

// Create the direction cosine matrix
matrix->Identity();
for (unsigned int i = 0; i < 3; i++)
{
matrix->SetElement(i, 0, normalizedX[i]);
matrix->SetElement(i, 1, normalizedY[i]);
matrix->SetElement(i, 2, normalizedZ[i]);
}

// Apply the transforms
vtkSmartPointer<vtkTransform> transform =
vtkSmartPointer<vtkTransform>::New();
transform->Translate(startPoint);
transform->Concatenate(matrix);

reslice->SetResliceTransform(transform);

//Step 3: done
reslice->Update();

--
Sent from: http://vtk.1045678.n5.nabble.com/VTK-Users-f1224199.html
```