[vtkusers] Transform a disc from center of earth to surface

[Donny Zimmerman]

I am having trouble figuring out how to transform my 2d disc object to a
point and perpendicular to a vector.

 

I am plotting a weather radar which basically is a bunch of polygons onto a
rendering of the earth (vtkGlobeSource).

 

The world coordinates orgin is the center of the earth. The vector from the
origin to the North Pole is the z axis, the vector from the origin to 0
degrees longitude is up the y axis.

 

I am drawing the radar using local coordinates where the center of the radar
is at (0, 0, 0).

 

I need to translate and rotate the radar plot to the surface of the earth at
a known radar location.

 

The two variables I know are the point on the globe and the vector from the
origin (center of earth) to the radar point. 

 

I have tried to calculate the angle of rotation for each axis but I am not
getting the desired results.

 

Here is a code snippet:

 

//Get World Point Of North Pole      

        vtkGlobeSource::ComputeGlobePoint(0, 90.0,
vtkGeoMath::EarthRadiusMeters(),

            radwp);

        

        double np[3];

        np[0] = radwp[0];

        np[1] = radwp[1];

        np[2] = radwp[2];

        vtkMath::Normalize(np);

 

        //m_wpx, m_wpy, and m_wpz are the radar site coordinates

        double px[3];

        px[0] = m_wpx;

        px[1] = 0;

        px[2] = m_wpz;

        vtkMath::Normalize(px);

 

        double yangle = vtkMath::DegreesFromRadians(acos(vtkMath::Dot(px,
np)));

 

        px[0] = 0;

        px[1] = m_wpy;

        px[2] = m_wpz;

        vtkMath::Normalize(px);

 

        double xangle = vtkMath::DegreesFromRadians(acos(vtkMath::Dot(px,
np)));

 

        //Get World Point Of Equator at 0 Deg Longitude      

        vtkGlobeSource::ComputeGlobePoint(0, 0,
vtkGeoMath::EarthRadiusMeters(),

            radwp);        

 

        double eq[3];

        eq[0] = radwp[0];

        eq[1] = radwp[1];

        eq[2] = radwp[2];

        vtkMath::Normalize(eq);

 

        double pz[3];

        pz[0] = m_wpx;

        pz[1] = m_wpy;

        pz[2] = 0;

        vtkMath::Normalize(pz);

 

        double zangle = vtkMath::DegreesFromRadians(acos(vtkMath::Dot(pz,
eq)));

 

        

        vtkSmartPointer<vtkTransformPolyDataFilter> tf =
vtkSmartPointer<vtkTransformPolyDataFilter>::New(); 

        tf->SetInput(polydata);

        vtkSmartPointer<vtkTransform> xfm =
vtkSmartPointer<vtkTransform>::New();

        xfm->Identity();

        xfm->Translate(m_wpx, m_wpy, m_wpz);        

        xfm->RotateX(xangle);

        xfm->RotateY(yangle);

        // Need to subtract from 180 degrees to point top of radar to north
pole.

        xfm->RotateZ(180.0 - zangle);

        tf->SetTransform(xfm);

 

 

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