[vtkusers] positioning a cylinder

[Mark Wyszomierski]

Hi Amy,

Is there anyway to position vtkArrowSource using just two points?
Something like:

vtkArrow->SetPointHead(x,y,z);
vtkArrow->SetPointTail(x,y,z);

Thanks,
Mark

On 4/2/07, Amy Squillacote <amy.squillacote at kitware.com> wrote:
> Hi Mark,
>
> If what you're wanting is an arrow source class, that already exists in
> VTK. Take a look at vtkArrowSource:
> http://www.vtk.org/doc/release/5.0/html/a01163.html.
>
> - Amy
>
> Mark Wyszomierski wrote:
> > Thanks Amy, and Marc. I will give it a try. My final goal is to have a
> > nice arrow class where I can just do:
> >
> > Arrow->SetHeadPoint(x,y,z);
> > Arrow->SetTailPoint(x,y,z);
> >
> > Doing this with a cone actor is pretty easy (set the origin and
> > direction) but for the shaft(cylinder source) it is more complicated.
> >
> > Thanks,
> > Mark
> >
> > On 3/31/07, Marc Cotran <marc at cotran.ca> wrote:
> >> Hi Mark,
> >>
> >> I have a 'hard' way of doing what you are asking. The easiest way is
> >> what Amy proposes, but if you definitely want a cylinder that can update
> >> quickly with changes to the endpoints...
> >>
> >> - useablePt1 and 2 are classes (Coord) with 3 variables (x, y, z) for
> >> coordinates. Although we implemented some convenience methods in Coord,
> >> you could do it all with vtkMath.
> >>
> >> - this->transform corresponds to that of the actor made from the
> >> cylinderSource
> >>
> >> //////////////////////////////
> >>
> >>    this->cylinderSource = vtkCylinderSource::New();
> >>    this->cylinderSource->SetCapping(1);
> >>    this->cylinderSource->SetResolution(5);
> >>
> >>    // find out halfway point
> >>    Coord halfwayPt(
> >>        (useablePt1.x() + useablePt2.x()) / 2,
> >>        (useablePt1.y() + useablePt2.y()) / 2,
> >>        (useablePt1.z() + useablePt2.z()) / 2);
> >>
> >>    double pos[4];
> >>    double res[4];
> >>
> >>    pos[0] = halfwayPt.x();
> >>    pos[1] = halfwayPt.y();
> >>    pos[2] = halfwayPt.z();
> >>    pos[3] = 1;
> >>
> >>    this->transform.getTransform()->MultiplyPoint(pos, res);
> >>
> >>    // we found the center point
> >>
> >>    Coord diff(this->pt2 - this->pt1);
> >>    Coord normalized(diff.normalize());
> >>
> >>    double norm = diff.norm();
> >>
> >>    this->cachedActor->SetScale(this->radius, norm, this->radius);
> >>
> >>    // get cross product
> >>    double cross[3];
> >>    double input[3];
> >>    double output[3];
> >>
> >>    input[0] = 0;
> >>    input[1] = 1;
> >>    input[2] = 0;
> >>
> >>    output[0] = normalized.x();
> >>    output[1] = normalized.y();
> >>    output[2] = normalized.z();
> >>
> >>    vtkMath::Cross(input, output, cross);
> >>
> >>    // get the angle
> >>    double angle = HelperClass::getAngle(Coord(0,1,0), Coord(),
> >> normalized);
> >>
> >>    // start with no rotation so they don't accumulate
> >>    this->cachedActor->SetOrientation(0,0,0);
> >>
> >>    this->cachedActor->RotateWXYZ(angle, cross[0], cross[1], cross[2]);
> >>
> >>    this->cachedActor->SetPosition(
> >>        res[0] / res[3],
> >>        res[1] / res[3],
> >>        res[2] / res[3]);
> >>
> >> //////////////////////////////
> >>
> >> It is quite possible that the code can be optimized (or at least made
> >> shorter). The only advantage to this method is that you don't have to
> >> remap the actor when you change one or both of the endpoints. If you
> >> don't care about updates, I strongly recommend the lineSource/TubeFilter
> >> method (it's much simpler!!!)
> >>
> >> Marc
> >>
> >>
> >> Mark Wyszomierski wrote:
> >> > Hi,
> >> >
> >> > I have two points in VTK space, is there an easy way to construct a
> >> > cylinder so that its two endpoints touch the two points? Something
> >> > like:
> >> >
> >> > cylinder->SetEndpoint1(x,y,z);
> >> > cylinder->SetEndpoint2(x,y,z);
> >> >
> >> > Thanks,
> >> > Mark
> >> > _______________________________________________
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>
> --
> Amy Squillacote
> Kitware, Inc.
> 28 Corporate Drive
> Clifton Park, NY 12065
> Phone: (518) 371-3971 x106
>
>