[vtkusers] Help with vtkStructuredPoints

[Prabhu Ramachandran]

>>>>> "TJC" == Tan Jui Cheng <(Chen Weizhen)" <jctan at email.com>> writes:

    TJC>         In the "Vol.cxx" example, the dimension is set to
    TJC> 26*26*26, with spacing of 1/25 in x,y,z plane and origin set
    TJC> to (-0.5, -0.5, -0.5). Please correct me if I am wrong, my
    TJC> understanding is that an invisible cubic volume of 26*26*26
    TJC> points having its origin at (-0.5, -0.5, -0.5), the spacing
    TJC> of each point is 1/25 or 0.04. In the example, every point is

Yes, that is correct.  Also remember that the scalars are to be
specified with the x values varying first.  Effectively the reader
reads the data in the following manner:

for z in n_z:
  for y in n_y:
     for x in n_x:
         read_scalar()

The example Vol.cxx makes this clear but when you create a VTK data
file you have to keep this in mind.

    TJC> being defined by the scalar value, s, where s=(x*x+y*y+z*z) -
    TJC> (0.4*0.4), the explicit equation of a sphere. I have tried
    TJC> assigning different value of s, either by assigning it with
    TJC> random numbers or a constant value, but by doing so, nothing
    TJC> will display. Why is this so? So, how can I generate a volume

Because you might be asking for a contour that is not there.  Make
sure your contour filter is asking for the right contour.

      contour->SetValue(0,0.0);
                        ^^^^^^^
                
    TJC> with any scalar value I assign myself? What is the
    TJC> relationship between a scalar value and the "contour-filter"?
    TJC> How can I create a cube instead?

The contour filter simply identifies surfaces which have a consant
scalar value that the user can specify.  Its as simple as that.

prabhu