[vtkusers] Changing the direction of Z

[Jim Peterson]

Paul Harris wrote:
>
>
> On 19 October 2010 06:31, Jim Peterson <jimcp at cox.net 
> <mailto:jimcp at cox.net>> wrote:
>
>     Paul Harris wrote:
>
>
>         My models do not have any particular handedness, ...
>
>     all 3D models have a "handedness" Right handed says the  positive
>     Y axis is a 90degree rotation counter clockwise from the positive
>     X axis, the positive Z axis is 90 degrees counter clockwise from
>     the  X/Y plane along the  Y positive axis. "Left handed" is the
>     same rule with "counter clockwise" replaced with "clockwise". you
>     trasnform between the two by either reversing the direction of Z
>     or exchanging X and Y.
>
>
> Ok well in that case, some of the models I view are right-handed, some 
> are left-handed.  I need to support both.
> I might have no choice but to insist on whatever VTK is happy with.
Paul,
the essential problem here is the input polydata (at whatever point that 
exists is the manifestation in the current world coordinate system of 
the objects represented by the numbers generated by the original 
coordinate system. The vtkPolyDataFilter is designed to adjust all model 
related aspects of the poly data, it needs to be applied to the poly 
data, not the actor. My reasoning is multiple input objects, some right 
handed, some left handed, may be processed as inputs to the same mapper 
or actor. So in my Java reinterpretation of your program, the dark  
surface problem is resolved by applying the vtkPolydata filter to the 
output of the cone source, and using the output of the filter in the 
mapper.... as:

       ....
           vtkTransformPolyDataFilter xffilt = new 
vtkTransformPolyDataFilter();
           vtkTransform xform = new vtkTransform();
           xform.Identity();
           xform.Translate(2,0,0);
           xform.Scale(-1,1,-1);
          
           xffilt.SetInput(conef.GetOutput());
           xffilt.SetTransform(xform);
          
           coneMapperf.SetInput(xffilt.GetOutput());
          ....

I also made sure the black object was visible by setting the renderer 
background to a tasteful blue....

           ren.SetBackground(0.1, 0.2, 0.4);

I believe we would have to class this issue as incorrect pipeline usage, 
not a bug.

HTH,
Jim