[vtkusers] Changing the direction of Z

[Bill Lorensen]

Yes, user matrix should work. But a negative scale will mess up the
shading calculation. The user matrix is used by opengl. Not sure why
reverse sense did not work.

Try the same thing (as an experiment) with vtkTransformPolyData.

On Sat, Oct 16, 2010 at 7:46 PM, Paul Harris <harris.pc at gmail.com> wrote:
> On 16 October 2010 21:25, Bill Lorensen <bill.lorensen at gmail.com> wrote:
>>
>> You can use the vtkTransformPolyDataFilter
>>
>
> That will make a copy of the points and then adjust all the values, right?
>
> There is quite a lot of points to plot, I was hoping to use an approach that
> wouldn't involve using more memory.
>
> Earlier, I tried this approach:
> vtkTransform * flipform = vtkTransform::New();
> flipform->Identity();
> flipform->Scale(1,1,-1);
> actor_flip->SetUserMatrix( flipform->GetMatrix() );
>
> And that worked find *except* that all of the surfaces look dark, as if they
> are facing away from the camera.
>
> I looked around and tried adding vtkReverseSense to the chain, but that
> didn't make any difference at all.
>
> Should I be able to use SetUserMatrix?
>
>
>
>>
>> On Sat, Oct 16, 2010 at 9:06 AM, Paul Harris <harris.pc at gmail.com> wrote:
>> > The models themselves.   Flipping the ViewUp seems to be the same as
>> > turning
>> > the monitor upside down, but that is not the result I want.
>> > The problem is that Z in model coordinates is "downwards", but vtk seems
>> > to
>> > insist that Z is "upwards".
>> > This problem is not just for Z either,
>> > I also have the situation where in some circumstances, the Y should
>> > point
>> > the other way.   ie, Y means South rather than North.
>> >
>> >
>> > On 16 October 2010 03:32, Bill Lorensen <bill.lorensen at gmail.com> wrote:
>> >>
>> >> Do you want the models flipped, or just the view of the models?
>> >>
>> >> If it is the latter, you can set the ViewUp of the camera to 0,0,-1.
>> >>
>> >>
>> >> On Fri, Oct 15, 2010 at 3:17 PM, Paul Harris <harris.pc at gmail.com>
>> >> wrote:
>> >> > Hi all,
>> >> >
>> >> > I have a VTK scene with some vtkPolyDataMappers and actors, plus an
>> >> > orientation widget.
>> >> >
>> >> > I want to change the fundamental direction of the Z axis, so that it
>> >> > points
>> >> > down rather than up.  I want all of the models, the orientation
>> >> > widget,
>> >> > etc
>> >> > to flip, so that they point down instead of up.
>> >> >
>> >> > I've tried lots of things but have gotten nowhere...
>> >> >
>> >> > how do I make this happen?
>> >> >
>> >> > thanks
>> >> > Paul
>> >> >
>> >> >
>> >> >
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