Logic behind "Warp By Vector" Reset Scalar Factor button

Hi, I’m using a file to use this “Warp By Vector” filter function.

When a click this filter, it give me a default scalar factor value of number 1. But when I click reset button, it picked a reasonable value for me, but i don’t really know what Paraview did behind this action.

So, Could you show me the algorithm about this reset action?

I’ve checked code of Paraview git repo, but I can’t find this code.

Please help me!

Hi @Albers_Steven

It’s handled by the vtkSMBoundsDomain, in array scaled extent mode.

      <DoubleVectorProperty command="SetScaleFactor"
        <BoundsDomain name="range" mode="array_scaled_extent">
            <Property function="Input" name="Input" />
            <Property function="ArraySelection" name="SelectInputVectors" />
        <Documentation>Each component of the selected vector array will be
        multiplied by the value of this property before being used to compute
        new point coordinates.</Documentation>

The doc is here:


1 Like

Cool. For my case, to use Warp by vector scalar factor. I run into this code to calculate the maxBounds value.

Then I look into .h file, explain that for

ARRAY_SCALED_EXTENT: the range is set to (0, (arrayMagnitude / maxbounds) * this->ScaleFactor)
where maxbounds is the length of the longest axis for the bounding box. and arrayMagnitude the maximum magnitude of the array.

But in all case, the default scalarFactor value is set to 0.1.

So, when I use this formula (arrayMagnitude / maxbounds) * this->ScaleFactor) this->ScaleFactor value is always 0.1. And finally, the results is not equal to paraview app value.

Ok, is there a bug ? This is not clear.

No, I mean according that code, I can only get maxbounds value, and this->ScaleFactor value is always default 0.1, so at last the results is not equal to Paraview app results. So I wonder if I miss something?

What is the behavior you expect ? In which context ?

What is the behavior you get ?

First, Sorry for my description before. I’m using vtk.js to use warp by vector filter.

For example, a density.vtk

It’s bounds are [0, 16.51, -5.66214, 5.66214, 23.3312, 36.195] and the vector Momentum dataRange is [-368.5409851074219, 368.37799072265625], [-392.2900085449219, 380.30999755859375], [-287.2699890136719, 297.85101318359375],

In this function above, i think
this->ArrayRangeDomain->GetNumberOfEntries() = 3,
and then arrayScaleFactor is 349.1066640218099 after line 300;

At line 302, maxbounds is 16.51. So in line 303 maxbounds equals
(0.1 / 349.1066640218099) * 16.51 = 0.004729213647714433.

Thus, the max value of scalar factor should be this value 0.004729213647714433.

But when i use paraview to warpbyvector, and paraview give me the max value of scalar factor is 0.00519717. and it’s not equal. 0.00519717 != 0.004729213647714433

So I’m asking once again, is ParaView behavior expected ? If yes, what is your actual question ?

Yes, Paraview behaviors as expected, sorry to bother you.