# Logic behind "Warp By Vector" Reset Scalar Factor button
**URL:** https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482
**Category:** ParaView Support
**Tags:** vtk
**Created:** [February 24, 2023, 6:34am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482 "2023-02-24T06:34:33Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@Albers\_Steven](https://discourse.paraview.org/u/Albers_Steven)
#### Post date: [February 24, 2023, 6:34am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482/1 "2023-02-24T06:34:33Z")
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!
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 24, 2023, 8:47am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482/2 "2023-02-24T08:47:25Z")
Hi @Albers_Steven
It’s handled by the vtkSMBoundsDomain, in array scaled extent mode.
```auto
Each component of the selected vector array will be
multiplied by the value of this property before being used to compute
new point coordinates.
```
The doc is here:
[https://kitware.github.io/paraview-docs/latest/cxx/classvtkSMBoundsDomain.html#ab291fcc0b9345a01a36337b34d4a8dd0ae46aa9978e10f02a8d3e06194d77085f](https://kitware.github.io/paraview-docs/latest/cxx/classvtkSMBoundsDomain.html#ab291fcc0b9345a01a36337b34d4a8dd0ae46aa9978e10f02a8d3e06194d77085f)
hth,
---
### Author:  [@Albers\_Steven](https://discourse.paraview.org/u/Albers_Steven)
#### Post date: [February 24, 2023, 10:43am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482/3 "2023-02-24T10:43:25Z")
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
```auto
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.
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 24, 2023, 10:47am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482/4 "2023-02-24T10:47:51Z")
Ok, is there a bug ? This is not clear.
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### Author:  [@Albers\_Steven](https://discourse.paraview.org/u/Albers_Steven)
#### Post date: [February 25, 2023, 2:54am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482/5 "2023-02-25T02:54:29Z")
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?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 27, 2023, 8:29am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482/6 "2023-02-27T08:29:58Z")
What is the behavior you expect ? In which context ?
What is the behavior you get ?
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### Author:  [@Albers\_Steven](https://discourse.paraview.org/u/Albers_Steven)
#### Post date: [February 27, 2023, 10:41am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482/7 "2023-02-27T10:41:31Z")
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`
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 27, 2023, 10:42am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482/8 "2023-02-27T10:42:29Z")
So I’m asking once again, is ParaView behavior expected ? If yes, what is your actual question ?
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### Author:  [@Albers\_Steven](https://discourse.paraview.org/u/Albers_Steven)
#### Post date: [February 28, 2023, 3:53am UTC](https://discourse.paraview.org/t/logic-behind-warp-by-vector-reset-scalar-factor-button/11482/9 "2023-02-28T03:53:00Z")
Yes, Paraview behaviors as expected, sorry to bother you.