# why vtkResliceCursor set a negative in vtkResliceCursor.cxx file?

**URL:** https://discourse.vtk.org/t/why-vtkreslicecursor-set-a-negative-in-vtkreslicecursor-cxx-file/1800
**Category:** Support
**Created:** [September 23, 2019, 7:36am UTC](https://discourse.vtk.org/t/why-vtkreslicecursor-set-a-negative-in-vtkreslicecursor-cxx-file/1800 "2019-09-23T07:36:31Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![pingdan](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/p/22d042/32.png) [@pingdan](https://discourse.vtk.org/u/pingdan)
#### Post date: [September 23, 2019, 7:36am UTC](https://discourse.vtk.org/t/why-vtkreslicecursor-set-a-negative-in-vtkreslicecursor-cxx-file/1800/1 "2019-09-23T07:36:31Z")

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when I search the file ‘vtkResliceCursor.cxx’ and find as below:  
vtkResliceCursor::vtkResliceCursor()  
{  
…  
…  
this-\>ReslicePlanes-\>GetItem(0)-\>SetNormal(1,0,0);  
this-\>ReslicePlanes-\>GetItem(1)-\>SetNormal(0,-1,0);  
this-\>ReslicePlanes-\>GetItem(2)-\>SetNormal(0,0,1);  
…  
}  
from this function , the x and z axis have set the positive value, why y axis set a negative value? does that mean something special use?