# Cannot call SetScalar()
**URL:** https://discourse.vtk.org/t/cannot-call-setscalar/14419
**Category:** Support
**Tags:** code
**Created:** [August 15, 2024, 5:04am UTC](https://discourse.vtk.org/t/cannot-call-setscalar/14419 "2024-08-15T05:04:43Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Taco\_Z](https://discourse.vtk.org/u/Taco_Z)
#### Post date: [August 15, 2024, 5:04am UTC](https://discourse.vtk.org/t/cannot-call-setscalar/14419/1 "2024-08-15T05:04:43Z")
I’m new to VTK and I try to use VTK9.1 + QT6 to display points cloud.
I found tutorials and examples for displaying points cloud with different color by calling SetScalar().
Here’s the code:
vtkSmartPointer points = vtkSmartPointer::New();
vtkSmartPointer colors = vtkSmartPointer::New();
colors-\>SetNumberOfComponents(3); // RGB
colors-\>SetName(“Colors”);
//Here’s code to read points cloud
points-\>InsertNextPoint(x,y,z);
//here’s code for color
…
unsigned char color[3] = {r, g, b};
colors-\>InsertNextTypedTuple(color);
//
// display
vtkSmartPointer polyData = vtkSmartPointer::New();
polyData-\>SetPoints(points);
// basically this is the typical way to add colors to points, but I cannot call SetScalars(colors) after “polyData-\>GetPointData()”. I don’t know how to fix this.
polyData-\>GetPointData()-\>SetScalars(colors);
can anyone help me ? I want a colorful points cloud model in the window.
---
### Author:  [@rexthor](https://discourse.vtk.org/u/rexthor)
#### Post date: [August 15, 2024, 12:25pm UTC](https://discourse.vtk.org/t/cannot-call-setscalar/14419/2 "2024-08-15T12:25:47Z")
I don’t do much VTK C++, but from [the documentation](https://vtk.org/doc/nightly/html/classvtkDataSetAttributes.html#a426009e9d6ac5a4b2cda670aed78042d), SetScalars requires a vtkDataArray, have you converted `colors` to a vtkDataArray?
---
### Author:  [@Taco\_Z](https://discourse.vtk.org/u/Taco_Z)
#### Post date: [August 20, 2024, 5:09am UTC](https://discourse.vtk.org/t/cannot-call-setscalar/14419/3 "2024-08-20T05:09:58Z")
yes, I found it should be declared by this type rather than use smartpointer
rexthor via VTK \<[noreply@discourse.vtk.org](mailto:noreply@discourse.vtk.org)\> 于2024年8月15日周四 20:25写道：