### Description

Demonstrates the gradient backgrounds available in VTK.

The gradient background modes are:

- Vertical
- Horizontal
- Radial Farthest Side
- Radial Farthest Corner

The user can also edit the code to change the stop colors marking the beginning and end points in a gradient.

An option is provided for the user to read in a data file so that more interesting objects can be viewed.

The viewport border can also be set and colored.

For more information, see [New in VTK 9.3: Radial Gradient Background](https://www.kitware.com/new-in-vtk-9-3-radial-gradient-background/)

!!! note VTK 9.3 or later is required.

!!! note The C++ version requires C++ 17 or later as std::filesystem is used.
