### Description
This example demonstrates the generation of normals. The left image
shows the orignal faceted model. The center image shows the model with
generated normals, but no consideration for sharp features. The third
image shows the model with a 30 degree feature angle and splitting
on.

Theis example uses the [42400-IDGH.stl](https://github.com/lorensen/VTKExamples/raw/master/src/Testing/Data/42400-IDGH.stl) dataset.

!!! note
    This example is a modification of Figure 9-24 in the [VTK Text Book](https://www.kitware.com/products/books/VTKTextbook.pdf).

