[vtkusers] Changes in diffuse properties of material.

[Seun Odutola]

Hi everyone,

    I recently discovered whilst working with VTK master that some meshes are completely rendered dark in colour compared to others; meshes that rely on their material (actor’s properties) are mostly affected. I tracked the occurrence of this change down to the following commit below and was wondering the essence of the change, also if need be how can one replicate the previous rendering behaviour.

- commit 7bc7e58334bcd1eac12adb6db22d6c45cf8fca74
Author: Ken Martin <ken.martin at kitware.com>
Date:   Thu Aug 31 13:08:58 2017 -0400

    update handling of scalar material mode
    
    Previously scalar material mode when used
    with scalars would ignore the ambient and diffuse
    material intensities and when mapping one of them
    set that one to 1.0 while leaving th eother alone.
    This caused lots of odd situations where objects would be
    over illuminated etc or where changing the diffuse or
    ambient seemed to have o impact.
    
    With this change the diffuse and ambient intensities
    are always used. The sclaar simply controls the color
    not the intensity. 


Thanks.

Regards,
   Seun.