Opacity as density for terrain has an invert behavior compare to layer lit shader

Steps to reproduce:

1. Create a terrain
2. Use the red texture joined to create the first terrain layer.
3. Use the blue texture joined to create the second terrain layer.
4. Use the feature "Opacity as Density" for the second/blue layer.
5. Paint the second layer with a low opacity.

Actual results: White parts in the base color alpha appear first.

Expected results: White parts in the base color alpha should appear last.

With a low opacity brush, the painting of the second layer should paint firstly the base color corresponding to the dark area of the alpha channel. More you paint and more the base color pixels appear corersponding to the threshold (alpha channel). At 1 (100%) all the pixels of the second layer are visible.

Reproducible with versions: 6.3

Not reproducible with versions: 

Can’t test with versions: 

Tested on (OS): Windows

Notes:

•