Change default light softness from 0 to 0.2.

PiperOrigin-RevId: 960218397
Change-Id: I58f211f5a275f8f19254424facd02c14eaa8c668

doc/XMLreference.rst

@@ -3323,7 +3323,7 @@ Attributes may be applied or ignored depending on the lighting model being used.
 
 .. _body-light-softness:
 
-:at:`softness`: :at-val:`real, "0"`
+:at:`softness`: :at-val:`real, "0.2"`
    Edge softness for spotlights, as a fraction of the :ref:`cutoff<body-light-cutoff>` angle in [0, 1], used by
    physically-based lighting models. The light delivers its full :ref:`intensity<body-light-intensity>` inside the
    cone, falling to zero over the outer softness fraction of the cone angle; the default corresponds to a sharp-edged

doc/changelog.rst

@@ -75,7 +75,7 @@ Rendering
    :class: attention
 
    - Added :ref:`light/softness<body-light-softness>`: edge softness for spotlights under physically-based lighting
-     models, given as the fraction of the cone over which intensity falls to zero. The default of 0 is a sharp-edged
+     models, given as the fraction of the cone over which intensity falls to zero. The default of 0.2 is a semi-soft
      cone which delivers the full :ref:`intensity<body-light-intensity>` everywhere inside it, so that illuminance
      follows :math:`E = I/d^2` independent of the :ref:`cutoff<body-light-cutoff>` angle. Previously the filament
      renderer treated the entire cone as penumbra, dimming spotlights well below their rated intensity, increasingly