Add Filament lighting and shadow features and fixes.

- Add a hidden directional light to Filament scenes with no lights to work around soft shadow blackout bug.
- Respect quality/shadowsize as default shadow map resolution.
- Interpret light/bulbradius in correct units for each shadow type and update XML reference docs.
- Support updating the shadow map resolution of live Filament lights.
- Clamp light intensities to non-negative values in the Filament debug panel.

PiperOrigin-RevId: 957305808
Change-Id: Ic7a3430aaa3b117be7fbb7ace836d68e54cdf65a

doc/APIreference/functions.rst

@@ -3429,6 +3429,15 @@ Enables or disables the light.
 
 Sets the intensity of the light, in candela.
 
+.. _mjrf_setLightShadowMapSize:
+
+`mjrf_setLightShadowMapSize <#mjrf_setLightShadowMapSize>`__
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. mujoco-include:: mjrf_setLightShadowMapSize
+
+Sets the resolution of the light's shadow map, in texels.
+
 .. _mjrf_setLightColor:
 
 `mjrf_setLightColor <#mjrf_setLightColor>`__

doc/XMLreference.rst

@@ -3301,8 +3301,8 @@ Attributes may be applied or ignored depending on the lighting model being used.
 .. _body-light-bulbradius:
 
 :at:`bulbradius`: :at-val:`real, "0.02"`
-   The radius of the light source which can affect shadow softness depending on the
-   renderer. This only applies to spotlights.
+   The radius of the light-emitting surface. Larger radii produce softer shadows in renderers that
+   support soft shadows. Ignored by the classic renderer.
 
 .. _body-light-attenuation:
 

doc/includes/references.h

@@ -3442,6 +3442,7 @@ mjrfLight* mjrf_createLight(mjrfContext* ctx, const mjrfLightParams* params);
 void mjrf_destroyLight(mjrfLight* light);
 void mjrf_setLightEnabled(mjrfLight* light, mjtBool enabled);
 void mjrf_setLightIntensity(mjrfLight* light, float intensity);
+void mjrf_setLightShadowMapSize(mjrfLight* light, int map_size);
 void mjrf_setLightColor(mjrfLight* light, const float color[3]);
 void mjrf_setLightTransform(mjrfLight* light, const float position[3], const float direction[3]);
 int mjrf_getLightType(const mjrfLight* light);