Appends terrain depth to every cascade of the directional shadow map produced
by the engine's ShadowFeature. shadow:cascades is set during ShadowFeature's
update() but the engine wipes frame.extras between update and addPasses,
so it is cached in our own update(). Skips quietly when there is no shadow
map, no cascades, or no terrain.
Appends terrain depth to every cascade of the directional shadow map produced by the engine's ShadowFeature.
shadow:cascadesis set during ShadowFeature'supdate()but the engine wipesframe.extrasbetween update and addPasses, so it is cached in our ownupdate(). Skips quietly when there is no shadow map, no cascades, or no terrain.