Stone in shade
Steep rock in shadow went almost black. A little bounced sunlight gave it its shape back.
Mountains are the backbone of an Eras island, and in the afternoon half of every one of them sat in its own shadow. The shaded side went nearly black: a flat dark shape with no folds, no ledges, nothing to read. Up close it looked like a hole in the world.
Why shade went black
In our renderer, a surface in shadow gets light from only one source: the sky. The sky is a dim, blue light from above, and a steep rock face hardly faces the sky at all. So it got almost nothing.
Real rock in shade isn't lit by the sky alone. The meadow at its foot is in full sun, and that sunlit ground throws some of the light back up onto the rock. Painters lean on this all the time: shadows have color, and a shadow next to a bright field is never black.
Light from the ground
Now steep ground gets a share of the sun's light back, as if bounced off the field below. It's the sun's own color, half greyed so the stone keeps its hue, with a touch of the ground's warmth. It scales with how strong the sun is and turns off at night. Faces that lean sideways or down, toward the ground, get the most.
It goes in as light, not as paint. The bounce multiplies the rock's own color, so dark stone stays dark stone, only readable. We tried three strengths. At a third of that, nobody could see it. At nearly double, the shadow side went flat and grey and lost its contrast with the lit side. We settled in between.
Only up close
From far off, a dark mountain against a bright sky is exactly right. It's the silhouette that tells you where you are. So the bounce fades out between 350 and 600 m from the camera. Mountains on the horizon keep their dark outlines, and only the rock you're walking under opens up.
You can see what's next in the shot above. The summit's shadow has a stepped edge where it falls across the wall, and that's on our list.
This is live now, along with a pass on the small things: stones each a little warmer or cooler with moss on their damp tops, flowers in their true colors, and every tree its own green.