"See?" Sol said. "You didn't add anything. You just stopped pretending every surface is equally blessed by the sky."

"What does it do?" Lena asked, skeptical.

The cabin looked heavy now. The underside of the deck was a rich, soft charcoal, making the boards above feel solid and real. The gap between the siding and the stone chimney was no longer a white line—it was a deep, welcoming crevice. The window frames, which had looked pasted on, now seemed to sink naturally into the wall, because a subtle darkness pooled in their reveals.

She never built a SketchUp model again without first whispering to those tight corners. Because she had learned the architect’s oldest truth: light defines what we see, but darkness defines what we feel . And Ambient Occlusion was the fastest way to teach a computer the difference.

Sol shook his head. "Sun is a gossip. It tells you everything on the surface. You need a secret-keeper. You need Ambient Occlusion."

Under the first, she wrote: Geometry.

And yet, the image on her screen looked like a cardboard cutout.