Reflection

Reflection is light bouncing back off a surface. On a mirror-smooth surface it returns in one direction and forms a crisp image; on a rough one it scatters, so the reflection blurs or survives only as a soft sheen. Render engines handle every case between those extremes through the material’s roughness value.

The Fresnel effect

How strongly a surface reflects depends on the viewing angle. Look straight down into a lake and you see the bottom; look across it from the shore and it mirrors the sky. This behaviour, the Fresnel effect, applies just as much to glass facades, timber floors and lacquered panels. Physically based materials calculate it automatically, while a fixed reflection value set by hand makes surfaces look artificial.

Reflection in architectural rendering

• Sky and neighbouring buildings reflected in a glass facade place the building in a real context.
• Slightly blurred reflections on polished floors add depth to a room.
• In bathrooms and kitchens, tiles, chrome and mirrors are the details that set the quality of the scene.

Reflective surfaces also reveal mistakes: empty space behind the camera or half-finished objects show up in a mirror. For rooms full of reflective finishes, see our bathroom rendering tips.