Reflection probes

since 0.4.3 Light and environment

Open the live demo · Read the source · View on GitHub

An environment map is the sky, or a picture somebody loaded, seen from nowhere in particular. A shiny car in a garage does not want the sky. It wants the garage: the workbench, the door, the light coming through it. A reflection probe is the scene itself, captured into a cube from one point, so a mirror finish shows the room it actually stands in.

Step 1: Put a probe where the reflection should come from #

ReflectionProbeNode is a point in the scene. On the first frame it is seen, the renderer draws the world into the six faces of a cube from that point, then blurs the cube once per roughness level so a duller surface reads a softer version of the same room. Add it like any other node.

_probe = ReflectionProbeNode(name: 'probe', intensity: intensity)
  ..setPosition(0.0, 0.9, 0.0);

intensity is its own knob, separate from the scene's flat ambient light: a probe is the room's light already measured, so a dim room reflects itself at whatever strength it was actually lit.

Step 2: Give something a mirror finish #

A physical material reads the nearest probe automatically once one is in the scene. High metallic and low roughness make the read obvious: a rough ball barely shows the room, a polished one shows it sharply.

final Material ball = _ball = Material(
  name: 'mirror ball',
  baseColor: Vector4(0.9, 0.9, 0.92, 1.0),
  metallic: 1.0,
  roughness: roughness,
);

Drag Ball roughness down and the wall and the floor around it become readable in the reflection; drag it up and the same room becomes a soft smear of colour.

Step 3: What actually happened on the device #

The capture is not free, and it does not run every frame for a probe that is not moving. Probe intensity and Ball roughness are read fresh every frame, so a control here only has to change a field.

@override
void update(DemoContext context, double dt) {
  _probe.intensity = intensity;
  _ball.roughness = roughness;
}

Note. The first frame a probe is seen, the renderer draws the scene six times into its cube and then filters the whole chain. A kept probe after that draws nothing again until invalidate() is called or the scene changes what it can see.