Hardware lab 02 · Optical pointing
How the Wii Remote sees infrared light
Aim, roll, move, and obstruct the controller. The bench exposes the camera image and the geometry that turns two light blobs into a screen coordinate.
A 1024 × 768 IR camera detects up to four bright blobs.
Live optical bench
- BLOBS
- 2 / 4
- MIDPOINT
- 511.8, 384.0
- SEPARATION
- 111.9 px
- ROLL
- 0.2°
- CONFIDENCE
- 99% TRUE PAIR
Move the physical system
These controls change the camera-to-emitter geometry. The sensor data is recomputed from a pinhole-camera projection.
Break the optical signal
YAW
PITCH
ROLL
DISTANCE
Keyboard: arrows aim · Q/E roll · W/S move nearer/farther.
Calibration target
Calibrate while centered, then aim the controller until the green crosshair reaches the ring.
456 px ERROR @ 1080p
Calibration: FACTORY · estimated distance: 221 cm · FOV edge margin: 384 px
Camera report
Extended-mode style packet: 3 bytes per blob. X and Y high bits share the third byte with a 4-bit size value. Empty slots are FF FF FF.
C8 80 5F 38 80 6F FF FF FF FF FF FF| Slot | Raw X,Y | Size | Ground truth |
|---|---|---|---|
| #0 | 456, 384 | 15 | bar-left |
| #1 | 568, 384 | 15 | bar-right |
| #2 | 1023, 1023 | — | empty |
| #3 | 1023, 1023 | — | empty |
1 · PHOTONSTwo LED clusters emit infrared light.
2 · CAMERAThe remote finds bright centroids in a 45° × 35° field.
3 · REPORTBlob coordinates and sizes become bytes, not a finished cursor.
4 · GEOMETRYMidpoint estimates aim; separation estimates distance; line angle estimates roll.
5 · SOFTWARECalibration maps camera coordinates to the television.
What to notice
- Covering either LED cluster leaves one blob—insufficient for roll or distance.
- Moving farther away reduces blob separation according to perspective projection.
- Twisting the remote rotates the line between the two detected centroids.
- A lamp or candle can become a false IR source and confuse a geometry-only pairing heuristic.
- The camera reports light locations; the console software decides what they mean.
- Yaw or pitch beyond the field of view removes the blobs even though the sensor bar is still emitting.