TL;DR: Aim at the half-ball point — cue tip strikes the side of the object ball such that the line through the contact point passes through the centre of the cue ball. Produces a known cushion-bounce angle (~30°), used as a calibration reference for system-shot estimation.
How to identify the half-ball point
- Look at the object ball
- Aim cue tip at the side edge of the object ball (not the centre)
- The cue ball will hit half of its surface against the object ball
- Cue ball will deflect at ~30° from its original line
Why use it
- Standardised reference angle for system math
- Predictable post-contact cue ball trajectory
- Calibration: if your half-ball produces an off angle, table conditions differ from system assumption
Half-ball + english combinations
| English | Approximate post-contact angle |
|---|---|
| None (centre) | ~30° |
| 1 tip running | ~25° |
| 1 tip reverse | ~38° |
| Heavy follow | ~26° (post-impact follow) |
Limitations
Half-ball assumes consistent ball cleanliness, cushion firmness, and stroke speed. On dirty balls or worn cushions, the angle drifts ±2-3°.
Calibrate in 3ball
Run 10 half-ball shots in the simulator. Compare predicted vs actual angle to find your calibration offset.
Open 3ball →