Blocking guide
How the numbers were worked out
Everything in this guide comes from straight lines, a set of body sizes and the courts as specified. Here is what it assumes and what it leaves out.
The model
- The player is a few rounded rods: a head, a torso, two legs and two arms, in a set pose. The feet stay on one spot in every pose.
- Sight runs in straight lines from one eye point. A point is hidden if the line to it passes through a rod. The receiver stands still while the sums are made.
- The ball has gravity and no air. Off a wall or the floor it follows the sums of the angles guide, with the middle ball and no spin.
- A return is one aimed line from the hand. It is open if it clears every body by 1 ft or more, tight if it clears by less, and shut if it would touch.
The settings
- Height 5.9 ft. Eye 5 ft up, in a ready crouch. Shoulders 1.5 ft wide at 4.9 ft up. Hips 3 ft up. Torso 0.8 ft deep. Arm 2.4 ft long.
- Feet 1 ft apart upright and 3.5 ft apart in a wide stance. Legs stay the same length, so a wide stance lowers the hips. A lean tips the body 25° at the hips. A hop is 3 ft.
- Ball met 3 ft up for drives and lobs, and 1.5 ft up for kills and pinches, 1.6 ft out from the feet. The ball's radius is taken as 0.08 ft.
- Drives at 60 ft/s, kills and pinches at 70, ceiling balls at 50 and lobs at 40, measured across the floor.
- Courts, from the court specifications: One-wall 20 by 34 ft with a 16 ft wall and the short line 16 ft out; Three-wall 20 by 40 ft with a 20 ft wall and the short line 20 ft out; Four-wall 20 by 40 ft with a 20 ft wall and the short line 20 ft out; 60×30 30 by 60 ft with a 27 ft wall and the short line 32.5 ft out.
These are a grown player of ordinary build, not a measurement of anyone. A taller player hides more, and a receiver who stands taller sees more. Change the sizes and the numbers change, so read every number as "about" and "for this case".
What it leaves out
- Two eyes and a moving head. A real receiver leans and sways to see round you, and sees a little more than one fixed point.
- The receiver moving at all, which is the first thing a receiver does.
- The air, spin, and the scatter of real shots. A real ball does not follow one line.
- How hard a shot is to play. Being crowded can weaken a shot or make it less accurate, but the model only measures the room for the swing, not what the lost room costs.
- Reading the play from your swing, your feet or the sound of the ball.
- Every judgement a referee makes. Geometry can show what is hidden. Only the referee decides what is a hinder.
The script
The model is a short program in this site's source: web/scripts/guide/blockingModel.ts, with tests (blockingModel.test.ts) that check each direction this guide states. Run web/scripts/guide/blockingTables.ts to print its tables.