Pool.bzDraw it first
Two short exercises for the diagram desk. The drawing is a plan, not a prediction of how a real table will play.
Drill 1: find the contact point on one cushion
Place a cue ball and an object ball a few diamonds apart, away from the rail. Pick a point on the playing surface as a target for a one-rail path. In the ideal point-ball model, reflect that target across a straight cushion line. A straight line from the moving ball to the reflected target meets the rail at the proposed contact point.
- In the diagram desk, place the starting balls. Draw a segment from the starting center to the proposed rail point.
- Draw a second segment from that rail point to the actual target. Compare the two angles relative to the rail normal.
- Move the starting ball half a diamond, undo, and try a second line. Export both diagrams for side-by-side comparison.
What changes on a real table? A finite ball center contacts a line offset from the cushion nose. Cushion response, speed and spin can change the outgoing path. The diagram desk does not infer those parameters or certify that a bank will go in.
Drill 2: explain the cut without hiding the cue ball
Place an object ball away from all pockets and pick a corner. Draw a line from its center to the pocket. In an ideal frictionless collision, a ghost cue-ball center lies one ball diameter back from the object-ball center along the opposite direction of that line.
- Mark that candidate contact position with a temporary ball or arrow endpoint.
- Draw the cue ball’s line of approach to the candidate center, not to the center of the object ball.
- Look for an obstructing ball along the entire swept path. A line has zero width; the ball does not.
Export the diagram before trying the shot. The game is a separate local table: it does not import a diagram as a match or reconstruct an old session.