The saved lab computes shear as gas density times shear velocity squared. With the stored density one point two two five, velocity one gives one point two two five and velocity two gives four point nine, a factor of four. At sixty pixels per calculated shear unit the widths are seventy three point five and two hundred ninety four. The displayed dimensionless ratios divide that shear by selected grain density, gravity and diameter combinations. This explains the code formula rather than proving laboratory accuracy or a scientific transport law. The external Matter physics engine must load before this page initializes controls, and it is unavailable in the offline test. The critical threshold function is piecewise. Below Reynolds value zero point zero five it returns two. At exactly zero point zero five, the next branch returns zero point four plus zero point three divided by zero point zero five, which is six point four. At zero point five the following branch returns zero point one two plus zero point one five divided by zero point five, or zero point four two. At forty pixels per returned unit, those widths are eighty, two hundred fifty six and sixteen point eight. These branch jumps are explicit code behavior; the video does not smooth them or endorse them as a validated empirical curve. The particle radius on screen is a logarithmic mapping from diameter fifty micrometers through two millimeters into three through sixteen pixels. At the lower endpoint the drawn radius is three, and at the upper endpoint it is sixteen. At twenty pixels per illustrative radius unit the comparison bars measure sixty and three hundred twenty. Physical mass is computed separately from grain density times four thirds pi times half diameter cubed. Doubling physical diameter therefore multiplies mass by eight, while screen radius follows a different logarithmic scale. Visual size is not a physical measurement, and simulated flux is a proxy from lifted-particle count rather than independently verified sediment transport.