morphDragScrimFactor function
The scrim attenuation of a live drag: the factor the displacement multiplies into the scrim opacity - thinning with morphDragRecede and thinning further as morphDragArm rises. The one implementation of the composition, shared by the shuttle and the settled route page, so a drag dims identically on both sides of the second latch.
Implementation
double morphDragScrimFactor(double recede, double arm) {
return (1 - 0.5 * recede) * (1 - 0.35 * arm);
}