Still haven't gotten net access at home, so I have to respond privately
to this (meaning Bruce Nevin 980114.1838 EST)
It might not be so simple to compare the 2-D and the 3-D models in this
regard. One idea: if the fielder's run to the catch point does in fact
trace an arc, project a tangent from the starting point of the runner's arc
to the plane of the ball's trajectory. ...
To this I'd like to add an idea: If you draw a tangent of the arc of
the run make the length of the line indicative of the fielder's
_accelleration_ in said direction.
Tracy Harms <snarl@hackvan.com> (Thu, 15 Jan 1998 09:29:42 -0800) --
(Offline message quoted conventionally below.)
I wasn't proposing an enhancement to Rick's demo, but a way of visualizing
how the "backup" effect might have a different appearance when there is
lateral motion, and until we had done the comparison we couldn't be sure
that the backing up had gone away or been reduced. I suppose displaying it
might be useful if you are comparing the 2D and 3D models, but in a 3D demo
I think it would be confusing.
Backing up looks like a means of controlling the perceived vertical
velocity of the ball, which is what Rick told us is going on:
Rick Marken (980113.2150) --
The reference
for the controlled perception (angular velocity) is positive so
the fielder's movement's are aimed at keeping the perception
of the ball moving upwards at a constant rate on the retina.
How do we (as living baseball catchers) distinguish a high popup from a
ball hit high and long? Maybe a fielder perceives the expanding size of the
disk-image of the approaching ball, but that seems difficult. I expect that
a skilled fielder might look for deceleration towards the top of the
trajectory. The popup starts decelerating pretty soon; the long fly keeps
rising longer. Watch for fielders to run laterally or forward for popups
that infielders catch. And of course actions of the infielders are other
indicators.
I didn't see any high, short popups in the demo. Probably didn't run it
enough. Maybe at Willy Mays speed the fielder snatches them from the
shortstop or the pitcher or even the catcher in this model.
Bruce
Rick and Bruce,
Still haven't gotten net access at home, so I have to respond privately
to this (meaning Bruce Nevin 980114.1838 EST)
It might not be so simple to compare the 2-D and the 3-D models in this
regard. One idea: if the fielder's run to the catch point does in fact
trace an arc, project a tangent from the starting point of the runner's
arc
ยทยทยท
At 09:29 AM 1/15/98 -0800, Tracy Harms wrote:
to the plane of the ball's trajectory. ...
To this I'd like to add an idea: If you draw a tangent of the arc of
the run make the length of the line indicative of the fielder's
_accelleration_ in said direction.