A ToonTalk picture touching more than one thing

Hi all.

For domains like eco modelling and physics the ToonTalk sensor "Touching 
Who?" is frequently used. It has long been noted that it doesn't deal 
well situations where a picture is touching more than one thing. Looking 
at the code I was surprised to discover that solution had been 
implemented about 5 years ago. The solution was buggy but easy to fix 
(and fixed in 3.127). The idea is that when you vacuum off what is on 
top of the Touching Who sensor you see the next thing that is touching.

To test this I made a robot that made a sound when a rectangle touched a 
ball and put it on the back the rectangle. I then arranged for the 
rectangle to touch a ball among many other things. Depending upon luck 
(actually the Z ordering of the objects involved) the sound occurred or 
not. But when I added a robot on the back of the rectangle that did 
nothing but vacuum off the top of the Touching Who sensor then the 
picture shown on the sensor changed on every cycle and hence the sound 
robot ran (but it might have to wait a few cycles to notice that it was 
touching a ball).

What is nice about this is that old programs should run the same as 
before (assuming they don't vacuum off a touch who sensor -- a check of 
the Playground Adventure games showed it still works as before and it is 
probably the most sophisticated program using sensors of this sort. It 
is only when a robot that vacuums off the top of the Touching Who sensor 
does the new behaviour kick in.

I admit this is a bit peculiar that you need to have this robot 
vacuuming the Touching Who sensor to deal with multiple collisions but 
it is the minimal change to ToonTalk to support multiple collisions. And 
there is a story behind it that kids should be OK with.

Comments?

Best,

-ken





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