Monday, April 11, 2022

Nested sprites in Snap!

There is a Swimmer in Snap Examples which features 13 sprites attached to each other but I wanted a simpler example to teach to new Snap learners.

Read page 10 of the Snap! Manual for an overview of Sprite Nesting: Anchor and Parts:
Sometimes it’s desirable to make a sort of “super-sprite” composed of pieces that can move together but can also be separately articulated

I asked in the Snap Forum and cymplecy made a few suggestions: a car spinning its wheels, a Ferris wheel or a face blinking its eyes or moving its mouth.



Cymplecy observed that it's easier to do this in Snap! than Scratch.

Set the car pivot point half way between the 2 wheels and horizontal with the centres of the wheels. Otherwise, the wheels will spin out when you bounce off the wall.

I made the wheel by duplicating the car and rubbing out everything except one wheel. Set the pivot point of the wheels in the centre of the wheel, of course.

I reset the spin direction of the wheels to correlate with the car direction. It also works fine if you change the size of the car.



If teaching this to beginners I'd give them the wheel and carriage to start with and teach the sprite nesting technique. The parts have a synchronous / dangling flag. The dangling option works well here, as the wheel rotates.

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