# Animating a Rotating Wheel on a Slant?

We're constructing a simulation of a film projector. We would like to rotate the shutter, which is essentially a wheel on a slant in the simulation:

We can create a series of intermediate images in a CAD program and then import the sequence into Snap! as a series of costumes.

However, is there a straightforward way to do this entirely in Snap! ? (Thanks)

create a flat version of it (just the 2d front surface and make a clone of it slightly behind and to the right
as long as none of the parts of the costume are too thin (the image here looks fine) it should work, although not with the slight shading here

Thanks ... we'll give it a try.

If the issue is that you can't just attach the picture to a sprite and rotate the sprite because the picture is an ellipse rather than a circle, make a circular version, rotate that, stamp the rotated version onto another sprite, then use the STRETCH block (in Looks) to make an ellipse of it by shrinking the X value.

The issue is that the perceived geometry changes as the disk rotates. We know how to adjust the geometry in a CAD program like Solidworks, but we don't know how to do it in Snap! (possibly because, unlike some on the forum, we didn't pay attention in math class). Here's a link to the disk rotating in Snap!

We assuming that if we knew the correct geometry for a given slant, we could make the appropriate adjustments using "Stretch - X" and "Stretch - Y". Likely one of the math educators on our campus could tell us, but we thought that we would check in the forum first. .. Thanks

P.S. This is one of the many things that I like about Snap! In any project, there are almost always interesting discoveries. (Plus, it is even more fun when it is not required homework. Choice = agency.)

Okay, here's my solution. First I turned your ellipse into a circle:

and selected that costume.

Then I made a new sprite, and set its costume to a big white square.

Then in the first sprite I ran this:

The first TELL clears the big white square. Then the key is the PASTE ON, which makes a costume equal to the original (circular) one, but with its current rotation built in. Then the second TELL turns it back into the original ellipse shape.

This is really interesting ... tomorrow I'll put together a prototype of the projection animation.

Our plan is to invite the students in a maker class to create a digital model in Snap! and then construct a parallel physical model that displays the same animation. We're still exploring how this might work ... we'll post details for feedback and comments as it progresses. (As always, thanks!)