Animating a worm gear using shadows

Worm gears look like big screws with spiral threads, but without a screw head on the top. They’re used in equipment and machines where strength is an important factor because they are very durable and can handle a lot of torque. Here is a typical worm gear:

Figure 7.3: A worm gear

If we add a worm gear image to the project and animate it as we did with the round gear, it wouldn’t work very well, simply because the worm gear image is not a round shape. So, how can we make an irregularly shaped image appear like it’s turning as it would in the real world?

What we can do is place small, shaded rectangles over the shiny parts of the worm gear image and animate those rectangles instead, which will create the illusion that the image is turning or spinning. Clever, right?

First, create a new file, choose the SwiftUI View template, and name it WormGearView. Inside this file, within the WormGear struct...