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Optical Illusions in Motion

This is still a work in progress.

This is the complete recipe, but more graphics will be added to help clarify some information.

Optical Illusion recipe

Open a New > Motion Project in Motion with the frame rate set to 60 and the length set to 10:00 seconds. [You can make this project in any format you like… but for the purposes of this tutorial, a plain project will do.] A frame rate of 60 is necessary to follow this tutorial. Timing is critical and 60 fps makes for smoother animations.

Draw a fairly good-sized vertical line starting from the lower part of the screen to the upper part.

You want to create the line so that the lower point is the starting point.

Select the Properties tab and reset the position so that it is center screen.
Go back to Shape > Geometry and set Point 1.Y to 0. Point 2.Y should be around 400 (but it doesn’t have to be exact.)

This will create a line with the anchor point at the starting point at center screen.

In Shape > Style, set the Outline > Width to 100 (this is completely variable and can be customized later if you like).

Go back to Properties > Scale. Set the Scale to 0%.
Right click on the Scale parameter and Add Parameter Behavior > Oscillate.

In Behaviors > Oscillate, set the Amplitude to 26% and the Speed to 24.
Amplitude can be customized later. Speed can be customized later, but these are the best starting settings for this project. Amplitude will control how “large” (long) the line will grow at the maxima and speed is set to 24 so that this project, with its framerate and length settings will loop seamlessly.

Play this setup. You should have a Line that grows upwards and shrinks to the center of the screen, then animates in the opposite direction. If you play through the whole project, the scaling animation will complete 4 full cycles. In this project, each cycle will be 150 frames long. You will see this number again.

I will suggest here that you select the Line object and type Command-Shift-G to create a New group containing the Line. The reason for this may not be all that obvious and may not be all that necessary. The reasoning is that the entire animation should be contained in only ONE parent group and if this part is skipped, then the project gets to be a little messy, and this next part is crucial because we need a Clone object.

Select the Group containing the Line object and type the ‘K’ key to create a Clone of the Line object.
If you just Clone the Line object (and turn off the Line visibility) and play the project, you will see that the clone does not display the animation of the Line! However, if you clone the Group containing the animated line, it does animate!

After Cloning the Line’s group, turn off the Group’s visibility.

With the Clone selected, type ‘L’ to Replicate the Clone.

If you look down in the Cell Controls section, you will notice options to Play Frames, Random Start Frame and sliders to control the playback of the animation. This is THE reason for cloning the Line object because now we have control over how this effect will be realized.

For this project, set the Replicator > Shape to Circle. Set the Arrangement to Outline. Set the Radius to 450. Set the Points to 150. In Cell Controls, check the Align Angle option. (You should see a “fat outline” circle).

To make this work as an optical illusion, we need to offset the Starting frame for the playback of EACH Cloned Line replicated. In Cell Controls, set the Source Frame Offset to 4. You should now see 4 “loops” in the graphic. Playing will appear to rotate the loops in a counter clockwise direction. If you go up to Build Style, you can make this go in the clockwise direction by setting it to Counter-Clockwise (“counter-intuitive”, but remember — this is an OPTICAL illusion! What you see is NOT what is happening).

Adjustments you can make are to Color, Scale.X; Go back into the Oscillate behavior and set the Wave Shape to Sawtooth (any of these are useable for differently “styled” optical illusions).

To create the 3 “segment” arrangement, go back into the Replicator > Cell Controls and set the Source Frame Offset to 3.

At this point, just for design consideration, you can duplicate the Replicator, reduce the Radius, swap the Build Style and adjust the Cell Controls Scale X.

Other customizations would be to tweak the Oscillate Amplitude and the Wave Shape. You can change the Shape of the Replicators. You can also change the First Point Offset and/or the Last Point Offset of the Line object which will change how the scaling animation appears. In music, there’s this thing called the Shepard Tone – an audio illusion of a continually rising pitch. With the Sawtooth oscillation, setting the First Point Offset to near 90% will create a visual effect of a continual contraction of the moving segments — you “get the feeling” that the image is always growing smaller even though it doesn’t!

Using the Square Wave Shape in Oscillate can be used to create an animated “Tech Ring” effect.

There are Parameter settings in this project that are related to each other – changing one changes the “behaviors” of the others.

If you double the Speed of the Oscillate, you will double the “segments” in the graphic. If you also reduce the Replicator Points by 1/2 after doubling the Oscillate Speed, you will restore the original arrangement. If you alter the Source Frame Offset, then adjustments to the other two parameters may be in order! If you build this project in a slower frame rate, all of these parameters will have to be readjusted across the board.

Okay — what if you change the frame rate of the project? For one, all of the major parameters involved will have to be adjusted based on the length of the project, basically, the total number of frames; the number(s) of replicated lines (Points), the Source Frame Objects and the Oscillate behavior Speed. Understanding that makes dealing with it easier. I would recommend keeping even multiples of 30 though. Luckily, Motion supports 30, 60, 90, and 120 frames per second, and even though 90 and 120 fps are not practical for playback, it’s not about speed, it’s about the “math” of the inter-related parameters. The higher the frame rate, the better the resolution and the easier adaptations will be. A frame rate of 30 virtually eliminates the three segment design this tutorial is based on with the minimum number of segments being four.