Kinematics refers to the motion of objects and can be split into two types:

Forward Kinematics – this type of animation focusses on moving links or joints individually and they tend to move in arced directions.

Inverse Kinematics – this type of animation focusses on the main parent joint and the end child link to create movement as the child links in-between move in relation to the end-point or which joint you move. This type is more linear in its movement.

In adobe after effects, we were using forward kinematics to animate a swinging chain.

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First, open photoshop and create a new HDV 1080p document under Film & Video and set the resolution 150px.

 

Create a new layer and name it c1 before finding the chain brush in the brushes dropdown.

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Draw a single chain, select it and rotate it by 90° so that it is upright.

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Now, with the chain link selected, use the shortcut CMD + J to duplicate the layer. Each time change the layer names to c2, c3 etc. until you have at least 5 chain links.

 

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As you duplicate the layers, arrange them beneath one another.

 

 

Now open Adobe After Effects and select ‘New Composition From Footage’ and find your psd file of the chain. When selecting the psd file, ensure that enable is set to ‘all acceptable files’ and that Import as is set to Composition – Retain Layer Sizes.

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This will create the chain link as a composition in your library so double-click to enter it. This was the setup.

 

Using the anchor point tool (shortcut A), move the anchor point of each chain link to the top so that when rotating, they move from the correct point.

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After this, you’ll need to create the parent-child link between the chains by using the parent pick-whip tool in the timeline. Do this by clicking and dragging from the swirl icon to the chain layer underneath for each layer. The first layer that you start with will become the parent joint whilst the rest will be child links. Now open the rotation option in the timeline (shortcut r) and press the stopwatch to enable animating.

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To make the chain swinging look more naturalistic, you can open the graph editor to add easing.

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When you open the graph view, the lines, from point to point, will be straight so you need to find the ‘easy ease’ button to apply ease in and out to your animation.

 

After doing this, the lines will become curved and resemble a sine wave and watching back, there will be easing in and out in your animation.

Here is an animated gif of my animation:

chain link

 

I feel that the swing looks the most natural in the beginning and that I could’ve added more height to the swing to make the animation more interesting. I can also try to add something to the end like a wrecking ball or a basket to add more substance to the animation.

 

sources:
http://what-when-how.com/advanced-methods-in-computer-graphics/kinematics-advanced-methods-in-computer-graphics-part-1/