Add motion blur to animated layers

The goal of this script is to turn on the motion blur switch on all layers that are animated in the currently open After Effects composition. This tutorial goes through the script line by line, explaining what each line does.

Create a wrapping functions, so no variables or functions gets added to the global after effects scope. And include the aequery library

( function () {
	//@include path/to/aeq.js

Get the currently open After Effects composition using aeq.getActiveComposition.

	var comp = aeq.getActiveComp();

aeq.getActiveComposition returns null if there is no composition open. So stop the script if that is the case.

	if ( comp === null ) {
		return;
	}

To be able to undo the action of the script, by using edit > Undo from the menu or the ctrl/cmd + z keyboard shortcut we use the aeq.createUndoGroup function. The function takes three arguments:

• The name of the undo group. Visible in the Edit menu.
• A function to execute. In this case, we are passing in the addMotionBlurToCompLayers function.
• An array of arguments to pass to the function. In this case the function needs a comp as the first argument, so we create an array with the variable that contains the currently open comp.

	aeq.createUndoGroup( "Add motionblur", addMotionBlurToCompLayers, [ comp ] );

Now we need to create a function that looks for layers to apply motion blur to.

	function addMotionBlurToCompLayers( comp ) {

The first thing the function does is to loop through the layers of the comp for layers without any motion blur using aeq. To search through only the comp passed to the function, we set comp as the context parameter in the aeq function.

Since the aeq function returns an aeq.arrayEx object, we can use aeq.arrayEx.forEach to loop through all the layers

		aeq( "layer:not(motionBlur)", comp ).forEach( function ( layer ) {

We are now looking at a layer and need to find out if the motion blur switch should be on or not. For that we loop through all the properties, and look for one that is animated, using aeq.forEachProperty.

			aeq.forEachProperty( layer, function ( property ) {
				if ( property.isTimeVarying ) {

Since the property and therefore the layer is animated, we want to enable motion blur on the layer and any layer that has this layer as it parent. To that we use a specialized addMotionBlur function.

					addMotionBlur( layer );

Since we have added motion blur to the layer, we can stop looking through all the properties. To do this we return false which stops the forEach loop.

					return false;
				}
			} );
		} );
	}

Now comes the function that actually applies the motion blur.

	function addMotionBlur( layer ) {

We want to apply motion blur to more than only the layer passed to the function. We want to apply it to all layers using the layer as a parent, because if the parent layer moves, the child layer also moves.

So we need to get all the child layers, and to do this we use aeq.layer.children. Then we loop through them and do the addMotionBlur function recursively for all the children.

		var children = aeq.layer.children( layer );
		aeq.forEach( children, addMotionBlur );

Now we actually set the motion blur attribute of the layer, but we only want to apply motion blur to layers that can have motion blur enabled. For example cameras and lights do not have motion blur attribute. And there is no use in having motion blur on null layers, so we check that first, before setting the attribute.

		if ( layer.motionBlur !== undefined && !layer.nullLayer ) {
			layer.motionBlur = true;
		}
	}

Then, finally, we close the wrapping function

}() );

Here is the whole script we just created:

( function () {
	//@include ../dist/aeq.js

	var comp = aeq.getActiveComp();

	if ( comp === null ) {
		return;
	}

	aeq.createUndoGroup( "Add motionblur", addMotionBlurToCompLayers, [ comp ] );

	function addMotionBlurToCompLayers( comp ) {
		aeq( "layer:not(motionBlur)", comp ).forEach( function( layer ) {
			aeq.forEachProperty( layer, function( property ) {
				if ( property.isTimeVarying ) {
					addMotionBlur( layer );
					return false;
				}
			} );
		} );
	}

	function addMotionBlur( layer ) {
		var children = aeq.layer.children( layer );

		aeq.forEach( children, addMotionBlur );
		if ( layer.motionBlur !== undefined && !layer.nullLayer ) {
			layer.motionBlur = true;
		}
	}
}() );