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NOVEMBER 15, 2002 Windmill In this tutorial, we’ll look at how to parent objects in After Effects and how the Parent-Child relationship works. Next time you are in the local mall, or shopping center look around and see how parents and children are moving. When parents go to the store, a lot of them tether their child to their arm. As the parent moves around the child must move with the parent; wherever the parent goes, the child must follow. As is often the case, children who are tethered still want to run around. The child can spin, jump up and down, move freely in his or her own space, yet no matter how much the child wants to run down the next aisle, that motion is not transferred back to the parent. [an error occurred while processing this directive] That way of thinking also applies to After Effects. Let’s create several simple windmill blades and parent them to a Null Object so they all rotate together. Step 1: Open After Effects and create a new composition. Name the project Windmill, using the D1/DV NTSC preset. Set the duration to any length you want. Step 2: Press Command+Y on the Mac (Control+Y for you PC users) to create a new solid. Name the solid Blade. Set the width to 25 and the height to 100 pixels. Give it any color you like, possibly a nice yellow.  The Blade layer will act as the child in this example. However it needs a pivot point to rotate around and to act as the parent. Step 3: Create a Null Object by going to Layers>New>Null Object.  Step 4: With the Blade layer selected in the Timeline, press the P key on the keyboard to activate the Position property for the layer. Change the Y-axis position to 340. The way any layer is set up when created, is to have the Anchor Point in the exact center of the layer. The Anchor Point determines where all Position, Scale, and Rotation transform changes will be centered. In order to set up numerous other blades around the Null Object and ensure that they remain in a perfect circle, you need to move the Anchor Point. To do this easily, use the Pan Behind Tool (keyboard shortcut Y). Step 5: Press Y on the keyboard to activate the Pan Behind Tool. In the Comp Window, click and drag the Anchor Point of the Blade layer so it rests at the same position as the Null Objects Anchor Point.  Step 6: Let’s make this a 6 bladed windmill. Duplicate the Blade layer five times by pressing Command+D (Control+D on the PC).  Step 7: Highlight all of the Blade layers. With all of the Blade layers selected it is very simple to parent the blades to the Null in one move. If you don’t have the Parent column in the Timeline visible, right click on the top of the Switches/Modes column and select Panels>Parent from the floating menu.  Click on the Parent Drop Down menu for the first blade layer and select Null. Since you have multiple layers selected the changes made to one will change all of the other selected layers.  Step 8: With all of the layers still selected press the R key to activate the Rotation property for the layers. Step 9: Now deselect all of the layers and for each layer change the Rotation values as follows Blade 1: 0 Blade 2: 60 Blade 3: 120 Blade 4: 180 Blade 5: 240 Blade 6: 300 Step 10: If you click on the Null Object and activate the Rotation transform property for that layer (R key), and rotate it, you will notice that all of the blades follow along. This is how the parent in this relationship controls all of the children. Create a beginning keyframe at 0. Set the Rotation value for the Null object to 0. Move to some other portion of the timeline and create another keyframe by changing the Rotation value of the Null object to 720. When you make a RAM preview you will see that all of the blade layers rotate and take on the same property characteristics as their parent - the blade layer. When not working deep in the labs of the DMN Central Division testing the latest and greatest software/hardware products Stephen Schleicher can be found at the local university teaching a few courses on video and web production. He can be reached at schleicher@mindspring.com. You can also visit him on the web at www.mindspring.com/~schleicher
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