Creating directional constraints for eyes


When rendering out characters, most times it's preferable to have them looking straight at the camera. But you may need to move the camera around quite a bit so that you can get just the right angle, which means, you will need to keep manually adjusting the eyes so that they continue to look towards the camera. There is a way though that you can constrain the eyes to remain fixed on a particular spot (locator). That way you can then move the locator anywhere around and the eyes will follow, making it a lot easier for you to set up your shot.

If however, you move the locator really close to the eyes, they will go cross-eyed, so using a central controller can help deform the eyes in a non-destructive manner.


    Prepare eyes

    • Turn on deformations by pressing O.
    • Select Enable Deformers so they are visible to the camera
    • Put each eye into separate Item mesh layers
    • Select each eye Item individually and center pivot points inside each eye > Edit > Center to Bounding Box > Center

    Setup Tab

    • Select the Setup tab up the top and then press the Setup button (the viewport will be highlighted) - this effectively turns off deformations temporarily. Leave it on until the end.
    • Select one eye at a time, under the Commands menu > Deformers > Transform  . This will add a transformer inside the eye item. It will also create a Transform Effector, which essentially is a locator that the eye will become constrained to.
    • Rename the Transform Effectors Left & Right. As they will both be created in world space sitting at 0,0 they'll be difficult to tell apart.
    • Making sure that the eyes are visible (i.e. hide any distracting layers), from the Item List
    • Select one Transform Effector at a time, and while Match Position is selected, click on Drop Action and then drag'n'drop into each eye.
    • You can reduce the size of these Effector locators under  > Display > 3D Items > Size 
    • Select both locators and duplicate them, and then move them to out in front of the face.
    • Duplicate one of those locators and move it hoizontally so that it's in between the two.
    • Parent the locators to the central one which is now effectively the main controller
    • Now we need to create a directional constraint by selecting the left eye transform locator, and then shift-clicking on the left locator out the front.
    • Under the Modifiers tab, select Direction. Repeat with the right eye.
    • To test that it works, turn off Setup mode.
Source  You can watch a video that details the process here
Author  Daniel Ripley - cgdreams.co.uk
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