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Setting a destination location using a null object?

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Thomas Hannen
Setting a destination location using a null object?
on Mar 14, 2011 at 8:42:14 pm

Hi,

I need to make a cross-hair animation (in 2D), pinpointing various locations on a map. Two lines (horizontal & vertical), and a square where the lines intersect, will fly in from the edges of the screen, pinpointing a map location.

So far, I've been manually animating each location - setting the start and end positions of each object by hand.

Is there a way that I could set a destination co-ordinate, using a Null Object, so that each time the lines fly in from the edges of the screen, they end up at the null object position? I've tried setting the line position by connecting them to the null object (using an Expression connected to the position coords), but it affects all keyframes in the track, not just the second keyframe.

Any advice appreciated!


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Dave LaRonde
Re: Setting a destination location using a null object?
on Mar 14, 2011 at 9:15:28 pm

I'd do it by making two solids to to form the horizontal lines that are way longer than they need to be, at least twice the width of the comp. The same thing for the two vertical lines. Create a null object at dead-center screen, then position the lines & square to line up as desired.

Now -- and ONLY now -- parent lines & square to the null. Create ENDING keyframes for the motion, opacity, etc. Go back in time and make the beginning keyframes.

Now you simply duplicate all these layers, and make sure the new lines & square are parented to the newly-duplicated null. Move all of them to the point in time where they should appear. Move the null to the desired point. Now just move the beginning keyframes for the moves so they're just off screen.

Repeat as necessary for the remaining points on the screen.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Thomas Hannen
Re: Setting a destination location using a null object?
on Mar 14, 2011 at 9:24:18 pm

Great advice -many thanks!


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