Last week, a former student called with a question. He was trying to have a line draw on screen, from the top down. He did this by keyframing the scale and position of the line he wanted, but he found that his line kept wanting to scale from the top and bottom instead of just from top down.
There are two solutions to his problem, and both are important enough that I wanted to share them with all of our readers interested in Motion. First, he could use the shape's anchor point to fix his problem with scaling. But there's also a completely separate approach to this problem, that might be more useful.
There are two solutions to his problem, and both are important enough that I wanted to share them with all of our readers interested in Motion. First, he could use the shape's anchor point to fix his problem with scaling. But there's also a completely separate approach to this problem, that might be more useful.
A shape's anchor point determines where everything else "happens
from." Everything in your composition has an anchor point, and by
default, the anchor point on any layer starts out in the middle of that
layer. That's why, when you scale or rotate a layer, it'll normally
grow or shrink into the middle of that layer, or rotate around the
middle.
In this case, the former student wanted to have the line "grow" from the top of the line, instead of the middle of the line. I suggested that he use the Anchor Point tool to click and drag the line's anchor point to the top of the line.
Compared to scaling lines up, this approach also lets you stay more organized as you composite: you can paint all the shapes and lines you want, and leave them in their final positions. By simply animating the path's percentage, you can avoid all sorts of messy repositioning -- and strip out a lot of complexity from your key framing.
In this case, the former student wanted to have the line "grow" from the top of the line, instead of the middle of the line. I suggested that he use the Anchor Point tool to click and drag the line's anchor point to the top of the line.
But there's a better way still. In Motion, the preset "shapes" work the same as custom shapes and paths -- the same sort of shapes you
could draw on by hand using the Paint tool. And if you look in the Shape Inspector for any shape, you'll see that every shape's outline has controls
for First Point Offset and Last Point Offset. By default, those values are 0% and 100%
respectively -- so you see the entire outline. But you can key frame the Offset controls to "paint on" or "paint off" shapes or lines
that are much more complicated than a single straight line: to paint
something on, for example, you'd just key frame the Last Point Offset control from 0%
to 100%.
Compared to scaling lines up, this approach also lets you stay more organized as you composite: you can paint all the shapes and lines you want, and leave them in their final positions. By simply animating the path's percentage, you can avoid all sorts of messy repositioning -- and strip out a lot of complexity from your key framing.
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