CC Sphere Earth Again
I watched a a couple of tutorials on creating a 3D earth for my project. I saw the one on Creative Cow, that looked like the thing I was after. But the problem with that, is that I have to control the radius of the whole globe, in a way that the cloud and athmosphere layers grow, or shrink the same way as the texture layers wich can be linked togeather easily, because they have the same radius. I'm a beginner in After Effects, so I'm not really an "expressionist", but my idea is that there might be a way to do this. In my case the radius of the texture layers is 200 just like in the tutorial, and the clouds layer has a radius of 202. 204 for the athmosphere. Id like to set up the thing so, that when I change the radius of the texture layers to 400 then the cloud layer should have a radius of 404, and the atmosphere has it at 408. When I set the textures radius to 2000 then the others should have a radius of 2020, and 2040. So the layers realation in diameter is always the same percentage. How can I link these together. By the way I want to do this because I'd like to make a an earth zoom scene far away from space,ending with a pretty closeup wiew of my country.
If I were doing the animation, I could either waste my time trying to figure out an appropriate expression, or I could simply keyframe the layers appropriately and be done in two minutes.
But that's just me....
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
if you know exactly what your after, dave's method is definitely the way to go.
but if you may have to change this animation or just want to learn a basic way to set this up, it's pretty simple.
i would first create a null (layer>new>null), name it 'sphere control' (or anything that makes sense to you) and add a slider control effect (effects>expression controls). if you want you can name it too, select the effect, hit enter/return and type 'radius control' or something like that. and give it a starting value like 200.
select the null in the timeline and hit 'uu' to reveal the only property that has been modified, the slider value.
now select the earth sphere.. it's radius can have the same value as the slider control, so option-click (or alt-click) the stopwatch for radius to add an expression. then use the expression pickwhip for radius and drag it to the slider control value in the timeline. this will write an expression that links the radius to the slider value. if you want you can drag the slider value and the sphere radius will change too.
now that you have an expression for one sphere, you can apply it to the others. select the radius property taht has the expression and choose edit>copy expression only. then select the other sphere layers and choose edit>paste. now the all linked to the slider but have the exact same radius.
to fix that, with the sphere layers selected, hit 'ee' to reveal the expressions for those layers.
for the cloud radius just add * 1.01 to the end of the expression. you're just telling ae to multiply the value of the slider by 1.02 for this radius' value.
for the atmosphere, add * 1.02 to it's radius expression.
now as you adjust the slider, it should control all the radii.
you could also use an expression to link the offset values to a point control, or to the null layer's position directly. you could even link the light controls, to be able to change the lighting off all the sphere's at once.
you can spend a lot of time setting this up and linking everything together, but as dave pointed out, if you know what you want first, you can probably set this up faster without expressions... so planning is often the best way to save time. but if you know that you will get art direction from somebody, use of expressions can make it easier to make changes.
KCPQ, KMYQ & KRCW
Thanks! I was not sure my animation would work out the first time, so that's why I wanted to use an expression, linking all of the spheres togeather. So that when I need to change something, I only need to animate the slider control again. Kevins tip worked for me, and I managed to make a really smooth tilting and zooming animation while the whole Earth rotates to the place I want. By the way, I used this method to set up all the rotation controls aswell.