How can I apply the position expressions in after effects?

Question

I am new in this expressions and scripting. I want a circular shape layer to move in a projectile path following actual physics formula.

Dan Ebberts · Accepted Answer

Just using the basic projectile formula, you could do something like this:

g = -55000;
angle = -45;
v0 = 10000;

a = degreesToRadians(angle);
vx = v0*Math.cos(a)*time;
vy = v0*Math.sin(a)*time - g*time*time/2;
value + [vx,vy]

Adjust gravity (g), initial velocity (v0), and launch angle (angle) to get the result you want.

Mylenium · Answer

You need to be much more specific. No offense, but this is one of those "What does it have to do with anything?" questions. Inside AE physical units don't matter, only pixels. And that being the case, all you are ever going to get out of your calculations are pixel values. Sure, correlating them to physical units by ways of a DPI setting vs. actual physical screen size, but even then measuring your AE comp on screen at crooked zoom levels and without considering the operating system's/ graphic's driver's own DPI calculations is perhaps not that terribly useful. Similarly, the physical velocity would need to be relative to the actual framerate as that's simply how film/ video works and you haven't offered any of this info. Again, I don't mean to be rude, but you need to be much more specific. There's a ton of things to consider here. If you need this e.g. for a large projection and it needs to be reasonably accurate to realworld dimensions, all these details matter. If it is for an explainer video or something, then this may be a whole different story and none of this may even be relevant, as you could simply lable it whatever you want. so for what it's worth, you need to explain what you need this actually for and then we can take it from there. Other than that you can always find some info on how to calculate a ballistic trajectory based on projectile weight, gravity, air resistance and possibly other factors. In fact there may still be that old, old "Tank" game AE project out there that someoen created when expressions were new in version 5 15 years or so ago. You would not be able to open it in a current AE, but since it was a tutorial you could at least learn something from the code bits.

Mylenium

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