Hundreds of isometric characters walking around !

[Dan Ebberts]

>Can you use expressions to detect what direction a layer is traveling and then switch its precomp animation to match that?

In general, yes. If you’re generating the movement by animating the position property, for example, you can look at the position property’s velocity and determine which quadrant the direction of the movement is in by the sign of the x and y components: upper right (+, -), lower right (+, +), lower left (-, +) or upper left (-, -). That could be used to determine which section of a time remapped walk cycle plays (or which layer in a pre-comp is visible). Definitely do-able, with a number of options.

[Matt Jones]

That’s encouraging!

I’ll share what I’ve got, it kind of works… so far at least.

The best I can get (with help from a robot friend and a sledge hammer) is below.
I’ve gone for 8 directions of walking.

So, on my character layer there’s a slider Slider effect called ‘Direction’ with this expression

// Store the current position
var currentPosition = position.value;
// Store the previous position
var previousPosition = position.valueAtTime(time - thisComp.frameDuration);
// Calculate the difference in position to determine the direction
var deltaX = currentPosition[0] - previousPosition[0];
var deltaY = currentPosition[1] - previousPosition[1];
var directionNumber = 0;
if (deltaX == 0 && deltaY == 0) {
    directionNumber = 0; // No movement
} else {
    var angle = Math.atan2(deltaY, deltaX) * 180 / Math.PI;
    if (angle >= -22.5 && angle < 22.5) {
        directionNumber = 4; // Right
    } else if (angle >= 22.5 && angle < 67.5) {
        directionNumber = 8; // Down-Right
    } else if (angle >= 67.5 && angle < 112.5) {
        directionNumber = 2; // Down
    } else if (angle >= 112.5 && angle < 157.5) {
        directionNumber = 7; // Down-Left
    } else if (angle >= -67.5 && angle < -22.5) {
        directionNumber = 6; // Up-Right
    } else if (angle >= -112.5 && angle < -67.5) {
        directionNumber = 1; // Up
    } else if (angle >= -157.5 && angle < -112.5) {
        directionNumber = 5; // Up-Left
    } else {
        directionNumber = 3; // Left
    }
}
// Return the current position to avoid breaking the position expression
currentPosition;
// You can see the direction number in the slider
directionNumber;

and then in time remap

// Get the direction number from the Direction slider control
var directionNumber = effect("Direction")("Slider").value;
// Map the direction number to specific times
// Adjust these values based on your precomp timing
var timeMap = [0, 1, 2, 3, 4, 5, 6, 7, 8]; // Example times for each direction
// Return the corresponding time remap value
timeMap[Math.round(directionNumber)];

the time remap doesn’t give those numbers but its predictably wrong which is good enough, I guess !

[Dan Ebberts]

I think you’re on the right track, except that the time remapping part has to figure out how long the animation has been moving in the current direction. I haven’t tested any of this (so there may be typos), but here’s how I’d do the slider:

v = position.velocity;
if (v[0] == 0 && v[1] == 0){
  n = 0;
}else{
  a = radiansToDegrees(Math.atan2(v[1],v[0])) + 180;
  if (a < 22.5){
    n = 3;
  }else if (a < 67.5){
    n = 5;
  }else if (a < 112.5){
    n = 1;
  }else if (a < 157.5){
    n = 6;
  }else if (a < 202.5){
    n = 4;
  }else if (a < 247.5){
    n = 8;
  }else if (a < 292.5){
    n = 2;
  }else if (a < 337.5){
    n = 7;
  }else{
    n = 3;
  }
}
n

And here’s an attempt at the time remapping:

s = effect("Direction")("Slider");
timeMap = [0, 1, 2, 3, 4, 5, 6, 7, 8];
n = Math.round(s.value);
f = timeToFrames(time-thisComp.frameDuration);
while (f >= 0 ){
  nPrev = s.valueAtTime(framesToTime(f));
  if (nPrev != n) break;
  f--;
}
t = time - framesToTime(f+1);
timeMap[n] + t;