I need help with this Expression: linear(time, 0, thisComp.duration, 0, 100);

[Stephen Dixon]

the distance around a rectangle is the (width + height) * 2. The proportion of the distance to the first vertex is (pseudocode):

(the distance from start to point 1)/total distance

and to the third point

(the distance from start to pt 1 + distance from pt 1 to pt 2)/total distance

if the rectangle goes clockwise from the top left the first distance is equal to the width, so to stop at the first vertex we multiply the expression you had by

width / ((width + height) * 2)

or for the whole thing

let w = <link to="" the="" shape's="" width,="" use="" pick-whip="">;
let h = <link to="" the="" shape's="" height,="" use="" pick-whip="">;
let prop = w / ((w + h) * 2); // proportion of distance
linear(time, 0, thisComp.duration, 0, 100) / prop;

for the second point the proportion is going to be

(width + height) /((width + height)*2)

There’s no need to do anything complicated here, this will always equate to 1/2. so dividing your original expression by 2 should work here. The third point is going to be

(width * 2 + height) /((width + height)*2)

so the expression will be

let w = <link to="" the="" shape's="" width,="" use="" pick-whip="">;
let h = <link to="" the="" shape's="" height,="" use="" pick-whip="">;
let prop = (w * 2 + h)/ ((w + h) * 2); // proportion of distance
linear(time, 0, thisComp.duration, 0, 100) / prop;

To go anti-clockwise swap w for h on the top of the fraction, e.g. for the third point:

let w = <link to="" the="" shape's="" width,="" use="" pick-whip="">;
let h = <link to="" the="" shape's="" height,="" use="" pick-whip="">;
let prop = (h * 2 + w)/ ((w + h) * 2); // h * 2 + w instead of w * 2 + h
linear(time, 0, thisComp.duration, 0, 100) / prop;

[Nick Mara]

Hi Stephen,

Thanks for your kind help !!!

I’ve tried one of the expression you provided me and I think I’m doing something wrong.

Here is a short video to show you what I did:

https://www.youtube.com/watch?v=mBq1Ce8946M

Could you please tell me what is wrong?

I need to tell you another thing:

This is part of a project where for necessity, the Shape Layer Path it’s converted to a Bezier Path which auto-resize itself due to the composition size via this expression:

cW = thisComp.width;
cH = thisComp.height;
corners = [[-cW/2,-cH/2], [-cW/2,cH/2],[cW/2,cH/2],[cW/2,-cH/2]];
startCorner = 2; // Link to Slider Control
p1 = corners.splice(0,startCorner-1);
corners = corners.concat(p1);
createPath(corners)

You can also change the start point of the path using a slider control.

I’m telling you this because, as you know for sure, when you convert the Shape Layer Path to a Bezier Path, you don’t have direct access to the Width and Height properties anymore.

Is there another expression or a workaround to solve this problem always keeping in mind that I need to use also this expression on the “End” property of the Trim Path:

linear(time, 0, thisComp.duration, 0, 100);

THANKS IN ADVANCE !!!

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[Andrei Popa]

And this to the End property of your trim paths. You have to also add a slider control named Stop Point in which you write at which point you want it to stop. In the shortPoints = [1, 4]; I wrote the point which start a height line.

function arrIncludes(arr, element) {
    for (var i = 0; i < arr.length; i++) {
        if (element == arr[i]) return true
    }
    return false;
}
L = thisComp.width;
l = thisComp.height;
percentL = 50 * L / (L + l);
percentl = 50 * l / (L + l);
beginPoint = effect("Slider Control")("Slider").value;
stopPoint = effect("Stop Point")("Slider") % 4;
shortPoints = [1, 4];
firstLInstances = Math.ceil(stopPoint / 2);
if (arrIncludes(shortPoints, beginPoint)) {
    theEnd = percentl * firstLInstances + percentL * (stopPoint - firstLInstances);
} else {
    theEnd = percentL * firstLInstances + percentl * (stopPoint - firstLInstances);
}
theEnd = theEnd == 0 ? 100 : theEnd;
linear(time, 0, thisComp.duration, 0, theEnd)

[Nick Mara]

Hey Andrei,

Thanks for your response, sorry for splitting the discussion in two parts, my fault.

Let’s try to stay on this one:

https://creativecow.net/forums/thread/self-resize-a-bezier-path-shape-layer-to-comp-size-and-more/#post-2336076

Thanks a bunch

Self – Resize a Bezier Path Shape Layer to Comp size and more