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# Adding tracer lines on an object with vectors?

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 Adding tracer lines on an object with vectors? on Sep 29, 2014 at 8:16:37 am

is this possible? I havent even tried it just thinking of ideas- looking for something like C4D's tracer effector, with speed lines relative to the speed of the object. I was thinking maybe Beam effect with some vector math functions? I've never actually used vectors in AE so I got scared and came here

 Re: Adding tracer lines on an object with vectors?on Sep 29, 2014 at 5:05:03 pm

Vector math needn't be THAT scary...

Can you make a mockup of how you want you speed lines to work?

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]

 Re: Adding tracer lines on an object with vectors?on Sep 29, 2014 at 7:02:28 pm

Sure, here's a demoo, super simple. Thanks :)

8051_speedlinedemo1.mp4.zip

 Re: Adding tracer lines on an object with vectors?on Sep 29, 2014 at 10:15:33 pm

Will they always move one way along a straight line like this?

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]

 Re: Adding tracer lines on an object with vectors?on Sep 30, 2014 at 2:12:09 am

Just one direction for this project, yes

 Re: Adding tracer lines on an object with vectors?on Sep 30, 2014 at 9:40:13 am

I would draw the speed lines in a group on a shape layer, add Trim Paths, and use an expression like this for the End property:

```maximumSpeedRange = 250; s = length(sub(position,position.valueAtTime(time-thisComp.frameDuration))); ease(s,0,maximumSpeedRange,0,100)```

s in this expression is the magnitude of the difference between the layer's current position and its position on the frame before.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]

 Re: Adding tracer lines on an object with vectors?on Sep 30, 2014 at 5:47:08 pm

Ok cool, now if I need them to change directions how would you go about that? When I said one direction I meant one at a time. ie) it moves left then pauses, then moves up and pauses, etc.

 Re: Adding tracer lines on an object with vectors?on Oct 3, 2014 at 9:53:40 am

[Ryan Paterson] "Ok cool, now if I need them to change directions how would you go about that? When I said one direction I meant one at a time. ie) it moves left then pauses, then moves up and pauses, etc."

If you put the lines on a separate shape layer, offset them from the center, and parent the tracer line shape layer to the moving object you could rotate the shape layer according to the direction of movement.

Change the end paths expression to this:
```maximumSpeedRange = 8; p1 = toWorld(thisLayer.transform.anchorPoint); p2 = toWorld(thisLayer.transform.anchorPoint,time-thisComp.frameDuration); s = length(p2-p1); ease(s,0,maximumSpeedRange,0,100)```

And add a rotation expression like this:
```p1 = toWorld(thisLayer.transform.anchorPoint); p2 = toWorld(thisLayer.transform.anchorPoint,time-thisComp.frameDuration); delta = p2 - p1; radiansToDegrees(Math.atan2(delta[1],delta[0]));```

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]