Thanks Dan this is the answer I was looking for - I think one thing that was confusing me was that I was thinking in/outTangents were actual points rather than relative point so I was looking to find the real x,y point rather than how they related to the point like a parent/child relationship. Hope I got that correct, thanks for clearing this up and for the actual math.

Tim T

On May 21, 2018 at 12:54 PM Dan Ebberts <AE-List@media-motion.tv> wrote:

Just from looking at how AE does it, the math doesn’t seem all that complex. For all the points except the first and last, it looks like you just subtract the previous point from the next point and divide that vector by 6 to get the out tangent of the current point. Then invert that for the in tangent.

 

If the path is closed, for the first and last point you wrap around. So, for the first point you would subtract the last point from the 2^nd point, divide by 6, etc.

 

If the path is open, for the first point you would subtract the first point from the second point and divide by 6 for the out tangent and use [0,0] for the in tangent.

 

Do something similar for the last point.

 

 

Dan

 

From: After Effects Mail List <AE-List@media-motion.tv>
Sent: Monday, May 21, 2018 11:02 AM
To: After Effects Mail List <AE-List@media-motion.tv>
Subject: Re: [AE] inTangents/outTangents Math

 

Thanks Chris - there is a ton of info on the web about bezier curves and I am getting what the behind the scenes mechanism is doing - but maybe my real question is if I create a spline via a script I want to know how to calculate the in and out tangents to make a spline that mimics the auto bezier path. Is that even possible?

 

Thanks

Tim T

On May 20, 2018 at 1:22 AM Chris Zwar <AE-List@media-motion.tv> wrote:

Here’s a starting point.

 

http://jamie-wong.com/post/bezier-curves/

 

On 20 May 2018, at 2:39 pm, TIM THIESSEN <AE-List@media-motion.tv> wrote:

 

Can any one direct me to where I can read about calculating the inTangent/outTangents of a path - I want to build a curved path (like auto bezier) but I don't know the math to figure out the in/out Tangents.

 

Thank

Tim T