Understanding the Driving Curve in the Bone Driven Controller node

Development Programming & Scripting
1

Hello everyone. I`m quite new to UE4 and blueprints, so please forgive me if I make some obvious mistakes here.

Im trying to understand how the Driving Curve is mapped to both the incoming and outgoing values in this node, because Im having a hard time noticing the effect it has (whereas the multiplier value is very obvious).

I have a bone that rotates on one axis depending on the rotations of its parent. Ive set it up so Im reading the correct rotation axis, and driving the correct target rotation axis. I created a Curve in the Content Browser, and selected it in the node to be used as the driving curve.
To get started, I created three keyframes in the curve. One at t=0, with a value of 0, one at t=-90 with a value of 90, and one with t=90 with a value of 90. My reasoning was that since Im generating an angle from an angle, rotating the driving bone by 90 degrees would rotate my driven bone by 90 degrees. Likewise, rotating the driving bone by -90 degrees also would rotate my driven bone by 90 degrees. However, thats not what Im seeing. I hardly see any effect on the driven bone. Ive tried different values on my keyframes, but can’t seem to get an effect I’d be able to understand clearly.
So, I guess I will have two questions at this point…

  1. How does the Time (x-axis) on the curve relate to the driving transform axis in this node? Is it a 1-1 relationship? (i.e. 1 sec = 1 degree, in my case).

  2. Does the node perform internal conversions when the transforms are not equivalent? Say, driving the Y translation axis with an X-axis rotation. Does the node perform an internal degrees to radians conversion?

Any help understanding how to use these curves will be greatly appreciated. The reason I decided to explore their use (instead of just relying on the multiplier) is because I have a few bones in my character that need to be driven by a given amount when the driving rotations is positive, and by a different amount when it is negative. I thought the curve would handle that just fine.

Thanks in advance!

2

Well, I’ve spent some time playing with this, and the more I play with it, the more I see that this curve is not really a curve that drives output values in function to input values. This just seems to be a multiplier curve, which means I won’t be able to use it for my purposes because I need to change the direction of rotation of the driven bone based on the direction of rotation of the driving bone, and this curve doesn’t seem differentiate incoming values. I’ve tried a bunch of stuff, and it seems only one side of the graph does anything. It’s as if the operation was wrapped in an ABS function.

Anyway, looks like a dead end to me, unless I’m really missing something. If anyone has any pointers, I’d be happy to hear about them. Otherwise, I’ll explore other options. Cheers!