How to use Look At Node in AnimBP without rolling the bone

Development Character & Animation
, , , , ,
1

Hi Everyone,

There’s a very useful node in AnimBP called “Look At” that can be used to orient a bone so that it can point to a specific direction. I’m currently using it with the default UE4 Mannequin. So you can follow along if you want to.

It works perfectly when I ignore the up axis. I use it to rotate the thigh_l bone to any direction I want. I went inside the mannequin skeleton and found that the thigh_l bone has the y axis component (the negative side of the axis) aligned with it’s forward axis. So I used that as my look at axis by entering : 0 -1 0.

Everything was running perfect. But I noticed that some rotations cause the thigh bone to rotate around itself (roll axis). I dont want that. I want to orient the bone towards a direction while maintaining it’s default roll rotation.

So I tried using the up axis this time inside the Look At Node. But any axis I use, I get weird results. I tried local axis and world axis and they both lead to really weird results. Basically, they all stop the look at node from pointing to the correct direction.

But if I dont use the up axis, the thigh bone rolls when I use the look at node. What am I missing? Is there a way I can use the look at node while keeping the default roll rotation.

1 Like
2

Hi. I know its been a few years, but did u find it out later? I have the same problem.

3

There isn’t one.

Animation blueprint arent supposed to have any code.

The character needs to process whatever, however, and then that information in the form of whatever (here a vector) is passed onto the ABP.

Anything at all that involves any coding or parsing should never be a part of an animation blueprint.
So, the look at node is an immidiate nono.

Even if all you are doing is copying info from one bone to another - which a copy node will do just the same, and without any processing behind it - you are still in the this is trash territory.

Depending on what goal you are trying to achieve, adding in a leg IK or a CCKD or a Fabrik node with the final direction/relevant info - probably including a rotation - passed into it, will likely work a lot better. And also follow best paractice…