Control Rig: Draw Line node drawing 2 lines instead of 1

Development Character & Animation
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1

I have a simple FK control rig for my character’s eyes.

I want to be able to draw a line from the eye out in the direction the character is looking, along the forward vector.

I am using 4.27, so don’t have access to the Matrix math in UE5.

Currently I have a variable “Forward” (0, 0, 1), that I rotate per the rotation of the control and then put that into the Draw Line node (see attached picture).

However, this is drawing 2 lines rather than 1.

One line is correct and moves with the forward/eyeline direction when I rotate the eye/control.

The second, incorrect line moves with the rotation but at the fraction of the correct angle.

I have previously successfully used the Draw Line node with an Aim set up (bone aiming at the control). But understand this is a different situation with the Control directly setting the transform of the Bone it is parented to in the rig hierarchy.

How would I fix this so I only get the 1 correct line firing out from the eye’s forward vector?

IMG_9606
IMG_96061920×1440 299 KB

2

Follow up to this.

The Draw node here worked correctly (with one line) when the control was not parented to the bone (ie at the bottom of the rig heirarchy. So then I tried setting the initial transform of this control to the bone during the setup event.

In sequencer, my characters already have an animation track applied and I am using the control rig as an additive adjustment to the anim track. These anim tracks don’t have root motion, so the draw feature works, but the non-parented control moves to be relative to the pivot, which is no good.

I ended up with a hacky solution, creating the line draw by adding an additional control parented to the original control and scaling an gizmo so it essentially became the line draw.