LightPositionTool as a node

[Riccardo Cecchinato]

Hello dear Gaffer devs!

In Gaffer 1.6.6.1 I was wondering if there is a way to obtain the LightPositionTool behavior as a node.

An use case example:

using a locator on a surface to "aim" my spotlight reflection around that locator position all the time.

Thank you in advance for your always unvaluable help!

Riccardo

[John Haddon]

Hi Riccardo,

I like the idea of a ReflectionConstraint node - feel free to open an issue for that on GitHub.

In the meantime, I've attached a simple little setup that achieves the same using an expression and a couple of transform queries. Probably needs refining to be useful, but hopefully gives you a good starting point.

Cheers...

John

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[Riccardo Cecchinato]

Hello John!

More than happy to open an issue on GitHub but I never did it before, may I ask you any quick link and/or documentation that explains how to do so?

I started playing around with your network (thank you!!), trying to implement it on an eye_rig node I developed last year.

I guess "locking" a spotlight reflection over a specific part of a spherical mesh is a pretty specific use case, since I am not obtaining visual results for the moment (but the spotlights are positioning is a somewhat logical way).

I'll keep you posted on the advancements and open the issue as soon as I understand how to do it properly!

Thanks a million,

Riccardo

[Riccardo Cecchinato]

Hello John!

After having extracted the normal of my geometry target, I managed to successfully implement your node to my eye rig. Very exciting to see the placement fully automatized thanks to your math and the incoming animation rig!

Lots of possibilities and ways to improve the system to make it less "fake", but considering it is already based on physical lights, it's already a great starting point.

As usual, thanks a million for your always punctual help. Still eager to open the GitHub issue as soon as I understand how to do it in the proper way!

Best,

Riccardo

[John Haddon]

On Wed, Mar 11, 2026 at 11:17 AM Riccardo Cecchinato <rcecc...@stimstudio.com> wrote:

After having extracted the normal of my geometry target, I managed to successfully implement your node to my eye rig. Very exciting to see the placement fully automatized thanks to your math and the incoming animation rig!

That's great! Glad you got it working...

Cheers...

John