Hi everyone,

I’m trying to create an interactive lighting setup in Houdini using Karma and would appreciate some guidance.

I have a floor made up of multiple individual boxes, all illuminated with the same white-colored light. A ball is bouncing across the floor, and I want the lighting or color of each box to change to blue whenever the ball makes contact with it.

Ideally, the effect would work dynamically: (https://www.youtube.com/watch?v=NuGATtVlXAU)

* All boxes start with white lighting.
* When the ball touches a specific box, that box changes to blue.
* When the ball moves away, the box returns to white (optionally with a smooth transition).
* The setup should work with Karma rendering, preferably in Solaris/USD.

What would be the recommended approach for detecting the contact and driving the color of the corresponding light or emissive material?

Any example node setups or guidance would be greatly appreciated. Thanks!