Making a glass object glow in a colour that it isn't

Hi! I’m totally really new to blender and figuring things out as I go along, with a vision of a scene I want to make in mind. I’m afraid I don’t know much of the terminology, but I can look things up. I only ask this here because I haven’t found a solution elsewhere.

That said, I want to make this icosahedron glow in any colour except green, which is the colour of the glass that the surface is. I know that in terms of physics, it’s not strictly possible to send coloured light through a filter that isn’t that colour… But it feels like it’s possible here.

I put a sphere with the emission shader inside the icosahedron, because I want it to look like it’s glowing from inside instead of just being an object that emits light. However, the sphere inside isn’t even visible when rendered, no matter which ways I change the glass (admittedly I didn’t try every option, but everything that occurred to me. There’s too many to trial and error in blender I find.)

Does anyone know what I can do to make this look like it has a light coming from within, that isn’t necessarily green?

Shiny Rock.blend (687.3 KB)

Just be aware - lighting a scene using an emitter inside a refractive object will be very noisy - as you are essentially lighting the scene using caustics.

That said - what you are after is possible with a bit of light path trickery.

I have two spheres in this scene. A large green glass one and a smaller one inside it with a red emitter material.

These screenshots show the material nodes for the two spheres.

Thank you @moony! If there’s a better way to do a similar thing, I would obviously prefer to do that. But I just set the samples / clamping way high and it gets rid of the bits mostly.

I fiddled some more with the settings and got the intended effect, so thanks :slight_smile:

For anyone looking at the thread in the future, by fiddling with some extra mix shaders, you can also do the following: