Ok, this is a very simple example. A proper solution for stained glass is going to need more work, but this at least demonstrates the use of the Kt parameter.

This is a simple plane stood vertically in front of Woody (so that I can see that it is indeed see-through). Light is from a single spot light behind the plane, pointing at the sphere. You can see that the coloured pattern on the plane is colouring the light from the spot light, colouring the ground and the sphere.

Obviously this isn't very realistic at all - it's just a simple demo to show 'transmission' working.

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