Hi Bobby,
TG4 Beta can render coloured shadows, but it has to be set up in a particular way. In future I'd like to make this easier to do. But for now, here's some stuff from the change log:
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Partial-opacity shadows. The renderer can now render partially-opaque shadows of non-displaceable objects. Partial opacity is achieved with the Default Shader by using opacity less than 1 or using an opacity texture or opacity functon (many vegetation models already do this, with partial opacity occurring on anti-aliased edges in the texture).
It's not just greyscale, but colour too. If you use a colour for opacity, it will produce coloured shadows. It may not be intuitive because the shadow colour will be the complementary colour of the opacity. However, since you're using an image texture you can enable "invert opacity image" and then the colour in the texture will be the colour of the transparency.
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For now, this only works for shadows, while opacity visible to the camera still works as before: it can only be either 0 or 1 and each pixel will jump to whichever value is closest. The RTP has an extra capability that's not in the main render: the RTP can render these partial opacities visible to the camera as well, but we'll change this in future to match the capabilities of the main renderer.
Hopefully that's self-explanatory.
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Please note: Partial opacity is not the same as refractive transparency in the Glass Shader and Water Shader. If you want to use this new feature to render semi-transparent shadows of glass-like objects, we recommend that you use a separate INVISIBLE object for casting shadows with reduced opacity, while keeping the visible object fully opaque (opacity 1) with shadows turned off. This will avoid surprises in future versions of Terragen that can render partial opacity visible to the camera.
This affects how you're going to use it to do stained glass windows. I'd recommend that you have two copies of the glass parts. One copy will use the same setup you have now to tint the world outside, but has shadows turned OFF. Then you'll need another copy that is INVISIBLE to camera but has shadows turned ON, and uses a Default Shader with an opacity texture to control the colour of the shadows.
Yes, this is more complicated than it should be. I'd like to make this straightforward in future.
How are you doing the coloured transparency, by the way?
Matt