Working emissive materials in RTGI (with screenshots)

@TommyBear Hey, thanks for your help the other day! I got this up and running and it produced the best results out of Unreal Engine’s DXR implementation that I’ve seen to date, with the only noise in the scene being the direct result of the Engine’s work-in-progress denoiser. I have no idea the real reason behind Epic’s denial of your pull request (I found their explanation unconvincing) but I hope they get back to you with better clarity than we saw in the comment.

We’re all rooting for you! Great work!