Ray traced rectangle lights with animated textures - how?

[Suthriel]

@shokomon

You mention that Porsche used a Media Player as a texture (not a light function). But when I do that my nice soft area light just turns into a movie projector. This problem is demonstrated very clearly in your own result video. Your rectangle light is somehow magically projecting a perfectly legible image of peoples faces etc onto the floor - like a projector. A real TV screen has no lens in front of it, and therefore it just makes a soft blob of coloured light (which the tutorial creates with blur filters, light functions, 3x the needed number of lights etc). I’m lighting my scene with multiple giant video walls, so the difference is huge.

Ok, that blurry lighting… dunno ^.^ But if you look at this clip here, were they show an interactive demo with the used lights, then you can see, that their floor is quite reflective/metallic, and does reflect a pretty clear and sharp image of the background TV and the car itself (1 minute mark) :

“The Speed of Light” Porsche 911 Speedster Concept + Interactive Demo | Unreal Engine

Maybe the pdf contains some hint, because those boxes, they are moving, seem to be a combination of rectangular light and an emissive plane. Take a look at page 56, where one of those boxes is marked, and what it contains. BP_LightFree contains a RectLight and a Plane.

PDF: http://on-demand.gputechconf.com/gtc…pdf/CH8807.pdf

Have tested it with an emissive plane instead of a rect light, and maybe with a better GPU and more samples and more bounces for reflection and Global Illumination, it could look closer to your desired TV screen:

Unreal Engine - Car and TV Test

Edit: The only other way i can think of, would be to create a blurry video copy, that you use for the rect light, and the normal sharp video for the emissive plane for the reflections.