What Room Is This?

Cybersox

ANGELREAPER1972 said:

think of hdri's as a green screen just like in movies or tv where greenscreens are used for actors or tv show hosts stand in front of and an image is projected on it

Except that Green Screens and other traveling matte and video keying systems simply replace the image behind the subject, so great care has to be taken with green screen photography to light the foreground element to match the lighting in the background element (traditionally called a "plate") so that the shadows and color balance all match.  By comparison, HDRs actually serve as both light sources and image sources from all angles, so not only do they alter the levels and colors of the illumination on the subject to match with the background, but they also can be seen reflected on refective parts of the foreground subjects.  A better analogy is the immersive video rooms being used now on shows like the Mandalorian, where the subject is surrounded on all sides by LED screens so that the video screens act to both provide a background image and serve as a light source.