Depends which market you are in. First for a ray tracer to be effective it must model billions of photons, so optimising how and where you fire them is key to

Depends which market you are in. First for a ray tracer to be effective it must model billions of photons, so optimising how and where you fire them is key to making a _fast_ ray tracer. A non optimised, (therefore multi hour per single image render time) ray tracer is fairly easy to write (can be done in less than 5k lines of code) As for what the point is, there are a number of things: Raytracing means that you are effectively simulating the physical properties of something. This means that light interactions between objects come for free (well, kinda) When you put a lamp shade on a light bulb, it will cast shadows. Windows are transparent, etc, etc. In raster land, thats not a given. This means that architects who are designing building in cad, and have been very specific with their material choices can get accurate representations of how the light will interact inside the building. Maxwell render bills it's self as a physically accurate renderer, but it is _slow_, very pretty, but slow. (yes, there are trade-offs, a real-time renderer is not going to be physically accurate, but it is way more accurate than a rasterer) So making small incremental changes might mean waiting for a number of hours for the render to finish. In VFX, renders can take > 24 hours per layer, per frame (Each finished frame might have > 1000 assets, each with > 100 versions, each with a number of layers.) So any time saving there can save thousands. Also, getting real time feedback makes production much more fluid and intuitive. At the moment, when acting with CGI characters or backgrounds, you have to use a standin: https://imgur.com/gallery/OVk4DYp https://imgur.com/gallery/OVk4DYp This means that the cameras have to be much more scripted, a lot of working out has to be done to make sure that CGI elements blend in properly. In the film gravity, they used realtime motion capture heavily, as most of the elements (in some case only the eyes of the actors are real) are CGI. The director is a visual person and wanted to look through a camera and see the space station. He would have sacrificed his left testicle to get the demo's level of realism in his view piece