PowerVR GR6500: Ray tracing is the future and the future is now

Ray tracing works backwards from the way actual optics works. It sends out a ray for each pixel and then finds out what it falls on then does math to figure out what it should look like. In a simple example, you have a few light sources and you trace a ray back to an object (polygonal surface), then you shoot off other rays from there toward the light sources (or you shoot off potential reverse reflection rays). If something is blocking a light source you adjust the amount of shadow being rendered or you bounce off of that surface again toward the light sources, and so on. Making it possible to render shadows, reflections, and so on with decent fidelity.

In contrast to that technique you have "radiosity", where the illumination at each point on a surface is calculated based on its environment. Radiosity is better at rendering diffuse light, ray tracing is better at rendering reflected light.

The underlying difficulty is that illumination is a maddeningly combinatorial problem. In principle every part of every object in a scene contributes illumation to every part of every other object. The light falling on a desk lamp from the LEDs of a clock also illuminates the desk itself, and so on. Radiosity and ray tracing attempt to solve those problems by making simplifying assumptions and performing a subset of the calculations necessary to illuminate and render a scene completely faithfully. In principle a more proper ray tracing algorithm would be to send out a huge number of rays in every direction for every image field ray, then follow each of those through their evolution, sending out yet more for surfaces each fall on, and so on. But that's far too computationally intensive (it's an O(n!) level problem).

Path tracing is similar to these techniques but makes different simplifying assumptions. And the most important aspect is that instead of deterministically calculating everything in a specific way it uses a monte-carlo method of statistically sampling different "paths" then using the data to estimate the resulting illumination/image rendering. Path tracing results in a compromise between ray tracing and radiosity of being able to render both reflective and diffuse light well, though it has its own short-comings.

I don't think it _is_ super obvious. Rather, I think the goal is to properly fill in the scene with the very subtle clues we unconsciously look for.

I had a similar experience working a bit with Radiance years ago. The output looked mediocre, at best, but it was reporting a real view of the scene; it's call to fame is that it outputs real energy values in physical units (like energy per unit solid angle or luminance or such). But despite the cartoony models I provided, it did demonstrate subtleties that weren't hacks (needed for this application), things that you wouldn't think to or bother implementing directly.

This? This grabs a lot of needed visual artifacts faster and more correctly without crazy hacks (or so it seems - it does say hybrid rendering).

I'm sorry man, but that sounds crazy. Raytraced scenes are much easier for artists to control the results because things actually behave like you would intuitively expect (if the amount of rays is high enough).

If raytraced scenes were hard to control, why would every single animated movie be raytraced?

Raytracing really is the be all and end all of graphics. The more rays you can render, the more realistic your scene will be, up to 100% realism.

Of course, we can come pretty far with the hacks as well, and it's hard to say if hardware raytracing can come close to the quality hardware shader hacks can achieve on traditional GPU's in real time.

They'd have to either sacrifice yield or sacrifice FP32 units.

Also, if they put FP64 support in their gaming cards they wouldn't be able to charge scientists and engineers extra.

They should have showed the car moving. You'd have seen the reflection slide up the hood in the raytraced demo.

It takes A LOT of work and planning to get light and shadow correct in a raster setting. Most AAA games don't bother. Raytracing makes it easy to get them right, which will make all the difference in the world.