Re:A Ray-Tracing Pioneer Explains How He Stumbled into Globa...
by dahart on Friday August 03, 2018 @09:54AM
(#17679839)
Path tracing doesn't exist without ray tracing. Tracing a ray is one part of tracing a path, because a path is a connected chain of ray segments.
"Whitted ray tracing" or "recursive ray tracing" are sometimes used to refer to a complete renderer or complete shading technique used in the 80s that is not global illumination. That sounds like what you're thinking of. But that's not today's meaning of ray tracing. "Ray tracing" can (and these days normally does) refer to a visibility primitive that is used in many different kinds of renderers, and that's what NVIDIA is promoting, that's what graphics people mean by "ray tracing" these days.
> ray tracing is largely an obsolete method
Recursive ray tracing as a rendering technique might be out of fashion, but tracing rays is far from obsolete. Exactly the opposite, it's about to challenge rasterization.
> In fact ray tracing cannot do global illuminuation and any ray tracing engine that does that is essentially including a hack on top of its core ray tracer.
Not true at all. Path tracing is done using a ray tracing engine. There are several other popular techniques for GI on top of ray tracing engines as well, e.g., photon mapping. There aren't many GI renderers that don't use ray tracing these days. It's possible to avoid ray tracing, but not at all common in practice.
> I just realized, nVidia is promoting ray-tracing as the future of CG, and everything they're describing are actually qualities/features of path tracing and have nothing to do with ray tracing (except for this historical article). I'm seriously perplexed.
I think you're perplexed because you don't quite understand what "ray tracing" means. NVIDIA is promoting ray tracing as a visibility primitive that can replace rasterization. The implications of this are that 1) path tracing and other forms of global illumination using the GPU are now possible, 2) visibility queries & acceleration structures will have GPU support and can be done very fast. 3) We get things like instancing at a much lower cost than with rasterization. 4) Lots of ad-hoc special effects can be done in a simpler and more principled and complete way. I'm referring to, for example, screen space effects that games are using. AO, reflections, bounce lighting, shadows, etc. All these techniques are tricky and separate from each other. With ray tracing they can be unified. 5) Ray tracing queries can be used in games for all kinds of other things including collision detection, path planning, and audio.
"Whitted ray tracing" or "recursive ray tracing" are sometimes used to refer to a complete renderer or complete shading technique used in the 80s that is not global illumination. That sounds like what you're thinking of. But that's not today's meaning of ray tracing. "Ray tracing" can (and these days normally does) refer to a visibility primitive that is used in many different kinds of renderers, and that's what NVIDIA is promoting, that's what graphics people mean by "ray tracing" these days.
> ray tracing is largely an obsolete method
Recursive ray tracing as a rendering technique might be out of fashion, but tracing rays is far from obsolete. Exactly the opposite, it's about to challenge rasterization.
> In fact ray tracing cannot do global illuminuation and any ray tracing engine that does that is essentially including a hack on top of its core ray tracer.
Not true at all. Path tracing is done using a ray tracing engine. There are several other popular techniques for GI on top of ray tracing engines as well, e.g., photon mapping. There aren't many GI renderers that don't use ray tracing these days. It's possible to avoid ray tracing, but not at all common in practice.
> I just realized, nVidia is promoting ray-tracing as the future of CG, and everything they're describing are actually qualities/features of path tracing and have nothing to do with ray tracing (except for this historical article). I'm seriously perplexed.
I think you're perplexed because you don't quite understand what "ray tracing" means. NVIDIA is promoting ray tracing as a visibility primitive that can replace rasterization. The implications of this are that 1) path tracing and other forms of global illumination using the GPU are now possible, 2) visibility queries & acceleration structures will have GPU support and can be done very fast. 3) We get things like instancing at a much lower cost than with rasterization. 4) Lots of ad-hoc special effects can be done in a simpler and more principled and complete way. I'm referring to, for example, screen space effects that games are using. AO, reflections, bounce lighting, shadows, etc. All these techniques are tricky and separate from each other. With ray tracing they can be unified. 5) Ray tracing queries can be used in games for all kinds of other things including collision detection, path planning, and audio.