From Rasterization to Full Real-Time Path Tracing: The Evolution of Graphical Rendering Techniques

Video game artists have become highly capable at pushing the limits of rasterization, but it remains a complicated, time-consuming process, ubiquitous only because it’s computationally cheap. There are some challenges that simply can’t be overcome through sophisticated work-arounds.

“The problem here is that most lighting interactions are not local. Most interesting lighting interactions turn out to require knowledge of the scene around you,” explains NVIDIA’s Nuno Subtil. “With rasterization, this is really difficult. All the information you get to compute your color ends up being determined by whatever you can attach to the three vertices of the triangle; either directly, via interpolation, or indirectly, via some sort of texture map lookups.”

In the first image, there is no drape in front of the off-screen window, allowing for sharp, physically correct shafts of light to accent the room. In the second image, a drape has been placed in front of the window, which heavily diffuses the light. This is easy to do with ray tracing, but very difficult to do with rasterization. 

To overcome the hurdles inherent in rasterization, NVIDIA has been leading the charge into ray-tracing, a movement that has required the introduction of new hardware. In the video below, Nuno explains the role that NVIDIA’s Turing architecture plays in delivering real-time ray traced games to consumers. He details the evolution of graphical rendering, ending with an explanation of full real-time path tracing: the “holy grail” of rendering solutions.

This video is an excerpt from a full forty minute GDC 19 talk, entitled Ray Tracing in Vulkan. That talk can be viewed here. The full discussion explores NVIDIA’s API for exposing RTX through Vulkan. Nuno discusses how ray tracing fits in with a low-level rasterization API and covers details about NVIDIA’s Vulkan ray tracing extension.

If you are working on ray-traced games, we also recommend looking at our newly released Nsight Graphics 2019.3, a debugging and GPU profiling tool which has been updated to include support for DXR and NVIDIA VKRay.