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Nvidia RTX ends with an X, X-Plane starts with one. Perfect match?

Nvidia announced their latest bitcoin graphics cards on August 20th at Gamescom this year. Among the usual increase in transistors, they also disappointed all crypto miners by adding a feature that cannot (yet) be used to calculate cryptographic hashes: Ray Tracing! Ray tracing has long been seen as somewhat of a holy grail of graphics rendering, because it’s much closer to replicating the real world than traditional rasterization and shading. However, doing ray tracing in real time has been close to impossible so far. But hey, Nvidia just announced their new RTX GPUs that can do it, so when is X-Plane going to get a fancy ray traced renderer? This and various other questions that have been asked by X-Plane users, as well as some myths, shall be answered! If you have a question that isn’t answered here, feel free to ask it in the comments.

What Nvidia has shown is absolutely impressive. Unfortunately, the fine print of all the marketing hype is that sadly it can’t just be thrown in without engineering effort. The first thing needed is actual RTX hardware, which no one at LR currently has. The second thing needed is a Vulkan-based app; we are getting there, but not in any way that would support RTX. (the whole goal of the Vulkan renderer is to not change the way the world looks, so we’ll first need a shipping production Vulkan renderer.) But then… well, it’s not entirely clear what it takes to actually write a ray traced renderer in all of its details. Nvidia has not yet published the specification for the Vulkan extension (VK_NV_raytracing), but they have published slides from presentations. One thing is very clear: you can’t just copy and paste five lines of Nvidia sample code and suddenly wake up in a ray traced world.

What Nvidia provides is the scaffolding necessary to describe a scene, as well as to provide new types of shaders that allow casting rays from point A to point B and then report back what they hit along the way. This is a huge amount of work that the hardware is providing here, but it’s not the promised “5 lines and you’ll have ray tracing in your application” that’s being promised. To adopt ray tracing you will have to write the whole ray tracer yourself, from scratch; the hardware just enables you to do so now. This is akin to implementing HDR or PBR: Shaders are the base requirement to implement both of these, but once you have shaders you still need to actually implement HDR or PBR on top of them. Another example is building a house and being provided a plot of land that can support it. Sure, it’s great, now you have a place to build your house, but you still have to come up with a blueprint, pick materials to use and then actually build the thing. Implementing ray tracing will take a great amount of engineering effort, nobody is throwing in awesome reflections with every purchase of one RTX2080Ti for free!

The other thing that’s not entirely clear is how well ray tracing will even perform in an environment like X-Plane! Worlds in X-Plane are huge and open, not small scenes from a shooter with tight spacing. Lot’s of rays are needed, and they have to travel quite far, potentially intersecting with large amounts of geometry. How good does the hardware and API scale up to these sizes? Only time will tell. That’s of course not to diminish Nvidias achievement here, it’s an incredible feat of technology in its own right and this is just the first generation!

The other thing worth mentioning is that ray tracing is not just something that Nvidia secretly cooked up in their basement for a decade. This is going to be an industry wide thing, with APIs that will work across vendors! Historically one vendor has come out with a fancy new way to do things which then became the standard adopted by other vendors. Nvidia has come forward and offered their extension as base for a core Khronos extension for Vulkan. They have a vested interested in making a cross vendor, cross platform API available.

In the foreseeable future, rasterizing renderers are unlikely to go anywhere. Rather, ray tracing for the time being can be used for additional effects that are otherwise hard to achieve. Clearly Nvidia is acknowledging this as well by providing a traditional rasterization engine that by itself is more powerful than previous generation ones. This also means that if X-Plane were to adopt ray tracing tomorrow, you could still run it on your old hardware, you’d just get extra shiny on top if you have ray tracing capable hardware.

Last but not least, this is another reason why you should stay away from the shaders! One day we’ll wake up in the glorious Vulkan future which will open the door to the glorious ray tracing future. All of this means that we’ll have to keep changing our shaders.