An Overview

Let’s take a closer look than we had at the GTX 1080 announcement

NVIDIA's Ansel Technology
Ansel is a utility that expands the concept of screenshots along the direction of photography. When fully enabled, it allows the user to capture still images with HDR exposures, gigapixel levels of resolution, 360-degree views for VR, 3D stereo projection, and post-processing filters, all from either the game's view, or from a free-roaming camera (if available). While it must be implemented by the game developer, mostly to prevent the user from either cheating or seeing hidden parts of the world, such as an inventory or minimap rendering room, NVIDIA claims that it is a tiny burden.
  • – NVIDIA blog claims "GTX 600-series and up"
  • – UI/UX is NVIDIA controlled
    • Allows NVIDIA to provide a consistent UI across all supported games
    • Game developers don't need to spend UX and QA effort on their own
  • – Can signal the game to use its highest-quality assets during the shot
  • – NVIDIA will provide an API for users to create their own post-process shader
    • Will allow access to Color, Normal, Depth, Geometry, (etc.) buffers
  • – When asked about implementing Ansel with ShadowPlay: "Stay tuned."


“In-game photography” is an interesting concept. Not too long ago, it was difficult to just capture the user's direct experience with a title. Print screen could only hold a single screenshot at a time, which allowed Steam and FRAPS to provide a better user experience. FRAPS also made video more accessible to the end-user, but it output huge files and, while it wasn't too expensive, it needed to be purchased online, which was a big issue ten-or-so years ago.

Seeing that their audience would enjoy video captures, NVIDIA introduced ShadowPlay a couple of years ago. The feature allowed users to, not only record video, but also capture the last few minutes. It did this with hardware acceleration, and it did this for free (for compatible GPUs). While I don't use ShadowPlay, preferring the control of OBS, it's a good example of how NVIDIA wants to support their users. They see these features as a value-add, which draw people to their hardware.

Ansel comes from that same mindset, but with still photography the starting point. When activated, Ansel freezes time and allows the user to set up the perfect camera angle with a free-flying camera, add filters, and save a high-resolution image, currently up to 4.5 gigapixels but NVIDIA could raise that if users honestly need more. (1080p is ~2 megapixels.) This can be 2D, stereoscopic 3D, or a whole 360-degree photo-bubble (with an equirectangular projection). It can also be saved as an HDR image (in the EXR format) to adjust the exposure in an image editing program like Photoshop. They can also be modified from within Ansel with filters, which could be provided by either NVIDIA, or custom-made from the game's many buffers.

Say what you like about Instagram, but it shows that the urge to share expressive still images is not limited to those who were called to photography. Not everyone will be good at it, but more good content is produced as the tools get easier and cheaper. I don't know if they're attempting to move existing members of this subculture toward NVIDIA with these tools, but it might compel existing users to get used to it… and to keep choosing green whenever they want more performance.

This brings me to “who can use it?” According to the press briefing, this feature will be available to both Maxwell and Pascal. According to their blog, however, it “will be available on supported games for NVIDIA GeForce GTX 600-series and up.” This means that it will also work on Kepler, barring some terrible typo. Either way, NVIDIA is not locking it down to Pascal, which makes sense because older cards might be due for an upgrade.

Zooming In

Ansel will not be available for every game. It is an SDK, which means that it must be compiled in by the game developer. NVIDIA originally targeted “one line of code” to implement Ansel, but that later expanded to the order of about a hundred lines, give or take a few dozen. That's still a miniscule burden, though, which is required for such a niche feature (otherwise, basically no-one would implement it). It should be just enough for the developer to prevent Ansel from being used to cheat.

NVIDIA provides two examples of effort required to integrate Ansel. The Witness, a puzzle game from indie developer, Jonathan Blow, added the feature with about 40 lines of code. The Witcher 3 needed a little more effort, with a reported ~150 extra lines required for Ansel. This metric cannot quantify the burden on QA, which is something to look at post-launch, but making the feature painless is clearly a top-priority design goal.

Part of the reason for such a small line-of-code count is that NVIDIA controls the user interface. All of the sliders and options will be consistent from game to game. This is good for the game developer, because programming (and testing) a user interface takes a lot of time and effort, and designing a special one for a handful of GeForce gamers would be as low priority as it gets. This is also good for NVIDIA, because their users will have basically no learning curve as they travel between titles. So long as NVIDIA's implementation is complete and intuitive, it's a win-win.

Ansel's user interface as seen within The Witcher III
Again, this should be consistent across all supported titles, as it's NVIDIA's UX.

As I briefly mentioned earlier, Ansel will be able to access more than just the final image. Many games are based on a deferred rendering method, which means that the engine generates several buffers independently. This is very fast, especially for scenes with complex, dynamic lighting, although it doesn't play nice with anti-aliasing and a few other effects.

Ansel can access some or all of these buffers, which lets it know about the object's depth, surface normal orientation, base color, lighting, and so forth. This can drive much more complex filters than would otherwise be possible, in Photoshop or other editors, because it retains information about the scene. NVIDIA lists a bunch of effects that will ship with Ansel, such as color correction and lightshafts, but they are also implementing an SDK for users to add their own. It is unclear whether this is HLSL, whatever shading language the game compiles down into, or a special language just for Ansel, but I'm excited to see what we can achieve when we have access to the game's intermediate buffers.

While only a handful of games support capturing their depth buffer at the moment, so NVIDIA isn't announcing anything yet, users should be able to even adjust properties like focal length and depth of field. These are things that you cannot do correctly from a screenshot.

Of course, while we now know that Ansel is an SDK, that wasn't clear until a few minutes into that section of their GTX 1080 press event. Intercepting 3D data from within video games has been done before, such as Adobe's Acrobate 3D Capture, but this would be a ridiculous task nowadays with games as programmable as they are. At the time, when NVIDIA announces a technology like this with no background, I started to question my understanding of reality. Did they figure something out? Are they doing some crazy, per-game profile?

Nope! The developer is involved, and that's a good thing.

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