Durango Display Planes



Today we present another Durango GPU custom feature shown in our first exclusive article: the display planes.

The Durango GPU supports three independent display planes, which are conceptually similar to three separate front buffers. The display planes have an implied order. The bottom plane is combined with the middle plane using the middle plane’s alpha channel as an interpolation factor. The result of this operation is combined with the top plane using the top plane’s alpha channel as an interpolation factor. Blending occurs at 10-bit fixed-point precision. The following diagram illustrates the sequence of operations.

display_planes

The three display planes are independent in the following ways, among others:

  • They can have different resolutions.
  • They can have different precisions (bits per channel) and formats (float or fixed).
  • They can have different color spaces (RGB or YCbCr, linear or sRGB).

Each display plane can consist of up to four image rectangles, covering different parts of the screen. The use of multiple screen rectangles can reduce memory and bandwidth consumption when a layer contains blank or occluded areas.

The display hardware contains three different instances of various image processing components, one per display plane, including:

  • A hardware scaler.
  • A color space converter.
  • A border cropper.
  • A data type converter.

Using these components, the GPU converts all three display planes to a common output profile before combining them.

The bottom and middle display planes are reserved for the running title. A typical use of these two planes is to render the game world at a fixed title-specified resolution, while rendering the UI at the native resolution of the connected display, as communicated over HDMI. In this way, the title keeps the benefits of high-quality hardware rescaling, without losing the pixel-accuracy and sharpness of the interface. The GPU does not require that all three display planes be updated at the same frequency. For instance, the title might decide to render the world at 60 Hz and the UI at 30 Hz, or vice-versa. The hardware also does not require the display planes to be the same size from one frame to the next.

The system reserves the top display plane for itself, which effectively decouples system rendering from title rendering. This decoupling removes certain output constraints that exist on the Xbox 360. For example, on Durango the system can update at a steady frame rate even when the title does not. The system can also render at a lower or higher resolution than the title, or with different color settings.


  • Damon Tarklin

    So what does all this mean? In layman’s terms.

    • OLars

      it means that you can potentially have more detailed images (I assume with better depth perception?) and when things like the xbox live menu popup (on the 360) it can do so in a separate frame so that it doesn’t mess with the frames displaying the video images of the media running. All in all: better graphics and better performance

  • alias

    plump poo, aka nothing…

  • TheSource

    It means that they can have UI run at 30 FPS, background animations/random npcs at 30 FPS and characters, effects etc. at 60 FPS.

    Take a fighting game for example. The lane and characters will run at 60 FPS and the background and UI at 30 FPS. This way they can get more power where it’s needed.

    Even more so they can make background/locations at lower resolution like 720p and upscale them while character models run at 1080p. It’s a brilliant way to gain more power from the GPU.

  • Fr4me

    that if hud covers 50% of the screen, the system produces as it have double power

  • Lol… This is almost exactly what I post when my news hit big on N4G, about Durango having 2 scaler chips, and being backwards compatible. People weren’t sure what to believe.. now they know. Also, I’m about to drop info on the new Durango Controller on my site, just to counter the PS4 news a tad little bit on the 20th.

  • Mhhh

    It’s just a more flexible overlay. I think the most usage will be to avoid lock contentions between foreground(game) and background(apps) when something pops up from background to the front. If they would all have access to the display it would require some semaphores which might affect the gaming experience.
    Sure you can also imagine its use for HUDs and optimize 720p/1080p benefit but I’m not sure if that’s really relevant anymore for current GPU performance.

  • Sporadik Styles

    My guess is it would have something to do with augmented reality, or 3D gaming.

  • fade2black

    “For example, on Durango the system can update at a steady frame rate even when the title does not.”
    Should the title’s framerate dip under the screens refresh rate, there would not be screen tearing, because Durango will always output @ a costant framerate, even in case of lag.

  • nirwanda

    Sounds like the simple way of adding skype while gaming and the system taking less of a hit i.e skype runs at a lower frame rate and lower res than the game so the game takes less of a hit and its easy to stick it in the top right hand corner or something on matter what your doing

  • nirwanda

    Apart from screaming skype in game chat with video calling being handled at a frame rate to match a skype call, does anyone else think there is a surgestion that the durango could be upgradable with another gpu in the future, for instance if one plane is handled by the current gpu and another by the upgrade

  • It coul mean compatibility with the Oculus Rift. Then it can render the scene in whatever resolution the HMD accepts and render the HUD on a separate resolution and plane so it doesn’t distort when being processed for the Oculus’ special output.

  • Zaur

    i was thinking they could use Onlive video decoding, stream the background or less usefull images, or even more useful important images that the xbox could not handle. Adding stream video around hardware generated imagery would also allow them to have the ultimate copyright tool. Who would want to run a burned copy of a game at some very odd image resolution?