On 2018-04-10 07:25 PM, Cyr, Aric wrote: >> From: Michel Dänzer [mailto:michel at daenzer.net] >> On 2018-04-10 07:13 PM, Cyr, Aric wrote: >>>> From: Michel Dänzer [mailto:michel at daenzer.net] >>>> On 2018-04-10 06:26 PM, Cyr, Aric wrote: >>>>> From: Koenig, Christian Sent: Tuesday, April 10, 2018 11:43 >>>>> >>>>>> For video games we have a similar situation where a frame is rendered >>>>>> for a certain world time and in the ideal case we would actually >>>>>> display the frame at this world time. >>>>> >>>>> That seems like it would be a poorly written game that flips like >>>>> that, unless they are explicitly trying to throttle the framerate for >>>>> some reason. When a game presents a completed frame, theyâ??d like >>>>> that to happen as soon as possible. >>>> >>>> What you're describing is what most games have been doing traditionally. >>>> Croteam's research shows that this results in micro-stuttering, because >>>> frames may be presented too early. To avoid that, they want to >>>> explicitly time each presentation as described by Christian. >>> >>> Yes, I agree completely. However that's only truly relevant for fixed >>> refreshed rate displays. >> >> No, it also affects variable refresh; possibly even more in some cases, >> because the presentation time is less predictable. > > Yes, and that's why you don't want to do it when you have variable refresh. The hardware in the monitor and GPU will do it for you, so why bother? > The input to their algorithms will be noisy causing worst estimations. If you just present as fast as you can, it'll just work (within reason). If a frame is presented earlier than the time corresponding to the state of the world as displayed in the frame, it results in stutter, just as when it's presented too late. > The majority of gamers want maximum FPS for their games, and there's quite frequently outrage at a particular game when they are limited to something lower that what their monitor could otherwise support (i.e. I don't want my game limited to 30Hz if I have a shiny 144Hz gaming display I paid good money for). That doesn't (have to) happen. See https://www.gdcvault.com/play/1025407/Advanced-Graphics-Techniques-Tutorial-The for Croteam's talk about this at this year's GDC. It says the best API available so far is the Vulkan extension VK_GOOGLE_display_timing, which (among other things) allows specifying the earliest desired presentation time via VkPresentTimeGOOGLE::desiredPresentTime . (The talk also mentions that they previously experimented with VDPAU, because it allows specifying the target presentation time) -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
