避免在glium中丟幀

Question

我使用glium作為我的opengl綁定，但是不可能獲得可靠的60 FPS。

最小的測試用例是

#[macro_use]
extern crate glium;
extern crate clock_ticks;

use glium::Surface;
use glium::glutin;

fn main() {
    use glium::DisplayBuild;

    let display = glutin::WindowBuilder::new()
        .build_glium()
        .unwrap();

    let frames = 60 * 5;
    let trials = 3;

    for _ in 0.. trials {
        let start_ns = clock_ticks::precise_time_ns();
        for _ in 0..frames {
            display.draw().finish().unwrap();
        }

        let duration_ns = clock_ticks::precise_time_ns() - start_ns;
        let duration_s = (duration_ns as f64) / 1_000_000_000f64;
        let fps = (frames as f64) / duration_s;
        let dropped = (duration_s - (frames as f64 * (1f64/60f64))) / (1f64/60f64);

        println!("{} frames in {:.6} seconds = {:.3} fps (estimated {:.1} frames dropped)", frames, duration_s, fps, dropped);
    }
}

我期望60 FPS，但在我運行它時經常顯示59 FPS（在OSX中）。 該項目可在github上獲得，以便於編譯和運行。

有什么方法可以調整glium以便它不會丟幀嗎？ OSX覆蓋了vsync設置，因此無法在每個幀之間等待vsync。

Answer 1

是的，就像@ 8bitree一樣，我懷疑你的測量不正確，而不是實際問題。 在我的系統上，Debian：

steve@warmachine:~/tmp/guess$ cargo run
     Running `target/debug/guess`
300 frames in 4.427656 seconds = 67.756 fps (estimated -34.3 frames dropped)
300 frames in 0.006892 seconds = 43529.834 fps (estimated -299.6 frames dropped)
300 frames in 0.006522 seconds = 45997.412 fps (estimated -299.6 frames dropped)
steve@warmachine:~/tmp/guess$ cargo run
     Running `target/debug/guess`
300 frames in 4.953447 seconds = 60.564 fps (estimated -2.8 frames dropped)
300 frames in 4.999410 seconds = 60.007 fps (estimated -0.0 frames dropped)
300 frames in 1.608712 seconds = 186.485 fps (estimated -203.5 frames dropped)

所以，是的，有點......奇怪。