Post by Filmstars in BATTY VAMPS jam comments

Game felt much faster than last time, took a bit to get used to. Think the movement is very sick now - it’s hard, but after a while, managing to land those flights right on the victim, is awesome. (But fwiw I also enjoyed the slower paced gliding nature of previous version.)

The collision seems to have issues, though. At first I thought it was skill issue that I usually collide twice or more when touching ground, but at the very end of the footage I downright clipped into a building and collided 8 times in a row or so. I don’t know, some collision penalty is obviously required to make the gameplay work, but current version feels too random and sensitive.

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frenchfriesguy260 days ago

Game felt much faster than last time, took a bit to get used to.

This is actually a huge bug, it's running at ~85 fps for you when it's supposed to be limited to ~60. You're playing the game in ~1.4x speed!

This is happening because emscripten (the web build library) isn't obeying the fps I'm sending it in Firefox. I hacked it to work in my Firefox by sending it 120 (which gives me 60 for some bizarre reason), but it seems for you that's giving you a different number. What OS and Firefox version are you running? I'm going to have to figure out why this is being so weird.

I feel bad you played a bugged version for so long.. but thanks for the video, it's a big help to be able to see what people do and what their flying style is.

The collisions are definitely hacky and not good and it's high on my list to fix them. I think the reason you had such difficulty with the ground is that you were less likely to flap because your game was bugged to be so fast already. Flapping gives you a boost upwards as well as forwards. If you're not flapping a lot and getting the upwards boost, it's easier to scrape against the ground.

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Filmstars260 days ago

Ah, good old emscripten timing issues. If the framerate targeter uses emscripten_sleep under the hood, you have no chance of getting it to work the same on all browsers. I’ve been there. Best is to decouple the logic framerate from graphics framerate.

This was Firefox v123 on Arch.

I feel bad you played a bugged version for so long..

Honestly it was wicked. Felt like Quake3.

you had such difficulty with the ground is that you were less likely to flap

Yeah, I’m not sure, I usually tried just steering up from the ground, but it felt like often that steering was going into the wrong direction. Maybe because the bat is spinning? Might be skill issue. You can see me toggle Inverted Y a couple times in the video, because I confused it so often…)

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frenchfriesguy260 days ago (1 edit)

Best is to decouple the logic framerate from graphics framerate.

I do have separate timing for each of these (or i do in win32, but removed in web to try to play with emscripten), is there a way in emscripten to let the renderer do whatever but get my gaurenteed 60hz tick? Maybe I should just do a while(true) and give up on the emscripten loop.

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Filmstars260 days ago (2 edits)

What I do is this:

Keep target timestamp, when next tick is supposed to occur. Sleep aiming for this target or next graphics frame, whichever comes earlier.
Whenever code wakes up - assume any amount of time may have passed
Check against target: If only 1 tick has passed, set new target = (old_target(!) + tickrate). This is the FPS-independent steady logical tickrate.
If more than 1 tick has passed, advance by only 1 tick (avoid frame skip - effectively pause game if tab is not focused). Then set new target=now. Obviously it’s also an option to spin through some or all missed ticks, might be desired if tickrate is not RTS-tier low…
Now draw, in case the time has come for a new graphics frame

let the renderer do whatever but get my gaurenteed 60hz tick?

You’re completely at the browser’s mercy. Usually there is e.g. a hard-limit of one wakeup per second on tabs that are not being shown. If a tab is open, the invocations are still wildly inaccurate from a gamedev pov. emscripten_sleep(10) will wake up after 8-30 ms, depending on browser and os.

setTimeout is already inaccurate, and emscripten_sleep is just a very bad/clever hack that unravels the current stack, stores it and schedules a task with setTimeout which will restore that stack and resume its execution.

My hack against this is to call emscripten_sleep with only 75% of the time I actually want to be delayed, and to never even call it with values lower than 8 ms, but rather just skip those 8 ms and move on directly.

Sdlcoven is now my only emscripten-based web version. The others are based on winit, which is a pain to build around, but nicely communicates "browser requests a draw" (browser always Vsyncs btw.) versus "you wake up because of an event / because you asked to be woken up." It makes for very fluid rendering and gameplay, if it is wired up correctly.

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frenchfriesguy259 days ago

Ok wow that's pretty interesting and informative, thx. So after writing my last post I decided to try requesting 999 (as big a number as possible) and then doing my WaitTime (raylib function) call at the start of the game loop. I only wait to try to get as close to my 60hz tick as possible. Then the rest of my game loop is the same as win32: if it's time to do logic, do it, if it's time to render, do it (basically what you wrote). This gets me pretty close in Firefox (~58) and exactly 60 in Chrome. Just deployed that change so I'm curious what your Firefox gets since you've been the big outlier.

raylib WaitTime seems to call nanosleep?? No idea what that's calling in web, I'm not compiling emscripten with ASYNC so I don't think I have access to emscripten_sleep without that compiler switch.

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Filmstars259 days ago(+1)

Now shows a 59 in the corner. Very mellow experience.

raylib WaitTime seems to call nanosleep?? No idea what that's calling in web, I'm not compiling emscripten with ASYNC

Ooh, very interesting. The libc sleep functions in emscripten should do nothing without -sASYNCIFY. Maybe it is already busy-spinning.

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Cybershrooms235 days ago

Game felt much faster than last time, took a bit to get used to.

Frame rate wasn't limited to me either it seems, I was playing at 180 fps!

The fast speed of it did make it more enjoyable though.

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frenchfriesguy235 days ago

oh that's bizarre. I can't believe how hard it is to find a consistent way to manage time in the browser. What browser, version, and os are you on?

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