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QB64-Phoenix-Edition / QB64pe

The QB64 Phoenix Edition Repository
https://qb64phoenix.com
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Fix GLUT thread to redraw at an accurate 60 FPS. #474

Closed mkilgore closed 7 months ago

mkilgore commented 7 months ago

Currently the GLUT thread draws the screen too slowly, it is supposed to default to 60 FPS but you'll always get a bit less than that. This is because the current logic simply inserts delays for the entire length of a frame, not taking into account how long it took us to render the last frame. Any time spent rendering thus results in a slowed down FPS.

The new code uses GetTicks() to measure how much time has passed since the last render, which then lets us calculate the exact amount of time until the next frame so we can sleep for that amount. We additionally then measure how long the sleep lasted vs. what we asked for (since any sleep we do only has a minimum guarantee, it will occasionally last a bit longer) and adjust based on that as well. The result is a perfect 60 FPS as long as rendering is quick enough.

If the rendering falls behind (Ex. a slow _GL SUB is in the program) then we'll start skipping frames to get back on track. This is behavior may want to be talk about or perhaps make configurable, I went with basically having it drop back to 30 FPS (and then 20/15/etc.) if the rendering is too slow. The alternative would be that we just set the deltaTick back to zero and render as fast as possible.

The undocumented _FPS command can be used to change the speed from 60 FPS to whatever is desired (with a cap of 200 FPS). This was always true, but now it should be accurate to whatever you request.

Fixes: #408

mkilgore commented 7 months ago

@a740g Maybe, but the _Auto flag is not implemented so that might be a bit of a problem. Based on it's description of "make QB64 auto-adjust fps based on load" I'd rather just get rid of it, functionally we already do that - if the CPU is too slow then the FPS goes down :rofl:

What would probably be a good idea is replacing _Auto with a setting to toggle between preferring a stable FPS vs. preferring as many frames as possible under the requested FPS, but I don't really want to mess with implementing that at the moment.

grymmjack commented 7 months ago

@mkilgore will this fix the stuttering that I shared here: https://app.screencast.com/7XGWZY42TJJcE

Thank you for this contribution regardless! <3

a740g commented 7 months ago

@mkilgore will this fix the stuttering that I shared here: https://app.screencast.com/7XGWZY42TJJcE

Thank you for this contribution regardless! <3

I think it should.

Thank you @mkilgore for fixing this! You should really push the merge button now. 😁

mkilgore commented 7 months ago

@mkilgore will this fix the stuttering that I shared here: https://app.screencast.com/7XGWZY42TJJcE

Thank you for this contribution regardless! <3

Like @a740g said I think it should probably fix some of it, you should see it move at 60 FPS after this. Some of the stutter will be due to syncing between the QB64 thread and the rendering thread and that's not addressed by this. #409 would be a complete fix for that but will also require some level of code modification to use.