Smooth Animation, but lots of jaggy edges

You'd think a game loop wouldn't be a hard thing.

while(true) {

  process_input();

  update_game_logic();

  render();

}

That can be adequate for a lot of simple games, but the cool thing to do is to decouple the update calls from the render calls, update on a fixed (sim) clock, and render as often as you can, using a very lightweight interpolation inside the render loop to smooth the trajectories between update calls.

In particular, I'm using a version from Robert Nystrom's "Game Programming Patterns", which looks like this in my language:

 loop {

    float currentTime = get_current_time();

    float elapsedTime = currentTime - previousTime;

    previousTime = currentTime;

    lag = lag + elapsedTime;

    

    sdl_tick_input();

    if (sdl_quit_signalled() == 1) {

      break;

    }

    while (lag >= SECONDS_PER_UPDATE) {

      update();

      lag = lag - SECONDS_PER_UPDATE;

      updates = updates + 1;

    }

    float alpha = lag / SECONDS_PER_UPDATE;

    draw(alpha);

    renders = renders + 1;

  }

The nice thing about this is that the updates are always at a fixed rate, so the simulations don't go unstable, and you still get to render as often as your machine is capable of. I could stick an artificial delay in there to keep the frame rate from going too high (rarely a problem, but if I wanted to conserve battery power on portable devices (phones, tablets, laptops) it might be worth considering.

Several bits that I ran into along the way that I need to clean up:

• I'm being sloppy about pointers within my compiler. I just throw an extra load() to dereference the pointer, and things seem to work out, but it feels super sloppy.
• I'm getting a segmentation fault about 13 seconds into the run. Don't know why that is, but it's reproducible. Which is a nice thing for a crash bug.
• I've got user-defined data types (let's call them "structs"). But if I create them at global scope, they don't get linked properly. Gotta figure that out.

I was hoping to get the ship to fly around with simulated intention by this point. That's soon, but not yet, I guess.