Cross-posted from Assembly Dev Notes

System architecture is always a risk factor when you haven’t worked on a certain kind of project, or at a certain scale before. We knew we needed scenes to be pretty well separated, loadable and unloadable, and we knew we’d need some kind of separation within scenes between the nitty-gritty of shader setup, animation declarations, update-render loops, and the higher-level logic of a scene – triggering animations in response to user interaction, fading between music tracks for different parts of the scene.

We ended up with a Scene class that handled loading, unloading, shader setup, and all the other crunchy lifecycle stuff. It then passed control to a somewhat-misnamed StateMachine class that implemented long-running cancellable async functions for managing the different sequences of a scene.

Free of all the gritty stuff, the higher-level logic was able to look something like:

class Scene010States extends StateMachine {
    entry = this.intro;

    async intro() {
        this.sound.onceThenLoop(Layer.Music, "intro", "firstLoop");

        const vo = this.vo("vo_title");
        const anim = this.playSegment("intro")

        await Promise.all([vo, anim])

        this.advanceTo(this.waitClick);
    }

    async waitClick() {
        await this.getClick();
        this.advanceTo(this.outro);
    }

    async outro() {
        await this.playSegment("outro");
        this.scene.event(SceneEvent.End);
    }
}

While imperfect (and imperfectly named) this made it super easy to iterate on the flow of a scene while someone else fiddled with materials or scenery.

Cancellation and pause/resume logic remains a bit thorny; cancellation is handled by setting a flag on the statemachine and checking that flag between states, and by helpers like vo() and playSegment() checking the flag before resolving or triggering further events. Pausing and resuming are handled by allowing all long-running tasks to register pause and resume methods for themselves. Sadly it’s a little bit case-by-case; there’s always a mismatch between long-running tasks and a regular update()/render() game loop.

Next: Oat the Goat #4: 3D Scenes