Separate Systems/Pipelines for Update and Draw cycles

[roo-oliv]

Hi, I'm using Flecs.NET with Monogame, but this question applies to the framework, language-independent.

If I want to have a set of systems in a pipeline meant for dealing with the game's logic and another set of systems in a separate pipeline meant for drawing, how can I accomplish that using Flecs?

I'm new to Flecs, but a first read of the docs seems to assume there will always be a single pipeline. I think I can just keep swapping pipelines with World::SetPipeline. But I'm not aware if this is a misuse and can have unintended side effects on Flecs' behavior or its performance.

// Initialization
{
    ...
    var updatePipeline = world.Pipeline()
        .With(Ecs.System)
        .Without<DrawPhase>()
        .Build();
    var drawPipeline = world.Pipeline()
        .With(Ecs.System)
        .With<DrawPhase>()
        .Build();
    ...
}

// Update
{
    ...
    world.SetPipeline(updatePipeline);
    world.Progress();
    ...
}

// Draw
{
    ...
    world.SetPipeline(drawPipeline);
    world.Progress();
    ...
}

[SanderMertens]

Switching pipelines should be fast enough! You can also use world.RunPipeline(drawPipeline).

[roo-oliv]

Nice, thank you! Didn't know about World::RunPipeline! Does it make sense to add a mention to this on this page of the docs?

[roo-oliv]

Coming back here to share a side effect of using World::RunPipeline instead of World::Progress: you lose the time Info stored at the World object, so since I was relying on World.GetInfo().WorldTimeTotal for some calculations, I had to stick with World::Progress.