CODEWITHSUNDEEP
rustbevy
STF_ZBR
STF_ZBR

Reputation: 667

Why does Bevy have trouble drawing my many SpriteComponents?

The following program is a very minimalistic example of a large quantity of SpriteComponents. In this example, with an FPS counter, you can see how costly SpriteComponents seem to be.

I did notice that if I reuse the material handle, it does speed things up, but even still, the speed is incredibly slow. Also, I'm not certain how safe it is to reuse a material handle. I noticed in the breakout example, they did not reuse handles.

Still, with no additional systems I am getting around 10 frames per second.

use bevy:: {
    prelude::*,
};

struct Box;
struct Name(String);
#[derive(Default)]
struct FPSCounter(Timer,u32);


const WIDTH: f32 = 640.0;
const HEIGHT: f32 = 480.0;

pub struct drawPlugin;

impl Plugin for drawPlugin {
    fn build(&self, app: &mut AppBuilder) {
        app
            .add_resource(FPSCounter(Timer::from_seconds(1.0,true),0))
            .add_startup_system(setup.system())
            .add_system(fps_counter.system());
    }
}

fn fps_counter(time: Res<Time>, mut timer: ResMut<FPSCounter>) {
    timer.0.tick(time.delta_seconds);
    timer.1 += 1;
    if timer.0.finished {
        println!("One-{}",timer.1);
        timer.1 = 0;
    }
}

fn main() {
    App::build()
        .add_resource(WindowDescriptor {
            title: "Test Prog!".to_string(),
            width: WIDTH as u32,
            height: HEIGHT as u32,
            vsync: true,
            resizable: false,
            ..Default::default()
        })
        .add_default_plugins()
        .add_plugin(drawPlugin)
        .run();
}

fn setup(mut cmds: Commands, mut mats: ResMut<Assets<ColorMaterial>>,asset_server: Res<AssetServer>) {
    const sq_width: f32 = 10.0;
    const sq_height: f32 = 10.0;
    let left = -(WIDTH /2.0) + sq_width / 2.0;
    let right = (WIDTH / 2.0) - sq_width / 2.0;
    let top = (HEIGHT / 2.0) - sq_height / 2.0;
    let bot = -(HEIGHT / 2.0) + sq_height / 2.0;
    let mymat = mats.add(Color::rgb(1.0,0.0,0.0).into());
    cmds
    .spawn(Camera2dComponents::default())
    .spawn(UiCameraComponents::default());
    for box_num2 in 1..=30 {
        for box_num in 1..=30 {
            cmds.spawn(SpriteComponents {
                material: mymat,
                translation: Translation(Vec3::new(left + ((sq_width + 1.0) * box_num as f32),top - ((sq_height + 1.0) * box_num2 as f32),0.0)),
                sprite: Sprite {
                    size: Vec2::new(sq_width,sq_height),
                },
                ..Default::default()
            }).with(Box {}).with(Name("Box1".to_string()));
        }
    }
}

Upvotes: 2

Views: 2566

Answers (1)

will-hart
will-hart

Reputation: 3831

There are probably several things here.

  1. Bevy doesn't do any batching in the renderer yet,
  2. Rust debug modes are slow, this is discussed here https://github.com/bevyengine/bevy/issues/346.

Sounds like this is mostly issue two for you. To work around this you can run debug mode with some optimisations set in your cargo.toml. For instance I have

[profile.dev]
opt-level = 3

This makes initial builds a bit slower but after that it doesn't seem to make too much difference to build times. You might find you need to adjust or remove this setting if you want to do more detailed debugging.

Upvotes: 2

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