bevy 0.10.0

A refreshingly simple data-driven game engine and app framework
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100

//! Shows how to create a custom `Decodable` type by implementing a Sine wave.
//! ***WARNING THIS EXAMPLE IS VERY LOUD.*** Turn your volume down.
use bevy::audio::AddAudioSource;
use bevy::audio::Source;
use bevy::prelude::*;
use bevy::reflect::TypeUuid;
use bevy::utils::Duration;

// This struct usually contains the data for the audio being played.
// This is where data read from an audio file would be stored, for example.
// Implementing `TypeUuid` will automatically implement `Asset`.
// This allows the type to be registered as an asset.
#[derive(TypeUuid)]
#[uuid = "c2090c23-78fd-44f1-8508-c89b1f3cec29"]
struct SineAudio {
    frequency: f32,
}
// This decoder is responsible for playing the audio,
// and so stores data about the audio being played.
struct SineDecoder {
    // how far along one period the wave is (between 0 and 1)
    current_progress: f32,
    // how much we move along the period every frame
    progress_per_frame: f32,
    // how long a period is
    period: f32,
    sample_rate: u32,
}

impl SineDecoder {
    fn new(frequency: f32) -> Self {
        // standard sample rate for most recordings
        let sample_rate = 44_100;
        SineDecoder {
            current_progress: 0.,
            progress_per_frame: frequency / sample_rate as f32,
            period: std::f32::consts::PI * 2.,
            sample_rate,
        }
    }
}

// The decoder must implement iterator so that it can implement `Decodable`.
impl Iterator for SineDecoder {
    type Item = f32;

    fn next(&mut self) -> Option<Self::Item> {
        self.current_progress += self.progress_per_frame;
        // we loop back round to 0 to avoid floating point inaccuracies
        self.current_progress %= 1.;
        Some(f32::sin(self.period * self.current_progress))
    }
}
// `Source` is what allows the audio source to be played by bevy.
// This trait provides information on the audio.
impl Source for SineDecoder {
    fn current_frame_len(&self) -> Option<usize> {
        None
    }

    fn channels(&self) -> u16 {
        1
    }

    fn sample_rate(&self) -> u32 {
        self.sample_rate
    }

    fn total_duration(&self) -> Option<Duration> {
        None
    }
}

// Finally `Decodable` can be implemented for our `SineAudio`.
impl Decodable for SineAudio {
    type Decoder = SineDecoder;

    type DecoderItem = <SineDecoder as Iterator>::Item;

    fn decoder(&self) -> Self::Decoder {
        SineDecoder::new(self.frequency)
    }
}

fn main() {
    let mut app = App::new();
    // register the audio source so that it can be used
    app.add_plugins(DefaultPlugins)
        .add_audio_source::<SineAudio>()
        .add_startup_system(setup)
        .run();
}

fn setup(mut assets: ResMut<Assets<SineAudio>>, audio: Res<Audio<SineAudio>>) {
    // add a `SineAudio` to the asset server so that it can be played
    let audio_handle = assets.add(SineAudio {
        frequency: 440., //this is the frequency of A4
    });
    audio.play(audio_handle);
}