main.rs

use bevy::prelude::*;
fn main() {
    App::new()
        .insert_resource(ClearColor(Color::rgb(0.0, 0.0, 0.0)))
        .insert_resource(WindowDescriptor {
            title: "Grid".into(),
            width: 750.0,
            height: 750.0,
            ..Default::default()
        })
        .insert_resource(Msaa { samples: 4 })
        .add_plugins(DefaultPlugins)
        .add_startup_system_to_stage(StartupStage::Startup, setup_system)
        .add_system(draw)
        //.add_startup_system_to_stage(StartupStage::PostStartup, draw_grid)
        .run();
}

#[derive(Component, Clone, Debug)]
struct Grid {
    spacing: Vec2,
    z_rotation: f32,
    matrix: Mat4,
}

enum GridAlign {
    BottomLeft,
    BottomRight,
    TopLeft,
    TopRight,
    Center,
    NotImplemented,
}

struct GridPosition {
    alignment: GridAlign,
    position: Vec3,
}

impl Grid {
    fn new(spacing: Vec2, scale: Vec3, z_rotation: f32) -> Self {
        Self {
            spacing,
            z_rotation,
            matrix: Mat4::from_scale(scale) * Mat4::from_rotation_z(z_rotation),
        }
    }

    fn Position(&self, x: i32, y: i32, grid_align: GridAlign) -> Vec3 {
        let pos = match grid_align {
            GridAlign::BottomLeft => {
                Vec3::new(x as f32 * self.spacing.x, y as f32 * self.spacing.y, 0.0)
            }
            GridAlign::Center => Vec3::new(
                (x as f32 * self.spacing.x) + (self.spacing.x * 0.5),
                (y as f32 * self.spacing.y) + (self.spacing.y * 0.5),
                0.0,
            ),
            GridAlign::BottomRight => Vec3::new(
                (x as f32 * self.spacing.x) + (self.spacing.x),
                (y as f32 * self.spacing.y),
                0.0,
            ),
            _ => Vec3::new(x as f32 * self.spacing.x, y as f32 * self.spacing.y, 0.0),
        };
        self.matrix.transform_point3(pos)
    }
}

fn setup_system(mut commands: Commands, asset_server: Res<AssetServer>) {
    let grid = Grid::new(
        Vec2::new(50.0, 50.0),
        Vec3::ONE - (Vec3::Y * 0.35),
        0.7853982,
    );

    commands.insert_resource(grid.clone());

    // Bevy 0.7
    commands.spawn_bundle(OrthographicCameraBundle::new_2d());

    // Bevy 0.8
    // commands.spawn_bundle(Camera2dBundle::default());
}

fn draw(mut commands: Commands, asset_server: Res<AssetServer>, grid: Res<Grid>) {
    commands.spawn_bundle(SpriteBundle {
        transform: Transform {
            translation: grid.Position(0, 0, GridAlign::BottomLeft) + (Vec3::Z * 5.0),
            rotation: Quat::from_rotation_z(0.0),
            scale: Vec3::new(1., 1., 1.),
            ..Default::default()
        },
        sprite: Sprite {
            //custom_size: Some(Vec2::new(1.0, 1.0)),
            ..Default::default()
        },
        texture: asset_server.load("iso2.png"),
        ..Default::default()
    });
}