moria/src/light_balls.rs

use bevy::prelude::*;

use crate::player::Player;

const RANGE: f32 = 25.0;

pub struct LightBall;
pub fn light_up_ball_when_close_to_player(
    mut commands: Commands,
    player: Query<(&Transform, &Player), Without<LightBall>>,
    mut thingies: Query<(
        Entity,
        &Transform,
        &LightBall,
        &mut Handle<StandardMaterial>,
        Option<&mut Light>,
    )>,
    materials: Res<LightBallMaterials>,
) {
    let player_pos = if let Some(player) = player.iter().next() {
        player.0.translation
    } else {
        return;
    };

    for (entity, trans, _, mut material, light) in thingies.iter_mut() {
        let dis = trans.translation.distance(player_pos);
        if dis < RANGE {
            *material = materials.lit.clone();

            // change intensity,
            // add light if there isn't one
            if let Some(mut l) = light {
                l.intensity = 300.0 * (RANGE - dis) / RANGE;
            } else {
                commands.entity(entity).insert(Light {
                    color: Color::rgb(15.0, 15.0, 15.0),
                    intensity: 300.0 * (RANGE - dis) / RANGE,
                    ..Default::default()
                });
            }
        } else {
            *material = materials.unlit.clone();

            // remove light if there is one
            if light.is_some() {
                commands.entity(entity).remove::<Light>();
            }
        }
    }
}

pub fn spawn_light_ball(
    commands: &mut Commands,
    materials: &LightBallMaterials,
    translation: Vec3,
) {
    commands
        .spawn_bundle(PbrBundle {
            mesh: materials.mesh.clone(),
            material: materials.unlit.clone(),
            transform: Transform::from_translation(translation),
            ..Default::default()
        })
        .insert(LightBall);
}

pub struct LightBallMaterials {
    unlit: Handle<StandardMaterial>,
    lit: Handle<StandardMaterial>,
    mesh: Handle<Mesh>,
}
impl FromWorld for LightBallMaterials {
    fn from_world(world: &mut World) -> Self {
        let world = world.cell();
        let mut materials = world
            .get_resource_mut::<Assets<StandardMaterial>>()
            .unwrap();
        let mut meshes = world.get_resource_mut::<Assets<Mesh>>().unwrap();

        let mut unlit: StandardMaterial = Color::rgb(0.9, 0.9, 0.9).into();
        unlit.metallic = 0.0;
        unlit.reflectance = 0.0;
        let unlit = materials.add(unlit);

        let mut lit: StandardMaterial = Color::rgb(15.0, 15.0, 15.0).into();
        lit.metallic = 0.5;
        lit.reflectance = 0.5;
        lit.emissive = Color::rgb(15.0, 15.0, 15.0);
        let lit = materials.add(lit);

        let mesh = meshes.add(Mesh::from(shape::Icosphere {
            radius: 2.0,
            subdivisions: 5,
        }));

        Self { lit, unlit, mesh }
    }
}