Implement object drafting

Relates to #23.

crates/objects/Cargo.toml

@@ -14,6 +14,7 @@ de_map = { path = "../map", version = "0.1.0-dev" }
 bevy = "0.7.0"
 iyes_loopless = "0.5.1"
 iyes_progress = { version = "0.3.0", features = [ "iyes_loopless" ] }
+glam = "^0.20.2"
 parry2d = { git = "https://github.com/Indy2222/parry", branch = "feature/dilation" }
 parry3d = "0.9.0"
 enum-map = "2.3.0"

crates/objects/src/draft.rs

@@ -0,0 +1,43 @@
+//! This module implements a Bevy plugin for drafting new objects on the map.
+//! This serves mostly as a visual guide for the user to correctly place new
+//! structures on the map.
+
+use bevy::prelude::*;
+use de_core::{objects::ObjectType, state::GameState};
+use iyes_loopless::prelude::*;
+
+use crate::ObjectCache;
+
+pub(crate) struct DraftPlugin;
+
+impl Plugin for DraftPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_system(new_draft.run_in_state(GameState::Playing));
+    }
+}
+
+/// This is a marker component.
+///
+/// An entity with this component is considered to be a (construction) draft.
+/// Its model will be automatically spawned by a system in this module.
+///
+/// An entity marked as a draft must have components
+/// [`bevy::transform::components::Transform`] and
+/// [`de_core::objects::ObjectType`].
+#[derive(Component)]
+pub struct Draft;
+
+fn new_draft(
+    mut commands: Commands,
+    drafts: Query<(Entity, &ObjectType), With<Draft>>,
+    cache: Res<ObjectCache>,
+) {
+    for (entity, object_type) in drafts.iter() {
+        commands
+            .entity(entity)
+            .remove::<Draft>()
+            .with_children(|parent| {
+                parent.spawn_scene(cache.get(*object_type).scene());
+            });
+    }
+}

crates/objects/src/lib.rs

@@ -5,12 +5,15 @@ use bevy::{app::PluginGroupBuilder, prelude::PluginGroup};
 use cache::CachePlugin;
 pub use cache::ObjectCache;
 pub use collider::{ColliderCache, ObjectCollider};
+pub use draft::Draft;
+use draft::DraftPlugin;
 pub use ichnography::{Ichnography, IchnographyCache};
 pub use spawner::SpawnEvent;
 use spawner::SpawnerPlugin;
 
 mod cache;
 mod collider;
+mod draft;
 mod ichnography;
 mod loader;
 mod spawner;
@@ -19,6 +22,6 @@ pub struct ObjectsPluginGroup;
 
 impl PluginGroup for ObjectsPluginGroup {
     fn build(&mut self, group: &mut PluginGroupBuilder) {
-        group.add(CachePlugin).add(SpawnerPlugin);
+        group.add(CachePlugin).add(SpawnerPlugin).add(DraftPlugin);
     }
 }