From 135fc268aa8d3c969ef58b78b3e78e0d4cd1e27f Mon Sep 17 00:00:00 2001
From: Nixon <voxell.technologies@gmail.com>
Date: Wed, 24 Aug 2022 16:47:09 +0800
Subject: [PATCH] smooth camera follow

---
 src/game.rs | 29 ++++++++++-------------------
 1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/src/game.rs b/src/game.rs
index 1b6ef95..1f1618b 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -303,11 +303,13 @@ fn win_setup(mut commands: Commands, asset_server: Res<AssetServer>) {
 }
 
 fn move_camera(
-	mut camera_query: Query<(&Camera, &mut Transform, &GlobalTransform)>,
+	mut camera_query: Query<(&Camera, &mut Transform)>,
 	characters: Query<(&CharacterId, &Transform), Without<Camera>>,
 	level_query: Query<&SelectedCharacterId>,
+	time: Res<Time>,
 ) {
-	const MARGIN: f32 = 128.0;
+	const MARGIN: f32 = 300.0;
+	const FOLLOW_SPEED: f32 = std::f32::consts::PI;
 
 	if let Ok(selected_character_id) = level_query.get_single() {
 		if let Some(selected_character_id) = &selected_character_id.0 {
@@ -315,25 +317,14 @@ fn move_camera(
 				.iter()
 				.find(|(character_id, _transform)| *character_id == selected_character_id)
 			{
-				let (camera, mut camera_transform, camera_global_transform) =
+				let (camera, mut camera_transform) =
 					camera_query.single_mut();
 
-				let pos = camera
-					.world_to_viewport(camera_global_transform, transform.translation)
-					.unwrap();
-				let size = camera.logical_viewport_size().unwrap();
-				if pos.x < MARGIN {
-					camera_transform.translation.x += pos.x - MARGIN;
-				}
-				if pos.x > size.x - MARGIN {
-					camera_transform.translation.x += MARGIN + pos.x - size.x;
-				}
-				if pos.y < MARGIN {
-					camera_transform.translation.y += pos.y - MARGIN;
-				}
-				if pos.y > size.y - MARGIN {
-					camera_transform.translation.y += MARGIN + pos.y - size.y;
-				}
+				let size: Vec2 = camera.logical_viewport_size().unwrap();
+				let half_height: f32 = size.y * 0.5;
+				camera_transform.translation = camera_transform.translation.lerp(transform.translation, time.delta_seconds() * FOLLOW_SPEED);
+				// prevent camera from going too low
+				camera_transform.translation.y = camera_transform.translation.y.max(half_height-MARGIN);
 			}
 		}
 	}