From f53cd2f848e710ce16008f4d96afe23443c86627 Mon Sep 17 00:00:00 2001
From: Joe Ardent <code@ardent.nebcorp.com>
Date: Thu, 6 Jan 2022 23:58:38 -0800
Subject: [PATCH] Add collision detection, reaction, and gravity.

---
 src/flycam.rs | 94 +++++++++++++++++++++++++++------------------------
 src/main.rs   | 47 +++++++++++++-------------
 2 files changed, 73 insertions(+), 68 deletions(-)

diff --git a/src/flycam.rs b/src/flycam.rs
index 48a717c..be52d2a 100644
--- a/src/flycam.rs
+++ b/src/flycam.rs
@@ -15,17 +15,12 @@ use heron::{
 pub const PLANET_RADIUS: f32 = 75.0;
 
 const PLAYER_DIST: f32 = PLANET_RADIUS + 100.0;
-const CAM_DIST: f32 = 30.0;
+const CAM_DIST: f32 = 50.0;
 
 #[derive(Component, Default)]
 struct PlayerState {
     velocity: Vec3,
-}
-
-#[derive(Default)]
-struct UpState {
-    player_up: Vec3,
-    cam_up: Vec3,
+    colliding: bool,
 }
 
 #[derive(Default)]
@@ -49,7 +44,7 @@ impl Default for MovementSettings {
         Self {
             sensitivity: 1.0,
             accel: 40.,
-            drag: 0.05,
+            drag: 0.0005,
             gravity: 10.0,
         }
     }
@@ -123,28 +118,20 @@ fn setup_dbg_ui(mut commands: Commands, asset_server: Res<AssetServer>) {
         .insert(UpText);
 }
 
-fn dbg_ui_system(state: Res<UpState>, mut query: Query<&mut Text, With<UpText>>) {
-    let cos = state.player_up.dot(state.cam_up);
-
-    let mut text = query.single_mut();
-    text.sections[0].value = format!(
-        "up: {:?}\ncam_up: {:?}\ntheta: {:.2}",
-        state.player_up,
-        state.cam_up,
-        cos.acos().to_degrees()
-    );
+fn ui_system(pstate_query: Query<&PlayerState>, mut text_query: Query<&mut Text, With<UpText>>) {
+    let mut text = text_query.single_mut();
+    let pstate = pstate_query.single();
+    text.sections[0].value = format!("{:.2}", pstate.velocity.length());
 }
 
 fn player_move(
     time: Res<Time>,
-    _settings: Res<MovementSettings>,
-    mut up_state: ResMut<UpState>,
-    mut bike_query: Query<(&mut Transform, &mut PlayerState), Without<FlyCam>>,
+    mut bike_query: Query<(&mut Transform, &PlayerState), Without<FlyCam>>,
     mut cam_query: Query<(&mut Transform, &FlyCam), Without<PlayerState>>,
 ) {
     let dt = time.delta_seconds();
 
-    let (mut bike_xform, mut player_state) = bike_query.single_mut();
+    let (mut bike_xform, player_state) = bike_query.single_mut();
     let up = bike_xform.translation.normalize();
     let cam_up = bike_xform.up();
     let cos = up.dot(cam_up);
@@ -170,15 +157,9 @@ fn player_move(
     }
 
     if player_state.velocity.is_finite() {
-        //state.velocity += -up * settings.gravity * dt;
         bike_xform.translation += player_state.velocity * dt;
-    } else {
-        //state.velocity = -up * settings.gravity * dt;
     }
 
-    up_state.cam_up = cam_up;
-    up_state.player_up = up;
-
     let (mut cam_xform, _) = cam_query.single_mut();
     cam_xform.translation = bike_xform.translation + (up * CAM_DIST);
     cam_xform.look_at(bike_xform.translation, Vec3::Y);
@@ -247,26 +228,49 @@ fn player_look(
 
     transform.rotate(rotation);
 
-    //dbg!(&vel);
-
     pstate.velocity = vel;
 }
 
-fn cursor_grab(
-    keys: Res<Input<KeyCode>>,
-    mut windows: ResMut<Windows>,
-    mut query: Query<(&FlyCam, &mut Transform)>,
+fn collision_detection(
+    mut events: EventReader<CollisionEvent>,
+    mut query: Query<&mut PlayerState>,
 ) {
-    let window = windows.get_primary_mut().unwrap();
-    if keys.just_pressed(KeyCode::L) {
-        let (_, mut transform) = query.single_mut();
-        *transform.as_mut() = transform.looking_at(Vec3::ZERO, Vec3::Y);
+    let mut pstate = query.single_mut();
+
+    for event in events.iter() {
+        if let CollisionEvent::Started(_, _) = event {
+            pstate.colliding = true;
+        } else {
+            pstate.colliding = false;
+        }
     }
-    if keys.just_pressed(KeyCode::U) {
-        let lock = !window.cursor_locked();
-        window.set_cursor_lock_mode(lock);
-        window.set_cursor_visibility(lock);
+}
+
+fn gravity_collision_reaction(
+    time: Res<Time>,
+    settings: Res<MovementSettings>,
+    mut query: Query<(&mut PlayerState, &Transform)>,
+) {
+    let dt = time.delta_seconds();
+    let g = settings.gravity;
+    let (mut pstate, xform) = query.single_mut();
+
+    // first gravity
+    let down = -xform.translation.normalize();
+    let dvel = down * g * dt;
+    let mut vel = if pstate.velocity.is_finite() {
+        pstate.velocity + dvel
+    } else {
+        dvel
+    };
+
+    // now see if we're currently colliding
+    if pstate.colliding {
+        let dvel = down * vel.dot(down) * 1.02;
+        vel -= dvel;
     }
+
+    pstate.velocity = vel;
 }
 
 /// Contains everything needed to add first-person fly camera behavior to your
@@ -277,12 +281,12 @@ impl Plugin for PlayerPlugin {
         app.init_resource::<PlayerState>()
             .init_resource::<MovementSettings>()
             .init_resource::<InputState>()
-            .init_resource::<UpState>()
             .add_startup_system(setup_player)
             .add_startup_system(setup_dbg_ui)
-            .add_system(dbg_ui_system)
+            .add_system(ui_system)
             .add_system(player_move.label("move"))
             .add_system(player_look.after("move"))
-            .add_system(cursor_grab);
+            .add_system(collision_detection)
+            .add_system(gravity_collision_reaction);
     }
 }
diff --git a/src/main.rs b/src/main.rs
index c4d53a2..813a078 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,13 +1,8 @@
 use bevy::prelude::*;
 use cyber_rider::flycam::{MovementSettings, PlayerPlugin, PLANET_RADIUS};
+use heron::prelude::*;
 
-/*
-stolen with neither shame nor pity from
-git@github.com:sburris0/bevy_flycam.git, b90f6fc, which is copyright 2020
-Spencer Burris
-*/
-
-const LIGHT_RANGE: f32 = PLANET_RADIUS * 2.2;
+const LIGHT_RANGE: f32 = PLANET_RADIUS * 0.6;
 const LIGHT_DIST: f32 = PLANET_RADIUS * 1.2;
 
 fn main() {
@@ -15,6 +10,7 @@ fn main() {
         .insert_resource(Msaa { samples: 4 })
         .add_plugins(DefaultPlugins)
         .add_plugin(PlayerPlugin)
+        .add_plugin(PhysicsPlugin::default())
         .insert_resource(MovementSettings {
             sensitivity: 0.3, // default: 1.0
             accel: 20.0,      // default: 40.0
@@ -43,21 +39,21 @@ fn setup(
     mut materials: ResMut<Assets<StandardMaterial>>,
 ) {
     let red_light = PointLight {
-        intensity: 5_000.0,
+        intensity: 1_000.0,
         range: LIGHT_RANGE,
         color: Color::RED,
         ..Default::default()
     };
 
     let blue_light = PointLight {
-        intensity: 5_000.0,
+        intensity: 1_000.0,
         range: LIGHT_RANGE,
         color: Color::BLUE,
         ..Default::default()
     };
 
     let purple_light = PointLight {
-        intensity: 5_000.0,
+        intensity: 1_000.0,
         range: LIGHT_RANGE,
         color: Color::PURPLE,
         ..Default::default()
@@ -69,20 +65,25 @@ fn setup(
     });
 
     // world
-    commands.spawn_bundle(PbrBundle {
-        mesh: meshes.add(Mesh::from(shape::Icosphere {
-            radius: PLANET_RADIUS,
-            subdivisions: 6,
-        })),
-        material: materials.add(StandardMaterial {
-            base_color: Color::GRAY,
-            metallic: 0.7,
-            perceptual_roughness: 0.5,
-            ..Default::default()
-        }),
+    commands
+        .spawn_bundle(PbrBundle {
+            mesh: meshes.add(Mesh::from(shape::Icosphere {
+                radius: PLANET_RADIUS,
+                subdivisions: 6,
+            })),
+            material: materials.add(StandardMaterial {
+                base_color: Color::GRAY,
+                metallic: 0.7,
+                perceptual_roughness: 0.5,
+                ..Default::default()
+            }),
 
-        ..Default::default()
-    });
+            ..Default::default()
+        })
+        .insert(RigidBody::Static)
+        .insert(CollisionShape::Sphere {
+            radius: PLANET_RADIUS,
+        });
 
     // east light
     commands