Display movement speed in gui

src/hud.rs

@@ -1,7 +1,9 @@
+use crate::player::PlayerMarker;
 use bevy::{
   diagnostic::{Diagnostics, FrameTimeDiagnosticsPlugin},
   prelude::*,
 };
+use bevy_rapier3d::{physics::RigidBodyHandleComponent, rapier::dynamics::RigidBodySet};
 
 pub struct HudPlugin;
 
@@ -10,12 +12,13 @@ impl Plugin for HudPlugin {
     app
       .add_plugin(FrameTimeDiagnosticsPlugin::default())
       .add_startup_system(setup.system())
-      .add_system(fps_update_system.system());
+      .add_system(fps_update_system.system())
+      .add_system(speed_update_system.system());
   }
 }
 
-// A unit struct to help identify the FPS UI component, since there may be many Text components
 struct FpsText;
+struct SpeedText;
 
 fn fps_update_system(diagnostics: Res<Diagnostics>, mut query: Query<&mut Text, With<FpsText>>) {
   for mut text in query.iter_mut() {
@@ -27,11 +30,28 @@ fn fps_update_system(diagnostics: Res<Diagnostics>, mut query: Query<&mut Text,
   }
 }
 
+fn speed_update_system(
+  rigid_body_set: Res<RigidBodySet>,
+  mut text_query: Query<&mut Text, With<SpeedText>>,
+  player_query: Query<&RigidBodyHandleComponent, With<PlayerMarker>>,
+) {
+  for player in player_query.iter() {
+    // TODO: would be better to calculate this in a function in player somehow
+    let player_body = rigid_body_set.get(player.handle());
+    let player_velocity = player_body.unwrap().linvel();
+    let player_speed = Vec3::new(player_velocity.x, 0.0, player_velocity.z).length();
+
+    for mut text in text_query.iter_mut() {
+      text.value = format!("{} m/s", player_speed);
+    }
+  }
+}
+
 fn setup(commands: &mut Commands, asset_server: Res<AssetServer>) {
   commands
     // UI camera
     .spawn(CameraUiBundle::default())
-    // texture
+    // fps display
     .spawn(TextBundle {
       style: Style {
         align_self: AlignSelf::FlexEnd,
@@ -54,5 +74,30 @@ fn setup(commands: &mut Commands, asset_server: Res<AssetServer>) {
       },
       ..Default::default()
     })
-    .with(FpsText);
+    .with(FpsText)
+    // speed display
+    .spawn(TextBundle {
+      style: Style {
+        // TODO: dont know how to properly center this horizontally
+        align_self: AlignSelf::Center,
+        position_type: PositionType::Relative,
+        position: Rect {
+          top: Val::Px(50.0),
+          right: Val::Px(-480.0),
+          ..Default::default()
+        },
+        ..Default::default()
+      },
+      text: Text {
+        value: "speed".to_string(),
+        font: asset_server.load("fonts/FiraMono-Medium.ttf"),
+        style: TextStyle {
+          font_size: 16.0,
+          color: Color::rgba(1.0, 1.0, 1.0, 0.5),
+          ..Default::default()
+        },
+      },
+      ..Default::default()
+    })
+    .with(SpeedText);
 }

src/player.rs

@@ -21,7 +21,7 @@ impl Plugin for PlayerPlugin {
 }
 
 #[derive(Default)]
-struct PlayerMarker;
+pub struct PlayerMarker;
 
 #[derive(Default, Debug)]
 struct CameraData {