shadow_biases: Support moving the light position and resetting biases (#10185)

# Objective

- Make it possible to move the light position around in the
`shadow_biases` example
- Also support resetting the depth/normal biases to the engine defaults,
or zero.

## Solution

- The light position is displayed in the text overlay.
- The light position can be adjusted with
left/right/up/down/pgup/pgdown.
- The depth/normal biases can be reset to defaults by pressing R, or to
zero by pressing Z.

---------

Co-authored-by: robtfm <50659922+robtfm@users.noreply.github.com>

examples/3d/shadow_biases.rs

@@ -12,6 +12,7 @@ fn main() {
             Update,
             (
                 cycle_filter_methods,
+                adjust_light_position,
                 adjust_point_light_biases,
                 toggle_light,
                 adjust_directional_light_biases,
@@ -21,6 +22,9 @@ fn main() {
         .run();
 }
 
+#[derive(Component)]
+struct Lights;
+
 /// set up a 3D scene to test shadow biases and perspective projections
 fn setup(
     mut commands: Commands,
@@ -44,8 +48,17 @@ fn setup(
         .unwrap(),
     );
 
-    commands.spawn(PointLightBundle {
-        transform: Transform::from_xyz(5.0, 5.0, 0.0),
+    let light_transform = Transform::from_xyz(5.0, 5.0, 0.0).looking_at(Vec3::ZERO, Vec3::Y);
+    commands
+        .spawn((
+            SpatialBundle {
+                transform: light_transform,
+                ..default()
+            },
+            Lights,
+        ))
+        .with_children(|builder| {
+            builder.spawn(PointLightBundle {
                 point_light: PointLight {
                     intensity: 0.0,
                     range: spawn_plane_depth,
@@ -57,8 +70,7 @@ fn setup(
                 },
                 ..default()
             });
-
-    commands.spawn(DirectionalLightBundle {
+            builder.spawn(DirectionalLightBundle {
                 directional_light: DirectionalLight {
                     illuminance: 100000.0,
                     shadow_depth_bias: 0.0,
@@ -66,14 +78,9 @@ fn setup(
                     shadows_enabled: true,
                     ..default()
                 },
-        transform: Transform::from_rotation(Quat::from_euler(
-            EulerRot::ZYX,
-            0.0,
-            PI / 2.,
-            -PI / 4.,
-        )),
                 ..default()
             });
+        });
 
     // camera
     commands.spawn((
@@ -90,7 +97,15 @@ fn setup(
         commands.spawn(PbrBundle {
             mesh: sphere_handle.clone(),
             material: white_handle.clone(),
-            transform: Transform::from_xyz(0.0, spawn_height, z_i32 as f32),
+            transform: Transform::from_xyz(
+                0.0,
+                if z_i32 % 4 == 0 {
+                    spawn_height
+                } else {
+                    sphere_radius
+                },
+                z_i32 as f32,
+            ),
             ..default()
         });
     }
@@ -106,18 +121,33 @@ fn setup(
         font_size: 20.,
         ..default()
     };
-    commands.spawn(
-        TextBundle::from_sections([
+    commands
+        .spawn(NodeBundle {
+            style: Style {
+                position_type: PositionType::Absolute,
+                padding: UiRect::all(Val::Px(5.0)),
+                ..default()
+            },
+            z_index: ZIndex::Global(i32::MAX),
+            background_color: Color::BLACK.with_a(0.75).into(),
+            ..default()
+        })
+        .with_children(|c| {
+            c.spawn(TextBundle::from_sections([
                 TextSection::new("Controls:\n", style.clone()),
                 TextSection::new("WSAD  - forward/back/strafe left/right\n", style.clone()),
                 TextSection::new("E / Q - up / down\n", style.clone()),
+                TextSection::new("R / Z - reset biases to default / zero\n", style.clone()),
                 TextSection::new(
                     "L     - switch between directional and point lights [",
                     style.clone(),
                 ),
                 TextSection::new("DirectionalLight", style.clone()),
                 TextSection::new("]\n", style.clone()),
-            TextSection::new("F     - switch between filter methods [", style.clone()),
+                TextSection::new(
+                    "F     - switch directional light filter methods [",
+                    style.clone(),
+                ),
                 TextSection::new("Hardware2x2", style.clone()),
                 TextSection::new("]\n", style.clone()),
                 TextSection::new("1/2   - change point light depth bias [", style.clone()),
@@ -135,14 +165,25 @@ fn setup(
                 ),
                 TextSection::new("0.0", style.clone()),
                 TextSection::new("]\n", style.clone()),
-        ])
-        .with_style(Style {
-            position_type: PositionType::Absolute,
-            top: Val::Px(12.0),
-            left: Val::Px(12.0),
-            ..default()
-        }),
-    );
+                TextSection::new(
+                    "left/right/up/down/pgup/pgdown - adjust light position (looking at 0,0,0) [",
+                    style.clone(),
+                ),
+                TextSection::new(
+                    format!("{:.1},", light_transform.translation.x),
+                    style.clone(),
+                ),
+                TextSection::new(
+                    format!(" {:.1},", light_transform.translation.y),
+                    style.clone(),
+                ),
+                TextSection::new(
+                    format!(" {:.1}", light_transform.translation.z),
+                    style.clone(),
+                ),
+                TextSection::new("]\n", style.clone()),
+            ]));
+        });
 }
 
 fn toggle_light(
@@ -154,7 +195,7 @@ fn toggle_light(
     if input.just_pressed(KeyCode::L) {
         for mut light in &mut point_lights {
             light.intensity = if light.intensity == 0.0 {
-                example_text.single_mut().sections[4].value = "PointLight".to_string();
+                example_text.single_mut().sections[5].value = "PointLight".to_string();
                 100000000.0
             } else {
                 0.0
@@ -162,7 +203,7 @@ fn toggle_light(
         }
         for mut light in &mut directional_lights {
             light.illuminance = if light.illuminance == 0.0 {
-                example_text.single_mut().sections[4].value = "DirectionalLight".to_string();
+                example_text.single_mut().sections[5].value = "DirectionalLight".to_string();
                 100000.0
             } else {
                 0.0
@@ -171,6 +212,42 @@ fn toggle_light(
     }
 }
 
+fn adjust_light_position(
+    input: Res<Input<KeyCode>>,
+    mut lights: Query<&mut Transform, With<Lights>>,
+    mut example_text: Query<&mut Text>,
+) {
+    let mut offset = Vec3::ZERO;
+    if input.just_pressed(KeyCode::Left) {
+        offset.x -= 1.0;
+    }
+    if input.just_pressed(KeyCode::Right) {
+        offset.x += 1.0;
+    }
+    if input.just_pressed(KeyCode::Up) {
+        offset.z -= 1.0;
+    }
+    if input.just_pressed(KeyCode::Down) {
+        offset.z += 1.0;
+    }
+    if input.just_pressed(KeyCode::PageDown) {
+        offset.y -= 1.0;
+    }
+    if input.just_pressed(KeyCode::PageUp) {
+        offset.y += 1.0;
+    }
+    if offset != Vec3::ZERO {
+        let mut example_text = example_text.single_mut();
+        for mut light in &mut lights {
+            light.translation += offset;
+            light.look_at(Vec3::ZERO, Vec3::Y);
+            example_text.sections[23].value = format!("{:.1},", light.translation.x);
+            example_text.sections[24].value = format!(" {:.1},", light.translation.y);
+            example_text.sections[25].value = format!(" {:.1}", light.translation.z);
+        }
+    }
+}
+
 fn cycle_filter_methods(
     input: Res<Input<KeyCode>>,
     mut filter_methods: Query<&mut ShadowFilteringMethod>,
@@ -193,7 +270,7 @@ fn cycle_filter_methods(
                     ShadowFilteringMethod::Hardware2x2
                 }
             };
-            example_text.single_mut().sections[7].value = filter_method_string;
+            example_text.single_mut().sections[8].value = filter_method_string;
         }
     }
 }
@@ -208,24 +285,27 @@ fn adjust_point_light_biases(
     for mut light in &mut query {
         if input.just_pressed(KeyCode::Key1) {
             light.shadow_depth_bias -= depth_bias_step_size;
-            example_text.single_mut().sections[10].value =
-                format!("{:.2}", light.shadow_depth_bias);
         }
         if input.just_pressed(KeyCode::Key2) {
             light.shadow_depth_bias += depth_bias_step_size;
-            example_text.single_mut().sections[10].value =
-                format!("{:.2}", light.shadow_depth_bias);
         }
         if input.just_pressed(KeyCode::Key3) {
             light.shadow_normal_bias -= normal_bias_step_size;
-            example_text.single_mut().sections[13].value =
-                format!("{:.1}", light.shadow_normal_bias);
         }
         if input.just_pressed(KeyCode::Key4) {
             light.shadow_normal_bias += normal_bias_step_size;
-            example_text.single_mut().sections[13].value =
-                format!("{:.1}", light.shadow_normal_bias);
         }
+        if input.just_pressed(KeyCode::R) {
+            light.shadow_depth_bias = PointLight::DEFAULT_SHADOW_DEPTH_BIAS;
+            light.shadow_normal_bias = PointLight::DEFAULT_SHADOW_NORMAL_BIAS;
+        }
+        if input.just_pressed(KeyCode::Z) {
+            light.shadow_depth_bias = 0.0;
+            light.shadow_normal_bias = 0.0;
+        }
+
+        example_text.single_mut().sections[11].value = format!("{:.2}", light.shadow_depth_bias);
+        example_text.single_mut().sections[14].value = format!("{:.1}", light.shadow_normal_bias);
     }
 }
 
@@ -239,24 +319,27 @@ fn adjust_directional_light_biases(
     for mut light in &mut query {
         if input.just_pressed(KeyCode::Key5) {
             light.shadow_depth_bias -= depth_bias_step_size;
-            example_text.single_mut().sections[16].value =
-                format!("{:.2}", light.shadow_depth_bias);
         }
         if input.just_pressed(KeyCode::Key6) {
             light.shadow_depth_bias += depth_bias_step_size;
-            example_text.single_mut().sections[16].value =
-                format!("{:.2}", light.shadow_depth_bias);
         }
         if input.just_pressed(KeyCode::Key7) {
             light.shadow_normal_bias -= normal_bias_step_size;
-            example_text.single_mut().sections[19].value =
-                format!("{:.1}", light.shadow_normal_bias);
         }
         if input.just_pressed(KeyCode::Key8) {
             light.shadow_normal_bias += normal_bias_step_size;
-            example_text.single_mut().sections[19].value =
-                format!("{:.1}", light.shadow_normal_bias);
         }
+        if input.just_pressed(KeyCode::R) {
+            light.shadow_depth_bias = DirectionalLight::DEFAULT_SHADOW_DEPTH_BIAS;
+            light.shadow_normal_bias = DirectionalLight::DEFAULT_SHADOW_NORMAL_BIAS;
+        }
+        if input.just_pressed(KeyCode::Z) {
+            light.shadow_depth_bias = 0.0;
+            light.shadow_normal_bias = 0.0;
+        }
+
+        example_text.single_mut().sections[17].value = format!("{:.2}", light.shadow_depth_bias);
+        example_text.single_mut().sections[20].value = format!("{:.1}", light.shadow_normal_bias);
     }
 }