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Improve first person camera in example (#15109)
# Objective - I've seen quite a few people on discord copy-paste the camera code of the first-person example and then run into problems with the pitch. - ~~Additionally, the code is framerate-dependent.~~ it's not, see comment in PR ## Solution - Make the code good enough to be copy-pasteable - ~~Use `dt` to make the code framerate-independent~~ Add comment explaining why we don't use `dt` - Clamp the pitch - Move the camera sensitivity into a component for better configurability ## Testing Didn't run the example again, but the code is straight from another project I have open, so I'm not worried. --------- Co-authored-by: Antony <antony.m.3012@gmail.com>
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1 changed files with 48 additions and 8 deletions
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@ -42,6 +42,8 @@
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//! | arrow up | Decrease FOV |
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//! | arrow down | Increase FOV |
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use std::f32::consts::FRAC_PI_2;
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use bevy::color::palettes::tailwind;
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use bevy::input::mouse::AccumulatedMouseMotion;
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use bevy::pbr::NotShadowCaster;
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@ -67,6 +69,22 @@ fn main() {
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#[derive(Debug, Component)]
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struct Player;
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#[derive(Debug, Component, Deref, DerefMut)]
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struct CameraSensitivity(Vec2);
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impl Default for CameraSensitivity {
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fn default() -> Self {
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Self(
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// These factors are just arbitrary mouse sensitivity values.
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// It's often nicer to have a faster horizontal sensitivity than vertical.
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// We use a component for them so that we can make them user-configurable at runtime
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// for accessibility reasons.
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// It also allows you to inspect them in an editor if you `Reflect` the component.
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Vec2::new(0.003, 0.002),
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)
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}
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}
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#[derive(Debug, Component)]
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struct WorldModelCamera;
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@ -90,6 +108,7 @@ fn spawn_view_model(
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commands
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.spawn((
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Player,
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CameraSensitivity::default(),
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SpatialBundle {
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transform: Transform::from_xyz(0.0, 1.0, 0.0),
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..default()
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@ -220,17 +239,36 @@ fn spawn_text(mut commands: Commands) {
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fn move_player(
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accumulated_mouse_motion: Res<AccumulatedMouseMotion>,
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mut player: Query<&mut Transform, With<Player>>,
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mut player: Query<(&mut Transform, &CameraSensitivity), With<Player>>,
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) {
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let mut transform = player.single_mut();
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let Ok((mut transform, camera_sensitivity)) = player.get_single_mut() else {
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return;
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};
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let delta = accumulated_mouse_motion.delta;
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if delta != Vec2::ZERO {
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let yaw = -delta.x * 0.003;
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let pitch = -delta.y * 0.002;
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// Order of rotations is important, see <https://gamedev.stackexchange.com/a/136175/103059>
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transform.rotate_y(yaw);
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transform.rotate_local_x(pitch);
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// Note that we are not multiplying by delta_time here.
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// The reason is that for mouse movement, we already get the full movement that happened since the last frame.
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// This means that if we multiply by delta_time, we will get a smaller rotation than intended by the user.
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// This situation is reversed when reading e.g. analog input from a gamepad however, where the same rules
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// as for keyboard input apply. Such an input should be multiplied by delta_time to get the intended rotation
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// independent of the framerate.
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let delta_yaw = -delta.x * camera_sensitivity.x;
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let delta_pitch = -delta.y * camera_sensitivity.y;
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let (yaw, pitch, roll) = transform.rotation.to_euler(EulerRot::YXZ);
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let yaw = yaw + delta_yaw;
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// If the pitch was ±¹⁄₂ π, the camera would look straight up or down.
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// When the user wants to move the camera back to the horizon, which way should the camera face?
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// The camera has no way of knowing what direction was "forward" before landing in that extreme position,
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// so the direction picked will for all intents and purposes be arbitrary.
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// Another issue is that for mathematical reasons, the yaw will effectively be flipped when the pitch is at the extremes.
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// To not run into these issues, we clamp the pitch to a safe range.
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const PITCH_LIMIT: f32 = FRAC_PI_2 - 0.01;
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let pitch = (pitch + delta_pitch).clamp(-PITCH_LIMIT, PITCH_LIMIT);
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transform.rotation = Quat::from_euler(EulerRot::YXZ, yaw, pitch, roll);
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}
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}
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@ -238,7 +276,9 @@ fn change_fov(
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input: Res<ButtonInput<KeyCode>>,
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mut world_model_projection: Query<&mut Projection, With<WorldModelCamera>>,
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) {
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let mut projection = world_model_projection.single_mut();
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let Ok(mut projection) = world_model_projection.get_single_mut() else {
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return;
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};
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let Projection::Perspective(ref mut perspective) = projection.as_mut() else {
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unreachable!(
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"The `Projection` component was explicitly built with `Projection::Perspective`"
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