Rename velocity to speed (#19)

Velocity includes direction as well as magnitude, while these values
do not.

README.md

@@ -55,7 +55,7 @@ fn spawn_particle_system(mut commands: Commands, asset_server: Res<AssetServer>)
             max_particles: 10_000,
             default_sprite: asset_server.load("my_particle.png"),
             spawn_rate_per_second: 25.0.into(),
-            initial_velocity: JitteredValue::jittered(3.0, -1.0..1.0),
+            initial_speed: JitteredValue::jittered(3.0, -1.0..1.0),
             lifetime: JitteredValue::jittered(8.0, -2.0..2.0),
             color: ColorOverTime::Gradient(Gradient::new(vec![
                 ColorPoint::new(Color::WHITE, 0.0),

examples/basic.rs

@@ -38,7 +38,7 @@ fn startup_system(mut commands: Commands, asset_server: Res<AssetServer>) {
                 max_particles: 50_000,
                 default_sprite: asset_server.load("px.png"),
                 spawn_rate_per_second: 1000.0.into(),
-                initial_velocity: JitteredValue::jittered(3.0, -1.0..1.0),
+                initial_speed: JitteredValue::jittered(3.0, -1.0..1.0),
                 acceleration: ValueOverTime::Sin(SinWave {
                     amplitude: 150.0,
                     period: 5.0,

examples/local_space.rs

@@ -42,7 +42,7 @@ fn startup_system(mut commands: Commands, asset_server: Res<AssetServer>) {
                 emitter_angle: 0.0,
                 default_sprite: asset_server.load("px.png"),
                 spawn_rate_per_second: 35.0.into(),
-                initial_velocity: JitteredValue::jittered(25.0, 0.0..5.0),
+                initial_speed: JitteredValue::jittered(25.0, 0.0..5.0),
                 acceleration: 0.0.into(),
                 lifetime: JitteredValue::jittered(3.0, -2.0..2.0),
                 color: ColorOverTime::Gradient(Gradient::new(vec![
@@ -69,7 +69,7 @@ fn startup_system(mut commands: Commands, asset_server: Res<AssetServer>) {
                 emitter_angle: std::f32::consts::PI,
                 default_sprite: asset_server.load("px.png"),
                 spawn_rate_per_second: 35.0.into(),
-                initial_velocity: JitteredValue::jittered(25.0, 0.0..5.0),
+                initial_speed: JitteredValue::jittered(25.0, 0.0..5.0),
                 acceleration: 0.0.into(),
                 lifetime: JitteredValue::jittered(3.0, -2.0..2.0),
                 color: ColorOverTime::Gradient(Gradient::new(vec![

examples/time_scaling.rs

@@ -34,7 +34,7 @@ fn startup_system(mut commands: Commands, asset_server: Res<AssetServer>) {
                 emitter_angle: 0.0,
                 default_sprite: asset_server.load("px.png"),
                 spawn_rate_per_second: 35.0.into(),
-                initial_velocity: JitteredValue::jittered(25.0, 0.0..5.0),
+                initial_speed: JitteredValue::jittered(25.0, 0.0..5.0),
                 acceleration: 0.0.into(),
                 lifetime: JitteredValue::jittered(3.0, -2.0..2.0),
                 color: ColorOverTime::Gradient(Gradient::new(vec![
@@ -61,7 +61,7 @@ fn startup_system(mut commands: Commands, asset_server: Res<AssetServer>) {
                 emitter_angle: std::f32::consts::PI,
                 default_sprite: asset_server.load("px.png"),
                 spawn_rate_per_second: 35.0.into(),
-                initial_velocity: JitteredValue::jittered(25.0, 0.0..5.0),
+                initial_speed: JitteredValue::jittered(25.0, 0.0..5.0),
                 acceleration: 0.0.into(),
                 lifetime: JitteredValue::jittered(3.0, -2.0..2.0),
                 color: ColorOverTime::Gradient(Gradient::new(vec![

src/components.rs

@@ -81,14 +81,14 @@ pub struct ParticleSystem {
     /// Zero indicates straight to the right in the X direction. [`std::f32::consts::PI`] indicates straight left in the X direction.
     pub emitter_angle: f32,
 
-    /// The initial movement velocity of a particle.
+    /// The initial movement speed of a particle.
     ///
     /// This value can be constant, or have added jitter to have particles move at varying speeds.
-    pub initial_velocity: JitteredValue,
+    pub initial_speed: JitteredValue,
 
     /// The acceleration of each particle.
     ///
-    /// This value can change over time. Zero makes the particle move at its ``initial_velocity`` for its lifetime.
+    /// This value can change over time. Zero makes the particle move at its ``initial_speed`` for its lifetime.
     pub acceleration: ValueOverTime,
 
     /// The lifetime of each particle, in seconds.
@@ -146,7 +146,7 @@ impl Default for ParticleSystem {
             spawn_radius: 0.0.into(),
             emitter_shape: std::f32::consts::TAU,
             emitter_angle: 0.0,
-            initial_velocity: 1.0.into(),
+            initial_speed: 1.0.into(),
             acceleration: 0.0.into(),
             lifetime: 5.0.into(),
             color: ColorOverTime::default(),
@@ -205,9 +205,9 @@ pub struct Lifetime(pub f32);
 #[derive(Debug, Component, Default)]
 pub struct DistanceTraveled(pub f32);
 
-/// Defines the current velocity of an individual particle entity.
+/// Defines the current speed of an individual particle entity.
 #[derive(Debug, Component, Default)]
-pub struct Velocity(pub f32);
+pub struct Speed(pub f32);
 
 /// Defines the direction a particle is currently traveling.
 #[derive(Debug, Component, Default)]
@@ -298,7 +298,7 @@ pub struct ParticleSystemBundle {
 pub(crate) struct ParticleBundle {
     pub particle: Particle,
     pub lifetime: Lifetime,
-    pub velocity: Velocity,
+    pub speed: Speed,
     pub direction: Direction,
     pub distance: DistanceTraveled,
 }

src/lib.rs

@@ -41,7 +41,7 @@
 //!             max_particles: 10_000,
 //!             default_sprite: asset_server.load("my_particle.png"),
 //!             spawn_rate_per_second: 25.0.into(),
-//!             initial_velocity: JitteredValue::jittered(3.0, -1.0..1.0),
+//!             initial_speed: JitteredValue::jittered(3.0, -1.0..1.0),
 //!             lifetime: JitteredValue::jittered(8.0, -2.0..2.0),
 //!             color: ColorOverTime::Gradient(Gradient::new(vec![
 //!                 ColorPoint::new(Color::WHITE, 0.0),

src/systems.rs

@@ -9,7 +9,7 @@ use rand::prelude::*;
 use crate::{
     components::{
         BurstIndex, Direction, Lifetime, Particle, ParticleBundle, ParticleCount, ParticleSpace,
-        ParticleSystem, Playing, RunningState, Velocity,
+        ParticleSystem, Playing, RunningState, Speed,
     },
     values::ColorOverTime,
     DistanceTraveled,
@@ -137,9 +137,7 @@ pub fn partcle_spawner(
                                 max_lifetime: particle_system.lifetime.get_value(&mut rng),
                                 max_distance: particle_system.max_distance,
                             },
-                            velocity: Velocity(
-                                particle_system.initial_velocity.get_value(&mut rng),
-                            ),
+                            speed: Speed(particle_system.initial_speed.get_value(&mut rng)),
                             direction: Direction::new(
                                 direction,
                                 particle_system.z_value_override.is_some(),
@@ -165,9 +163,7 @@ pub fn partcle_spawner(
                                     max_lifetime: particle_system.lifetime.get_value(&mut rng),
                                     max_distance: particle_system.max_distance,
                                 },
-                                velocity: Velocity(
-                                    particle_system.initial_velocity.get_value(&mut rng),
-                                ),
+                                speed: Speed(particle_system.initial_speed.get_value(&mut rng)),
                                 direction: Direction::new(
                                     direction,
                                     particle_system.z_value_override.is_some(),
@@ -232,26 +228,26 @@ pub(crate) fn particle_transform(
         &Lifetime,
         &Direction,
         &mut DistanceTraveled,
-        &mut Velocity,
+        &mut Speed,
         &mut Transform,
     )>,
     particle_system_query: Query<&ParticleSystem>,
     time: Res<Time>,
 ) {
     particle_query.par_for_each_mut(
         512,
-        |(particle, lifetime, direction, mut distance, mut velocity, mut transform)| {
+        |(particle, lifetime, direction, mut distance, mut speed, mut transform)| {
             if let Ok(particle_system) = particle_system_query.get(particle.parent_system) {
                 let lifetime_pct = lifetime.0 / particle.max_lifetime;
                 let initial_position = transform.translation;
                 if particle_system.use_scaled_time {
-                    velocity.0 += particle_system.acceleration.at_lifetime_pct(lifetime_pct)
+                    speed.0 += particle_system.acceleration.at_lifetime_pct(lifetime_pct)
                         * time.delta_seconds();
-                    transform.translation += direction.0 * velocity.0 * time.delta_seconds();
+                    transform.translation += direction.0 * speed.0 * time.delta_seconds();
                 } else {
-                    velocity.0 += particle_system.acceleration.at_lifetime_pct(lifetime_pct)
+                    speed.0 += particle_system.acceleration.at_lifetime_pct(lifetime_pct)
                         * time.raw_delta_seconds();
-                    transform.translation += direction.0 * velocity.0 * time.raw_delta_seconds();
+                    transform.translation += direction.0 * speed.0 * time.raw_delta_seconds();
                 }
 
                 transform.scale = Vec3::splat(particle_system.scale.at_lifetime_pct(lifetime_pct));