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change the ribbon example into a tracer example. #380

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change the ribbon example into a tracer example. #380

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4c21073
turn the ribbon example into a tracer example
naasblod Oct 15, 2024
b3de827
clean it up
naasblod Oct 15, 2024
8508ca1
clean up and better description
naasblod Oct 15, 2024
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42 changes: 29 additions & 13 deletions examples/ribbon.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
//! Draws a trail and connects the trails using a ribbon.

use bevy::color::palettes::css::YELLOW;
use bevy::math::vec4;
use bevy::prelude::*;
use bevy::{
Expand All @@ -18,7 +19,7 @@ const L: f32 = 0.384;

const TIME_SCALE: f32 = 10.0;
const SHAPE_SCALE: f32 = 25.0;
const LIFETIME: f32 = 2.5;
const LIFETIME: f32 = 1.5;
const TRAIL_SPAWN_RATE: f32 = 256.0;

fn main() -> Result<(), Box<dyn std::error::Error>> {
Expand Down Expand Up @@ -73,18 +74,12 @@ fn setup(mut commands: Commands, mut effects: ResMut<Assets<EffectAsset>>) {

let clone_modifier = CloneModifier::new(1.0 / TRAIL_SPAWN_RATE, 1);

let time = writer.time().mul(writer.lit(TIME_SCALE));
let pos = writer.add_property("head_pos", Vec3::ZERO.into());
let pos = writer.prop(pos);

let move_modifier = SetAttributeModifier {
attribute: Attribute::POSITION,
value: (WriterExpr::vec3(
writer.lit(1.0 - K).mul(time.clone().cos())
+ writer.lit(L * K) * (writer.lit((1.0 - K) / K) * time.clone()).cos(),
writer.lit(1.0 - K).mul(time.clone().sin())
- writer.lit(L * K) * (writer.lit((1.0 - K) / K) * time.clone()).sin(),
writer.lit(0.0),
) * writer.lit(SHAPE_SCALE))
.expr(),
value: pos.expr(),
};

let update_lifetime_attr = SetAttributeModifier {
Expand All @@ -111,6 +106,10 @@ fn setup(mut commands: Commands, mut effects: ResMut<Assets<EffectAsset>>) {
.update_groups(move_modifier, ParticleGroupSet::single(0))
.update_groups(clone_modifier, ParticleGroupSet::single(0))
.update_groups(update_lifetime_attr, ParticleGroupSet::single(1))
.render(SizeOverLifetimeModifier {
gradient: Gradient::linear(Vec2::ONE, Vec2::ZERO),
..default()
})
.render(RibbonModifier)
.render_groups(render_color, ParticleGroupSet::single(1));

Expand All @@ -125,9 +124,26 @@ fn setup(mut commands: Commands, mut effects: ResMut<Assets<EffectAsset>>) {
.insert(Name::new("ribbon"));
}

fn move_particle_effect(mut query: Query<&mut Transform, With<ParticleEffect>>, timer: Res<Time>) {
let theta = timer.elapsed_seconds() * 1.0;
fn move_particle_effect(
mut gizmos: Gizmos,
mut query: Query<&mut Transform, With<ParticleEffect>>,
mut effect: Query<&mut EffectProperties>,
timer: Res<Time>,
) {
let Ok(mut properties) = effect.get_single_mut() else {
return;
};
for mut transform in query.iter_mut() {
transform.translation = vec3(f32::cos(theta), f32::sin(theta), 0.0) * 5.0;
let time = timer.elapsed_seconds() * TIME_SCALE;
let pos = vec3(
(1.0 - K) * (time.clone().cos()) + (L * K) * (((1.0 - K) / K) * time.clone()).cos(),
(1.0 - K) * (time.clone().sin()) - (L * K) * (((1.0 - K) / K) * time.clone()).sin(),
0.0,
) * SHAPE_SCALE;

//let pos = vec3(f32::cos(theta), f32::sin(theta), 0.0) * 5.0;
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properties.set("head_pos", (pos).into());
gizmos.sphere(pos, Quat::IDENTITY, 1.0, YELLOW);
transform.translation = pos;
}
}
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