let mut glfw_ctx = GlfwContext::new(900, 700)?;

init(Config::default())?;

let surface = glfw_ctx.create_surface(900, 700)?;

let graphics = graphics_create(surface, 900, 700, TextureFormat::Rgba16Float)?;

graphics_mode_3d(graphics)?;

transform_set_position(graphics, Vec3::new(0.0, 4.0, 14.0))?;

transform_look_at(graphics, Vec3::new(0.0, 0.0, 0.0))?;

let sphere = geometry_sphere(0.08, 8, 6)?;

let capacity: u32 = 2000;

let position_attr = geometry_attribute_position();

let color_attr = geometry_attribute_color();

let p = particles_create(capacity, vec![position_attr, color_attr])?;

let position_buf =

particles_buffer(p, position_attr)?.ok_or(error::ProcessingError::ParticlesNotFound)?;

let color_buf =

particles_buffer(p, color_attr)?.ok_or(error::ProcessingError::ParticlesNotFound)?;

// push unemitted slots off-screen so they don't render at the origin

let init_positions: Vec<f32> = (0..capacity * 3).map(|_| 1.0e6).collect();

buffer_write(

position_buf,

init_positions

.iter()

.flat_map(|f| f.to_le_bytes())

.collect(),

)?;

let mat = {

let m = material_create_unlit()?;

material_set_albedo_buffer(m, color_buf)?;

m

};

let mut frame: u32 = 0;

while glfw_ctx.poll_events() {

graphics_begin_draw(graphics)?;

graphics_record_command(

graphics,

DrawCommand::BackgroundColor(bevy::color::Color::srgb(0.06, 0.06, 0.08)),

)?;

graphics_record_command(graphics, DrawCommand::Material(mat))?;

graphics_record_command(

graphics,

DrawCommand::Particles {

particles: p,

geometry: sphere,

},

)?;

graphics_end_draw(graphics)?;

let burst = 4u32;

let mut positions: Vec<f32> = Vec::with_capacity(burst as usize * 3);

let mut colors: Vec<f32> = Vec::with_capacity(burst as usize * 4);

for k in 0..burst {

let i = frame * burst + k;

let t = i as f32 * 0.05;

let radius = 1.5 + (t * 0.02).min(3.0);

let height = ((t * 0.1).sin()) * 2.0;

positions.push(t.cos() * radius);

positions.push(height);

positions.push(t.sin() * radius);

let h = (i as f32 * 0.012) % 1.0;

let (r, g, b) = hsv_to_rgb(h, 0.85, 1.0);

colors.push(r);

colors.push(g);

colors.push(b);

colors.push(1.0);

}

let position_bytes: Vec<u8> = positions.iter().flat_map(|f| f.to_le_bytes()).collect();

let color_bytes: Vec<u8> = colors.iter().flat_map(|f| f.to_le_bytes()).collect();

particles_emit(

p,

burst,

vec![(position_attr, position_bytes), (color_attr, color_bytes)],

)?;

frame += 1;

}

Ok(())

let i = (h * 6.0).floor();

let f = h * 6.0 - i;

let p = v * (1.0 - s);

let q = v * (1.0 - f * s);

let t = v * (1.0 - (1.0 - f) * s);

match (i as i32) % 6 {

0 => (v, t, p),

1 => (q, v, p),

2 => (p, v, t),

3 => (p, q, v),

4 => (t, p, v),

_ => (v, p, q),

}