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/*
https://raw.githubusercontent.com/hexops/mach/main/examples/boids/updateSprites.wgsl
*/
struct Particle {
pos : vec2<f32>,
vel : vec2<f32>,
};
struct SimParams {
deltaT : f32,
rule1Distance : f32,
rule2Distance : f32,
rule3Distance : f32,
rule1Scale : f32,
rule2Scale : f32,
rule3Scale : f32,
};
struct Particles {
particles : array<Particle>,
};
@binding(0) @group(0) var<uniform> params : SimParams;
@binding(1) @group(0) var<storage, read> particlesA : Particles;
@binding(2) @group(0) var<storage, read_write> particlesB : Particles;
// https://github.com/austinEng/Project6-Vulkan-Flocking/blob/master/data/shaders/computeparticles/particle.comp
@compute @workgroup_size(64)
fn main(@builtin(global_invocation_id) GlobalInvocationID : vec3<u32>) {
var index : u32 = GlobalInvocationID.x;
var vPos = particlesA.particles[index].pos;
var vVel = particlesA.particles[index].vel;
var cMass = vec2<f32>(0.0, 0.0);
var cVel = vec2<f32>(0.0, 0.0);
var colVel = vec2<f32>(0.0, 0.0);
var cMassCount : u32 = 0u;
var cVelCount : u32 = 0u;
var pos : vec2<f32>;
var vel : vec2<f32>;
for (var i : u32 = 0u; i < arrayLength(&particlesA.particles); i = i + 1u) {
if (i == index) {
continue;
}
pos = particlesA.particles[i].pos.xy;
vel = particlesA.particles[i].vel.xy;
if (distance(pos, vPos) < params.rule1Distance) {
cMass = cMass + pos;
cMassCount = cMassCount + 1u;
}
if (distance(pos, vPos) < params.rule2Distance) {
colVel = colVel - (pos - vPos);
}
if (distance(pos, vPos) < params.rule3Distance) {
cVel = cVel + vel;
cVelCount = cVelCount + 1u;
}
}
if (cMassCount > 0u) {
var temp = f32(cMassCount);
cMass = (cMass / vec2<f32>(temp, temp)) - vPos;
}
if (cVelCount > 0u) {
var temp = f32(cVelCount);
cVel = cVel / vec2<f32>(temp, temp);
}
vVel = vVel + (cMass * params.rule1Scale) + (colVel * params.rule2Scale) +
(cVel * params.rule3Scale);
// clamp velocity for a more pleasing simulation
vVel = normalize(vVel) * clamp(length(vVel), 0.0, 0.1);
// kinematic update
vPos = vPos + (vVel * params.deltaT);
// Wrap around boundary
if (vPos.x < -1.0) {
vPos.x = 1.0;
}
if (vPos.x > 1.0) {
vPos.x = -1.0;
}
if (vPos.y < -1.0) {
vPos.y = 1.0;
}
if (vPos.y > 1.0) {
vPos.y = -1.0;
}
// Write back
particlesB.particles[index].pos = vPos;
particlesB.particles[index].vel = vVel;
}
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