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// Copyright 2020 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// vertex shader
[[stage(vertex)]]
fn vert_main([[location(0)]] a_particlePos : vec2<f32>,
[[location(1)]] a_particleVel : vec2<f32>,
[[location(2)]] a_pos : vec2<f32>)
-> [[builtin(position)]] vec4<f32> {
var angle : f32 = -atan2(a_particleVel.x, a_particleVel.y);
var pos : vec2<f32> = vec2<f32>(
(a_pos.x * cos(angle)) - (a_pos.y * sin(angle)),
(a_pos.x * sin(angle)) + (a_pos.y * cos(angle)));
return vec4<f32>(pos + a_particlePos, 0.0, 1.0);
}
// fragment shader
[[stage(fragment)]]
fn frag_main() -> [[location(0)]] vec4<f32> {
return vec4<f32>(1.0, 1.0, 1.0, 1.0);
}
// compute shader
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, 5>;
};
[[binding(0), group(0)]] var<uniform> params : SimParams;
[[binding(1), group(0)]] var<storage, read_write> 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
[[stage(compute), workgroup_size(1)]]
fn comp_main(
[[builtin(global_invocation_id)]] gl_GlobalInvocationID : vec3<u32>) {
var index : u32 = gl_GlobalInvocationID.x;
if (index >= 5u) {
return;
}
var vPos : vec2<f32> = particlesA.particles[index].pos;
var vVel : vec2<f32> = particlesA.particles[index].vel;
var cMass : vec2<f32> = vec2<f32>(0.0, 0.0);
var cVel : vec2<f32> = vec2<f32>(0.0, 0.0);
var colVel : vec2<f32> = vec2<f32>(0.0, 0.0);
var cMassCount : i32 = 0;
var cVelCount : i32 = 0;
var pos : vec2<f32>;
var vel : vec2<f32>;
for(var i : u32 = 0u; i < 5u; 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 + 1;
}
if (distance(pos, vPos) < params.rule2Distance) {
colVel = colVel - (pos - vPos);
}
if (distance(pos, vPos) < params.rule3Distance) {
cVel = cVel + vel;
cVelCount = cVelCount + 1;
}
}
if (cMassCount > 0) {
cMass =
(cMass / vec2<f32>(f32(cMassCount), f32(cMassCount))) - vPos;
}
if (cVelCount > 0) {
cVel = cVel / vec2<f32>(f32(cVelCount), f32(cVelCount));
}
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;
}