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static const std::string COMPUTE_SHADER_CODE = R"(
#version 430
layout (local_size_x = 1) in;
layout (std430, binding=1) buffer bufferA{ float data[]; };
uniform vec2 world;
// ODE solver
vec2 f(vec2); // field definition is to be appended
vec2 explicitEuler(float h, vec2 v) {
return v + h * f(v);
}
vec2 classicalRungeKutta(float h, vec2 v) {
const vec2 k1 = f(v);
const vec2 k2 = f(v + h/2. * k1);
const vec2 k3 = f(v + h/2. * k2);
const vec2 k4 = f(v + h * k3);
return v + h * (1./6.*k1 + 1./3.*k2 + 1./3.*k3 + 1./6.*k4);
}
// pseudo random numbers for particle placement
float rand(vec2 v){
return fract(sin(dot(v, vec2(12.9898,78.233))) * 43758.5453);
}
float mapUnitToWorldX(float s) {
return -(world.x/2.) + s * world.x;
}
float mapUnitToWorldY(float s) {
return -(world.y/2.) + s * world.y;
}
bool insideWorld(vec2 v) {
return v.x > -world.x/2.
&& v.x < world.x/2.
&& v.y > -world.y/2.
&& v.y < world.y/2.;
}
void main() {
const uint i = 3*gl_GlobalInvocationID.x;
const vec2 v = vec2(data[i+0], data[i+1]);
const vec2 w = classicalRungeKutta(0.01, v);
if ( data[i+2] < 5. && insideWorld(v) ) {
data[i+0] = w.x;
data[i+1] = w.y;
data[i+2] += 0.01;
} else {
data[i+0] = mapUnitToWorldX(rand(v));
data[i+1] = mapUnitToWorldY(rand(w));
data[i+2] = rand(v+w) * 5.;
}
}
)";
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