FluidMath.h

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#pragma once
 
#include <glm/glm.hpp>
 
#include <cmath>
 
namespace eve::fluids {
 
struct FluidParams {
    float particleRadius = 0.05f;
    float supportRadius = 0.20f;
    float restDensity = 1.0f;
    glm::vec3 gravity{0.f, -9.8f, 0.f};
    float viscosity = 0.02f;
    float yieldStress = 0.0f;
    float cohesion = 0.0f;
    float adhesion = 0.0f;
    float damping = 0.0f;
    float maxVelocity = 20.f;
    int iterations = 1;
    int pbfIterations = 2;
};
 
struct FluidParticle {
    glm::vec3 pos{0.f};
    glm::vec3 vel{0.f};
};
 
inline float fluidPoly6(float r2, float h) {
    float h2 = h * h;
    if (r2 >= h2 || r2 <= 0.f) return 0.f;
    float q = h2 - r2;
    return 315.f / (64.f * 3.14159265358979f * std::pow(h, 9.f)) * q * q * q;
}
 
inline glm::vec3 fluidSpikyGrad(const glm::vec3& dx, float h) {
    float r2 = glm::dot(dx, dx);
    if (r2 >= h * h || r2 <= 1e-12f) return glm::vec3(0.f);
    float r = std::sqrt(r2);
    float q = h - r;
    float k = -45.f / (3.14159265358979f * std::pow(h, 6.f));
    return dx * (k * q * q / r);
}
 
inline float fluidViscLaplacian(float r, float h) {
    if (r >= h || r <= 1e-9f) return 0.f;
    return 45.f / (3.14159265358979f * std::pow(h, 6.f)) * (1.f - r / h);
}
 
inline float fluidCohesionKernel(float r, float h) {
    if (r >= h || r <= 1e-9f) return 0.f;
    const float q = h - r;
    return 32.f / (3.14159265358979f * std::pow(h, 9.f)) * q * q * q * r * r * r;
}
 
inline glm::vec3 fluidClampSpeed(const glm::vec3& v, float maxSpeed) {
    float s = glm::length(v);
    if (s > maxSpeed && s > 1e-9f) return v * (maxSpeed / s);
    return v;
}
 
}  // namespace eve::fluids