cloudy-raytracer/shader/cloudshader.h

#ifndef CG1_TRACER_CLOUDSHADER_H
#define CG1_TRACER_CLOUDSHADER_H

#include "scene/scene.h"
#include "shader.h"
#include "light/light.h"
#include "primitive/primitive.h"
#include "common/noise/worleynoise.h"

float const TRANSMITTANCE_BREAK = 0.0001f;  // If transmittance goes below this limit, the cloud is considered opaque

struct CloudSettings
{
    int noiseSize = 256; // 64
    unsigned int seed = 0;  // 0 for random seed
    float densitySteps = .2f;   // .2f
    float scale = 30;   // 30
    float densityOffset = -.55f;    // -.55f
    float densityIntensity = 5.0f;  // 5.0f
    float darknessThreshold = .1f;  // .1f
    float shadowIntensity = .6f;    // .6f
    float shadowLightAbsorption = 1;    // 1
    float lightAbsorptionTowardsLight = 0.1f;   // .3f  // How Bright should the clouds be? Lower is brighter
    float lightAbsorptionThroughCloud = .8f;   // .8f   // How dark should the background be where the cloud is? Higher values mean darker background
    float phaseA = .8f; // .5f
    float phaseB = .4f; // .3f
    float phaseOffset = .8f;    // .8f
    float phaseIntensity = .1f;    // 1.0f
    float edgeFadeOffDistance = .5f;    // .5f
};

class CloudShader : public Shader
{
public:
    CloudShader(CloudSettings const &settings = CloudSettings());

    // Shader functions
    Color shade(Scene const &scene, Ray const &ray) const;

    Color transparency(const Scene &scene, const Ray &ray, float maxLength) const override;

private:
    CloudSettings settings;


    bool isTransparent() const;

    Noise cloudNoise;

    float getCloudDensity(Vector3d point, const Primitive *primitive = nullptr) const;

    Color lightMarch(const Scene &scene, Vector3d currentInCloudPosition, Vector3d lengthDistance,
                     const Primitive *cloudObject) const;

    float rayDensity(const Ray &ray, float maxLength) const;

    float phase(Vector3d visualRay, Vector3d illuminationRay) const;

    static float calcDualHenyeyGreenstein(float cosTheta, float g) ;

    static float calcBeer(float d) ;

    float getEdgeDensity(const Vector3d &point, const Primitive *primitive) const;
};


#endif //CG1_TRACER_CLOUDSHADER_H