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"

int const NOISE_SIZE = 128;
float const TRANSMITTANCE_BREAK = 0.005f;  // If transmittance goes below this limit, the cloud is considered opaque

struct CloudSettings
{
    int densitySamples = 100;
    int lightSamples = 100;
    float scale = 10;
    float densityOffset = -0.57f;
    float densityIntensity = 7.0f;
    float darknessThreshold = 0.07f;
    float shadowIntensity = 0.8f;
    float shadowLightAbsorption = 1;
    float lightAbsorptionTowardsLight = 0.94f;
    float lightAbsorptionThroughCloud = 0.85f;
};

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;

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

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

    float scatterFactor(Vector3d visualRay, Vector3d illuminationRay) const;

    float HenyeyGreenstein(float cosTheta, float g) const;
};


#endif //CG1_TRACER_CLOUDSHADER_H