2018-soft-3d-renderer/src/light.cpp

#include "camera.h"
#include "color.h"
#include "light.h"


// PUBLIC FUNCTIONS
ColorF32 ComputeLight(
        Point &position, Vector &normal, Material &material, Light &light, Camera &camera)
{
    // Point light intensity is a function of the falloff factors and the distance
    Vector direction = light.position - position;
    VectorNormalize(direction);
    float distance = VectorLength(direction);

    ColorF32 intensity =
        (light.intensity * light.color)
        / (light.falloffConstant + (light.falloffLinear * distance));


    // Diffuse Light = Kr * I * (alpha + (1 - alpha) * n.d)
    float dotNormalDirection = MAX(VectorDot(normal, direction), 0.0f);
    float alpha = 0.2f;

    ColorF32 diffuseLight =
        material.diffuse
        * intensity
        * (alpha + (1.0f - alpha) * dotNormalDirection);


    // Specular Light = Ks * I * (r.v)^sp
    Vector view = camera.position - position;
    VectorNormalize(view);
    Vector reflection = (2.0f * dotNormalDirection * normal) - direction;
    float dotReflectionView = MAX(VectorDot(reflection, view), 0.0f);

    ColorF32 specularLight =
        material.specular
        * intensity
        * powf(dotReflectionView, material.glossiness);


    // Total light is sum of all lights
    ColorF32 result = diffuseLight + specularLight;


    return result;
}