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#include "pathtracer.h"

using namespace CGLA;

path_tracer::path_tracer(int w, int h, bool explicit_direct, int subsamples)

: tracer(w, h)

{

    explicit_direct_ = explicit_direct;

    subsamples_ = subsamples;

}

CGLA::Vec3f path_tracer::trace(const ray& r, bool include_emitted)

{

    //intersect ray with

    hit_info hi;

    bool hit = scene_->intersect(r, hi);

    if (!hit)

        return Vec3f(0.f, 0.f, 0.f);

    //Vec3f x, y, z = hi.shading_normal;

    //orthogonal(z, x, y);

    //return (Vec3f(hi.texcoords(0),hi.texcoords(1),0) + Vec3f(0.f)) / 1.f;

    //only include emitted light if requested

    CGLA::Vec3f Le(0.f);

    if (include_emitted)

        Le = hi.emitted;

    //compute reflectance for each bsdf component

    float rho_diffuse = intensity(hi.diffuse);

    float rho_glossy = intensity(hi.glossy);

    float rho_reflection = intensity(hi.reflection);

    float rho_refraction = intensity(hi.refraction);

    float rho_total = rho_diffuse+rho_glossy+rho_reflection+rho_refraction;

    assert(rho_total < 1.f);

    if (rho_total == 0.f)

        return Le;

    //compute direct lighting on hit point

    CGLA::Vec3f Ld(0.f);

    Vec3f wo = -r.direction;

    if (explicit_direct_ && rho_diffuse+rho_glossy>0.f)

    {

        size_t nlums = scene_->luminaires();

        for (size_t i=0; i<nlums; ++i)

        {

            const luminaire* lum = scene_->get_luminaire(i);

            int samples = lum->samples();

            Vec3f L(0.f);

            for (int j=0; j<samples; ++j)

            {

                Vec3f Li, wi;

                if (lum->sample(r, hi, Li, wi))

                {

                    float cost = std::max(dot(hi.shading_normal, wi),0.f);

                    L += Li * cost * bsdf_evaluate(hi, wi, wo);

                }

                Ld += L / float(samples);

            }

        }

    }

    //use russian roulette to terminate path

    float prussian = 1.f;

    float rr = mt_random();

    if (r.depth > 3)

    {

        prussian = rho_total;

        if (rr >= prussian)

            return Ld + Le;

    }

    //figure out which bXdf to sample

    float pdiffuse = rho_diffuse/rho_total;

    float pglossy = rho_glossy/rho_total;

    float preflection = rho_reflection/rho_total;

    float prefraction = rho_refraction/rho_total;

    Vec3f wi;

    float pwi;

    Vec3f fs;

    bool sample_emitted = !explicit_direct_;

    if (rr <= pdiffuse)

    {

        //sample diffuse

        float pwi = sample_lambertian(hi, wo, wi);

        fs = lambertian_brdf(hi, wi, wo) / (pwi * pdiffuse * prussian);

    }

    else if (rr <= pdiffuse+pglossy)

    {

        //sample glossy part

        float pwi = sample_phong(hi, wo, wi);

        if (dot(hi.shading_normal, wi) <= 0.f)

            return Le + Ld;

        fs = phong_brdf(hi, wi, wo) / (pwi * pglossy * prussian);

    }

    else if (rr <= pdiffuse+pglossy+preflection)

    {

        //sample perfect specular reflection

        wi = reflect(hi.shading_normal, wo);

        pwi = 1.f;

        float cost = dot(hi.shading_normal, wo);

        fs = hi.reflection / (pwi * preflection * cost);

        sample_emitted = true;

    }

    else if (rr <= pdiffuse+pglossy+preflection+prefraction)

    {

        //sample perfect specular refraction

        bool not_tir = refract(hi.shading_normal, wo, 1.f/hi.ior, wi);

        assert(not_tir);

        pwi = 1.f;

        float cost = std::abs(dot(hi.shading_normal, wi));

        fs = hi.refraction / (pwi * prefraction * cost);

        sample_emitted = true;

    }

    else

        assert(false);

    //create aux ray

    ray s;

    s.origin = hi.position + epsilon * wi;

    s.direction = wi;

    s.depth = r.depth + 1;

    s.distance = std::numeric_limits<float>::infinity();

    float cost = std::abs(dot(hi.shading_normal, wi));

    Vec3f Li = cost * fs * trace(s, sample_emitted);

    //returm sum of emitted + direct + indirect

    return Le + Ld + Li;

}

Vec3f path_tracer::compute_pixel(int w, int h)

{

    assert(scene_);

    //supersample

    Vec3f L(0.f);

    for (int j=0; j<subsamples_; ++j)

    {

        float y  = h + (j + 0.5f) / subsamples_;

        for (int i=0; i<subsamples_; ++i)

        {

            float x  = w + (i + 0.5f) / subsamples_;

            //ask camera for initial ray..

            Vec2f uv(x/width_, y/height_);

            ray r = scene_->get_camera()->generate(uv);

            //trace ray

            L += trace(r, true);

        }

    }

    return L / float(subsamples_ * subsamples_);

}

//02566 framework, Anders Wang Kristensen, awk@imm.dtu.dk, 2007

#if 0

//02566 framework, Anders Wang Kristensen, awk@imm.dtu.dk, 2007

#include <stdlib.h>

#include <GL/glut.h>

#include <CGLA/Vec2i.h>

#include <CGLA/Vec3uc.h>

#include "scene.h"

#include "camera.h"

#include "mesh.h"

#include "omni.h"

#include "matte.h"

#include "plastic.h"

#include "metal.h"

#include "glass.h"

#include "path_tracer.h"

using namespace CGLA;

//global pointer to the active scene

scene* current;

static path_tracer* renderer;

const int width = 64*8;

const int height = 64*8;

static Vec3f* film;

static Vec3uc* image;

static Vec2i pixel(0);

static bool done = false;

static float dgamma = 2.2f;

static float dexposure = 0.f;

Vec3uc tonemap(const Vec3f& v)

{

    Vec3f u = v * std::pow(2.f, dexposure);

    float r = mt_random() - 0.5f;

    Vec3uc I;

    for (int i=0; i<3; ++i)

    {

        float c = std::pow(u[i], 1.f / dgamma);

        c = 255.f * c + 0.5f + r;

        I[i] = clamp(int(c), 0, 255);

    }

    return I;

}

void display(void)

{

    glClear(GL_COLOR_BUFFER_BIT);

    for (int j=0; j<height; ++j)

        for (int i=0; i<width; ++i)

            image[i + j*width] = tonemap(film[i + j*width]);

    glDrawPixels(width, height, GL_RGB, GL_UNSIGNED_BYTE, image);

    glutSwapBuffers();

    GLenum e = glGetError();

    if (e != GL_NO_ERROR)

    {

        printf("OpenGL error: %s\n", gluErrorString(e));

        exit(EXIT_FAILURE);

    }

}

void reshape(GLint width, GLint height)

{

    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();

    gluOrtho2D(0, width, 0, height);

    glMatrixMode(GL_MODELVIEW);

    glLoadIdentity();

}

void special(int key, int x, int y)

{

    switch (key)

    {

    case GLUT_KEY_LEFT:

        dgamma = std::max(dgamma - 0.1f, 0.5f);

        break;

    case GLUT_KEY_RIGHT:

        dgamma = std::min(dgamma + 0.1f, 5.f);

        break;

    case GLUT_KEY_DOWN:

        dexposure = std::max(dexposure - 0.1f, -10.f);

        break;

    case GLUT_KEY_UP:

        dexposure = std::min(dexposure + 0.1f, 10.f);

        break;

    }

    printf("gamma: %.2f, exposure: %.2f\n", dgamma, dexposure);

    glutPostRedisplay();

}

void keyboard(unsigned char key, int x, int y)

{

    switch (key)

    {

    case 27: //ESCAPE key

        exit(0);

        break;

    }

}

void idle(void)

{

    for (int i=0; i<width*8 && !done; ++i)

    {

        Vec3f L = renderer->compute_pixel(pixel[0], pixel[1]);

        film[pixel[0] + pixel[1] * width] = L;

        //advance

        ++pixel[0];

        if (pixel[0] == width)

        {

            pixel[0] = 0;

            ++pixel[1];

            if (pixel[1] == height)

            {

                done = true;

                glutIdleFunc(NULL);

            }

        }

    }

    glutPostRedisplay();

}

int main(int argc, char* argv[])

{

    //make the scene

    current = new scene;

    //setup some materials

    matte dull_white(Vec3f(0.5f, 0.5f, 0.5f));

    matte dull_gray(Vec3f(0.4f, 0.4f, 0.4f));

    matte dull_red(Vec3f(0.6f, 0.3f, 0.2f));

    matte dull_green(Vec3f(0.3f, 0.6f, 0.2f));

    matte dull_blue(Vec3f(0.2f, 0.2f, 0.6f));

    plastic glossy_white(Vec3f(0.4f, 0.4f, 0.4f), Vec3f(0.5f), 20.f);

    plastic glossy_purple(Vec3f(0.3f, 0.1f, 0.3f), Vec3f(0.65f), 8.f);

    plastic glossy_yellow(Vec3f(0.3f, 0.3f, 0.0f), Vec3f(0.65f), 32.f);

    //for exercise 2

    glass clear(Vec3f(0.99f, 0.99f, 0.99f), 1.5f);

    metal silver(Vec3f(0.9f, 0.9f, 0.9f), 22.f, 0.177f, 3.638f);

    //setup cornell box 1mx1mx1m

    mesh floor("../../data/cornell_box/floor.obj");

    floor.set_material(&glossy_white);

    current->insert(&floor);

    mesh ceiling("../../data/cornell_box/ceiling.obj");

    ceiling.set_material(&dull_gray);

    current->insert(&ceiling);

    mesh back("../../data/cornell_box/back.obj");

    back.set_material(&silver);

    current->insert(&back);

    mesh left("../../data/cornell_box/left.obj");

    left.set_material(&dull_red);

    current->insert(&left);

    mesh right("../../data/cornell_box/right.obj");

    right.set_material(&dull_blue);

    current->insert(&right);

    //add some objects to the box

    Mat4x4f tmp;

    mesh box1("../../data/cornell_box/box1.obj");

    tmp = rotation_Mat4x4f(YAXIS, -float(M_PI)/8.f);

    tmp = translation_Mat4x4f(Vec3f(-0.3f,0.f,-0.05f)) * tmp;

    box1.set_transform(tmp);

    box1.set_material(&dull_green);

    current->insert(&box1);

    mesh box2("../../data/cornell_box/box2.obj");

    tmp = translation_Mat4x4f(Vec3f(0.25f,0.f, -0.05f));

    box2.set_transform(tmp);

    box2.set_material(&glossy_purple);

    current->insert(&box2);

    mesh teapot("../../data/cornell_box/teapot1.obj");

    tmp = rotation_Mat4x4f(YAXIS, float(M_PI/4.f));

    tmp = translation_Mat4x4f(Vec3f(-0.25f,0.25f, -0.05)) * tmp;

    teapot.set_transform(tmp);

    teapot.set_material(&silver);

    current->insert(&teapot);

    mesh sphere1("../../data/cornell_box/sphere2.obj");

    tmp = translation_Mat4x4f(Vec3f(0.25f,0.45f,-0.05f));

    sphere1.set_transform(tmp);

    sphere1.set_material(&clear);

    current->insert(&sphere1);

    mesh sphere2("../../data/cornell_box/sphere2.obj");

    tmp = translation_Mat4x4f(Vec3f(0.22f,0.15f,0.25f));

    sphere2.set_transform(tmp);

    sphere2.set_material(&glossy_yellow);

    //current->insert(&sphere2);

    //light sources

    mesh quad_light("../../data/cornell_box/quad.obj");

    tmp = rotation_Mat4x4f(XAXIS, float(M_PI));

    tmp = translation_Mat4x4f(Vec3f(0.f,0.99f,0.2f)) * tmp;

    quad_light.set_transform(tmp);

    quad_light.set_exitance(Vec3f(300,300,300));

    current->insert(&quad_light);

    mesh quad_light1("../../data/cornell_box/quad.obj");

    tmp = rotation_Mat4x4f(XAXIS, float(M_PI));

    tmp = translation_Mat4x4f(Vec3f(0.f,0.99f,0.2f)) * tmp;

    quad_light1.set_transform(tmp);

    quad_light1.set_exitance(Vec3f(0,400,0));

//  current->insert(&quad_light1);

    mesh quad_light2("../../data/cornell_box/quad.obj");

    tmp = rotation_Mat4x4f(XAXIS, float(M_PI));

    tmp = translation_Mat4x4f(Vec3f(-0.2f,0.99f,0.2f)) * tmp;

    quad_light2.set_transform(tmp);

    quad_light2.set_exitance(Vec3f(400,0,0));

//  current->insert(&quad_light2);

    mesh quad_light3("../../data/cornell_box/quad.obj");

    tmp = rotation_Mat4x4f(XAXIS, float(M_PI));

    tmp = translation_Mat4x4f(Vec3f(0.2f,0.99f,0.2f)) * tmp;

    quad_light3.set_transform(tmp);

    quad_light3.set_exitance(Vec3f(0,0,400));

//  current->insert(&quad_light3);

    omni omni_light(Vec3f(30.f));

    omni_light.set_transform(translation_Mat4x4f(Vec3f(0.0f,0.95f,0.0f)));

    //current->insert(&omni_light);

    mesh sphere_light("../../data/cornell_box/small_sphere.obj");

    sphere_light.set_transform(translation_Mat4x4f(Vec3f(0.f,0.95f,0.f)));

    sphere_light.set_exitance(Vec3f(30.f/(4.f*float(M_PI)*0.01f*0.01f)));

    //current->insert(&sphere_light);

    //setup camera (eye, center, up, focal length)

    camera pentax(

        Vec3f(0.f,0.5f,2.0f),

        Vec3f(0.f,0.5f,0.5f),

        Vec3f(0,1,0),

        0.035f);

    current->set_camera(&pentax);

    //build acceleration structure

    current->initialize(8, 25);

    //create the renderer

    renderer = new path_tracer(width, height, true, 1);

    renderer->set_scene(current);

    //create the film

    film = new Vec3f[width * height];

    std::fill(film, film+width*height, Vec3f(0.3f));

    image = new Vec3uc[width * height];

    std::fill(image, image+width*height, Vec3uc(32,32,32));

    //init glut

    glutInit(&argc, argv);

    glutInitWindowSize(width, height);

    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);

    glutCreateWindow("Course 02566 - IMM DTU");

    glutDisplayFunc(display);

    glutReshapeFunc(reshape);

    glutKeyboardFunc(keyboard);

    glutSpecialFunc(special);

    glutIdleFunc(idle);

    //Turn the flow of control over to GLUT

    glutMainLoop();

    //clean up

    delete current;

    delete renderer;

    return EXIT_SUCCESS;

}

#endif