/*

 * C++ RayTracer

 * file: raytracer.cc

 *

 * Radek Brich, 2006

 */

#ifdef PTHREADS

#include <pthread.h>

#endif

#include <stdio.h>

#include <malloc.h>

#include <float.h>

#include "raytracer.h"

// Hammersley spherical point distribution

// http://www.cse.cuhk.edu.hk/~ttwong/papers/udpoint/udpoints.html

Vector3 Raytracer::SphereDistribute(int i, int n, float extent, Vector3 &normal)

{

	float p, t, st, phi, phirad;

	int kk;

	t = 0;

	for (p=0.5, kk=i; kk; p*=0.5, kk>>=1)

	if (kk & 1)

		t += p;

	t = 1.0 + (t - 1.0)*extent;

	phi = (i + 0.5) / n;

	phirad =  phi * 2.0 * M_PI;

	st = sqrt(1.0 - t*t);

	float x, y, z, xx, yy, zz, q;

	x = st * cos(phirad);

	y = st * sin(phirad);

	z = t;

	// rotate against Y axis

	q = acos(normal.z);

	zz = z*cos(q) - x*sin(q);

	xx = z*sin(q) + x*cos(q);

	yy = y;

	// rotate against Z axis

	q = atan2f(normal.y, normal.x);

	x = xx*cos(q) - yy*sin(q);

	y = xx*sin(q) + yy*cos(q);

	z = zz;

	return Vector3(x, y, z);

}

// ---- tyto dve funkce budou v budouci verzi metody objektu PhongShader

// calculate shader function

// P is point of intersection, N normal in this point

Colour PhongShader_ambient(Material &mat, Vector3 &P)

{

	Colour col = mat.texture.colour; //mat.texture.evaluate(P);

	// ambient

	return mat.ambient * col;

}

/*

 P is point of intersection,

 N normal in this point,

 R direction of reflected ray,

 V direction to the viewer

*/

Colour PhongShader_calculate(Material &mat, Vector3 &P, Vector3 &N, Vector3 &R, Vector3 &V,

	Light &light)

{

	Colour I = Colour();

	Vector3 L = light.pos - P;

	L.normalize();

	float L_dot_N = dot(L, N);

	float R_dot_V = dot(R, V);

	Colour col = mat.texture.colour; //mat.texture.evaluate(P);

	// diffuse

	I = mat.diffuse * col * light.colour * L_dot_N;

	// specular

	if (R_dot_V > 0)

		I += mat.specular * light.colour * powf(R_dot_V, mat.shininess);

	return I;

}

Colour Raytracer::raytrace(Ray &ray, int depth, Shape *origin_shape)

{

	float nearest_distance = FLT_MAX; //Infinity

	Shape *nearest_shape = top->nearest_intersection(origin_shape, ray, nearest_distance);

	if (nearest_shape == NULL) {

		return bg_colour;

	} else {

		Colour acc = Colour();

		Vector3 P = ray.a + ray.dir * nearest_distance; // point of intersection

		Vector3 normal = nearest_shape->normal(P);

		acc = PhongShader_ambient(*nearest_shape->material, P);

		vector<Light*>::iterator light;

		for (light = lights.begin(); light != lights.end(); light++) {

			Vector3 jo, L = (*light)->pos - P; // direction vector to light

			L.normalize();

			float L_dot_N = dot(L, normal);

			if (L_dot_N > 0) {

				// test if this light is occluded (sharp shadows)

				if ((*light)->shadows) {

					Ray shadow_ray = Ray(P, L);

					float dist = FLT_MAX;

					if (top->nearest_intersection(nearest_shape, shadow_ray, dist))

						continue;

				}

				// shading function

				Vector3 R = L - 2.0 * L_dot_N * normal;

				acc += PhongShader_calculate(*nearest_shape->material,

					P, normal, R, ray.dir, **light);

			}

		}

		// reflection

		int trace_max_depth = 4;

		Vector3 newdir = ray.dir - 2.0 * dot(ray.dir, normal) * normal;

		if (depth < trace_max_depth && nearest_shape->material->reflection > 0.01) {

			Ray newray = Ray(P, newdir);

			Colour refl_col = raytrace(newray, depth + 1, nearest_shape);

			acc += nearest_shape->material->reflection * refl_col;

		}

		// refraction

		/* ... */

		// ambient occlusion

		if (ao_samples)

		{

			float miss = 0;

			for (int i = 0; i < ao_samples; i++) {

				Vector3 dir = SphereDistribute(i, ao_samples, ao_angle, normal);

				Ray ao_ray = Ray(P, dir);

				float dist = ao_distance;

				Shape *shape_in_way = top->nearest_intersection(nearest_shape, ao_ray, dist);

				if (shape_in_way == NULL)

					miss += 1.0;

				else

					miss += dist / ao_distance;

			}

			float ao_intensity = miss / ao_samples;

			acc = acc * ao_intensity;

		}

		return acc;

	}

}

static void *renderrow(void *data)

{

	RenderrowData *d = (RenderrowData*) data;

	for (int x = 0; x < d->w; x++) {

		// generate a ray from eye passing through this pixel

#if 1

		// no oversampling

		Vector3 dir = Vector3(d->vx, d->vy, 0) - d->eye;

		dir.normalize();

		Ray ray(d->eye, dir);

		Colour c = d->rt->raytrace(ray, 0, NULL);

#else

		// 5x oversampling

		Vector3 dir = Vector3();

		Colour c = Colour();

		for (int i = 0; i < 5; i++)

		{

			float osax[] = {0.0, -0.4, +0.4, +0.4, -0.4};

			float osay[] = {0.0, -0.4, -0.4, +0.4, +0.4};

			dir = Vector3(d->vx + osax[i] * d->dx,

				d->vy + osay[i]*d->dy , 0) - d->eye;

			dir.normalize();

			Ray ray(d->eye, dir);

			c += d->rt->raytrace(ray, 0, NULL);

		}

		c = c * (1./5);

#endif

		*(d->iter++) = c.r;

		*d->iter++ = c.g;

		*d->iter++ = c.b;

		d->vx += d->dx;

	}

#ifdef PTHREADS

	pthread_exit((void *)d);

#endif

	return (void *)d;

}

float *Raytracer::render(int w, int h)

{

	float *data;

	data = (float *) malloc(w*h*3*sizeof(float));

	if (!data)

		return NULL;

	float startx = -1.0 * 4, starty = (float)h/w * 4;

	float dx = -2*startx/w, dy = -2*starty/h;

	float vy;

	RenderrowData *d;

	printf("* building kd-tree\n");

	//cout << endl;

	//static_cast<KdTree*>(top)->save(cout);

	//cout << endl;

	//srand(time(NULL));

	// eye - viewing point

	Vector3 eye(0, 0, -5);

	// for each pixel...

	vy = starty;

#ifdef PTHREADS

	int num_threads = 4;

	printf("* pthreads enabled, using %d threads\n", num_threads);

	pthread_t threads[num_threads];

	for (int t = 0; t < num_threads; t++)

		threads[t] = pthread_self();

	int t = 0;

#endif

	printf("* rendering row   0 (  0%% done)");

	for (int y = 0; y < h; y++) {

		d = (RenderrowData*) malloc(sizeof(RenderrowData));

		d->rt = this;

		d->w = w;

		d->vx = startx;

		d->vy = vy;

		d->dx = dx;

		d->dy = dy;

		d->eye = eye;

		d->iter = data + y*3*w;

#ifdef PTHREADS

		/* create new thread and increase 't' */

		int rc = pthread_create(&threads[t++], NULL, renderrow, (void *)d);

		if (rc) {

			printf("\nERROR: return code from pthread_create() is %d\n", rc);

			exit(1);

		}

		/* when 't' owerflows, reset it */

		if (t >= num_threads)

			t = 0;

		/* wait for next thread in fifo queue, so the descriptor can be reused;

		   this also limits number of running threads */

		if (!pthread_equal(threads[t], pthread_self()))

			if (pthread_join(threads[t], (void**)&d) == 0)

				free(d);

#else

		renderrow((void *)d);

		free(d);

#endif

		vy += dy;

		printf("\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b%4d (%2d%% done)", y, y*100/(h-1));

	}

	printf("\n");

#ifdef PTHREADS

	printf("* waiting for threads to finish\n");

	for (t = 0; t < num_threads; t++)

		if (pthread_join(threads[t], (void**)&d) == 0)

			free(d);

#endif

	return data;

}

void Raytracer::addlight(Light *light)

{

	lights.push_back(light);

}

void Raytracer::ambientocclusion(int samples, float distance, float angle)

{

	ao_samples = samples;

	ao_distance = distance;

	ao_angle = angle;

	if (ao_distance == 0)

		/* 0 ==> Inf */

		ao_distance = FLT_MAX;

}