/*
 * 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);
}

inline Shape *Raytracer::nearest_intersection(const Shape *origin_shape, const Ray &ray,
	float &nearest_distance)
{
	Shape *nearest_shape = NULL;
	ShapeList::iterator shape;
	for (shape = shapes.begin(); shape != shapes.end(); shape++)
		if (*shape != origin_shape && (*shape)->intersect(ray, nearest_distance))
			nearest_shape = *shape;
	return nearest_shape;
}

// ---- 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 = 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 (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 = 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
}

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;

	//srand(time(NULL));

	// eye - viewing point
	Vector3 eye(0, 0, -5);

	// for each pixel...
	vy = starty;

#ifdef PTHREADS
	int num_threads = 20;
	printf("* pthreads enabled, using %d threads\n", num_threads);
	pthread_t threads[num_threads];
	for (int t = 0; t < num_threads; t++)
		threads[t] = NULL;
	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 (threads[t] != NULL)
			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::addshape(Shape *shape)
{
	shapes.push_back(shape);
}

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;
}