/*

 * C++ RayTracer

 * file: raytracer.cc

 *

 * Radek Brich, 2006

 */

#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;

	}

}

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

{

	int x, y;

	float *data, *iter;

	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 vx, vy;

	//srand(time(NULL));

	// eye - viewing point

	Vector3 eye(0, 0, -5);

	// for each pixel...

	iter = data;

	for (vy = starty, y = 0; y < h; y++) {

		vx = startx;

		for (x = 0; x < w; x++) {

			// generate a ray from eye passing through this pixel

#if 1

			// no oversampling

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

			dir.normalize();

			Ray ray(eye, dir);

			Colour c = 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(vx + osax[i]*dx,

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

				dir.normalize();

				Ray ray(eye, dir);

				c += raytrace(ray, 0, NULL);

			}

			c = c * (1./5);

#endif

			*iter++ = c.r;

			*iter++ = c.g;

			*iter++ = c.b;

			vx += dx;

		}

		vy += dy;

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

	}

	printf("\n");

	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;

}