/*

 * C++ RayTracer

 * file: scene.cc

 *

 * Radek Brich, 2006

 */

#include <math.h>

#include "common.h"

#include "scene.h"

/* http://www.siggraph.org/education/materials/HyperGraph/raytrace/rtinter3.htm */

bool BBox::intersect(const Ray &ray, float &a, float &b)

{

	float tnear = -FLT_MAX;

	float tfar = FLT_MAX;

	float t1, t2;

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

	{

		if (ray.dir.cell[i] == 0) {

			/* ray is parallel to these planes */

			if (ray.o.cell[i] < L.cell[i] || ray.o.cell[i] > H.cell[i])

				return false;

		} else

		{

			/* compute the intersection distance of the planes */

			t1 = (L.cell[i] - ray.o.cell[i]) / ray.dir.cell[i];

			t2 = (H.cell[i] - ray.o.cell[i]) / ray.dir.cell[i];

			if (t1 > t2)

				swap(t1, t2);

			if (t1 > tnear)

				tnear = t1; /* want largest Tnear */

			if (t2 < tfar)

				tfar = t2; /* want smallest Tfar */

			if (tnear > tfar)

				return false; /* box missed */

			if (tfar < 0)

				return false; /* box is behind ray */

		}

	}

	a = tnear;

	b = tfar;

	return true;

}

bool Sphere::intersect(const Ray &ray, float &dist)

{

	Vector3 V = ((Ray)ray).o - center;

	float Vd = - dot(V, ray.dir);

	float Det = Vd * Vd - (dot(V,V) - sqr_radius);

	if (Det > 0) {

		Det = sqrtf(Det);

		float t1 = Vd - Det;

		if (t1 > 0)

		{

			if (t1 < dist) {

				dist = t1;

				return true;

			}

		} else {

			float t2 = Vd + Det;

			if (t2 > 0)

			{

				// ray from inside of the sphere

				dist = t2;

				return true;

			}

		}

	}

	return false;

}

bool Sphere::intersect_all(const Ray &ray, float dist, vector<float> &allts)

{

	//allts = new vector<float>();

	Vector3 V = ((Ray)ray).o - center;

	float Vd = - dot(V, ray.dir);

	float Det = Vd * Vd - (dot(V,V) - sqr_radius);

	if (Det > 0) {

		Det = sqrtf(Det);

		float t1 = Vd - Det;

		float t2 = Vd + Det;

		if (t1 < 0)

		{

			if (t2 > 0)

			{

				// ray from inside of the sphere

				allts.push_back(0.0);

				allts.push_back(t2);

				return true;

			}

			else

				return false;

		}

		else

		{

			allts.push_back(t1);

			allts.push_back(t2);

			return true;

		}

	}

	return false;

}

BBox Sphere::get_bbox()

{

	BBox bbox = BBox();

	bbox.L = center - radius;

	bbox.H = center + radius;

	return bbox;

}

bool Box::intersect(const Ray &ray, float &dist)

{

	float b;

	return get_bbox().intersect(ray, dist, b);

}

Vector3 Box::normal(Vector3 &P)

{

	Vector3 N;

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

	{

		if (P.cell[i] >= L.cell[i]-Eps && P.cell[i] <= L.cell[i]+Eps)

		//if (P.cell[i] == L.cell[i])

		{

			N.cell[i] = -1.0;

			break;

		}

		if (P.cell[i] >= H.cell[i]-Eps && P.cell[i] <= H.cell[i]+Eps)

		//if (P.cell[i] == H.cell[i])

		{

			N.cell[i] = +1.0;

			break;

		}

	}

	return N;

}

// this initialization and following intersection methods implements

// Fast Triangle Intersection algorithm from

// http://www.mpi-inf.mpg.de/~wald/PhD/

Triangle::Triangle(const Vector3 &aA, const Vector3 &aB, const Vector3 &aC, Material *amaterial)

	: A(aA), B(aB), C(aC)

{

	material = amaterial;

	Vector3 c = B - A;

	Vector3 b = C - A;

	N = cross(c, b);

	if (fabsf(N.x) > fabsf(N.y))

	{

		if (fabsf(N.x) > fabsf(N.z))

			k = 0;

		else

			k = 2;

	}

	else

	{

		if (fabsf(N.y) > fabsf(N.z))

			k = 1;

		else

			k = 2;

	}

	int u = (k + 1) % 3;

	int v = (k + 2) % 3;

	float krec = 1.0f / N[k];

	nu = N[u] * krec;

	nv = N[v] * krec;

	nd = dot(N, A) * krec;

	// first line equation

	float reci = 1.0f / (b[u] * c[v] - b[v] * c[u]);

	bnu = b[u] * reci;

	bnv = -b[v] * reci;

	// second line equation

	cnu = c[v] * reci;

	cnv = -c[u] * reci;

	// finalize normal

	N.normalize();

}

// see comment for previous method

bool Triangle::intersect(const Ray &ray, float &dist)

{

	Vector3 O = ray.o;

	Vector3 D = ray.dir;

	const int modulo3[5] = {0,1,2,0,1};

	const int ku = modulo3[k+1];

	const int kv = modulo3[k+2];

	const float lnd = 1.0f / (D[k] + nu * D[ku] + nv * D[kv]);

	const float t = (nd - O[k] - nu * O[ku] - nv * O[kv]) * lnd;

	if (!(t < dist && t > 0))

		return false;

	float hu = O[ku] + t * D[ku] - A[ku];

	float hv = O[kv] + t * D[kv] - A[kv];

	float beta = hv * bnu + hu * bnv;

	if (beta < 0)

		return false;

	float gamma = hu * cnu + hv * cnv;

	if (gamma < 0)

		return false;

	if ((beta + gamma) > 1)

		return false;

	dist = t;

	return true;

}

BBox Triangle::get_bbox()

{

	BBox bbox = BBox();

	bbox.L = A;

	if (B.x < bbox.L.x)  bbox.L.x = B.x;

	if (C.x < bbox.L.x)  bbox.L.x = C.x;

	if (B.y < bbox.L.y)  bbox.L.y = B.y;

	if (C.y < bbox.L.y)  bbox.L.y = C.y;

	if (B.z < bbox.L.z)  bbox.L.z = B.z;

	if (C.z < bbox.L.z)  bbox.L.z = C.z;

	bbox.H = A;

	if (B.x > bbox.H.x)  bbox.H.x = B.x;

	if (C.x > bbox.H.x)  bbox.H.x = C.x;

	if (B.y > bbox.H.y)  bbox.H.y = B.y;

	if (C.y > bbox.H.y)  bbox.H.y = C.y;

	if (B.z > bbox.H.z)  bbox.H.z = B.z;

	if (C.z > bbox.H.z)  bbox.H.z = C.z;

	return bbox;

};