/*

 * C++ RayTracer

 * file: scene.cc

 *

 * Radek Brich, 2006

 */

#include <math.h>

#include "scene.h"

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

{

	Vector3 V = ((Ray)ray).a - 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).a - 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;

}

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

{

	float dir = dot(N, ray.dir);

	if (dir != 0)

	{

		float newdist = -(dot(N, ray.a) + d) / dir;

		if (newdist > 0 && newdist < dist) {

			dist = newdist;

			return true;

		}

	}

	return false;

}

// 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.a;

	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;

}