#include "sphere.h"

#include <iostream>
using namespace std;

RayIntersect Sphere::CalcRayIntersect(Ray ray, int flags, int special)
{
	RayIntersect ri;
	ri.E = 0;
	ri.param_t = -1.0;

	vector3d o_c = ray.o - c;
	double B_2 = ray.d * o_c;

	if(B_2 > 0 && (flags & INTERSECT_ONLY))
		return ri;

	double C = o_c * o_c - r * r;
	double D = B_2 * B_2 - C;

	if(D <= 0.0) return ri;	// Does not intersect

	// if we only need to know the intersection, we can save time
	if(flags & INTERSECT_ONLY)
	{
		if(B_2*B_2 < D + 1e-10)
			return ri;

		ri.E = this;
		return ri;
	}

	D = sqrt(D);

	double t = -B_2 - D;

	if(t <= 1e-8) // Behind ray
	{
		t = B_2 - D;
		if(t <= 1e-8) return ri; // This one is behind the ray too.
	}

	ri.E = this;
	ri.param_t = t;
	return ri;
}

vector3d Sphere::CalcNormal(Ray ray, RayIntersect&ri)
{
	return (ray.o + ray.d * ri.param_t - c).ret_unit();
}

int Sphere::IntersectionTest(Ray ray, int flags, int special)
{
//	assert("depreciated" && 0);
	vector3d o_c = ray.o - c;
	double B_2 = ray.d * o_c;

	if(B_2 > 0) return 0;

	double C = o_c * o_c - r * r;
	double D = B_2 * B_2 - C;

	// no intersection
	if(D <= 0) return 0;

	// intersects behind me
	if(B_2*B_2 < D + 1e-10) return 0;

	return 1;
}

Color Sphere::GetTextureColor(Ray ray, RayIntersect& ri)
{
	static double pi = atan(1.0) * 4;
	if(!texture) return Color();
	vector3d v = (ray.o + ray.d * ri.param_t - c);
	v /= v.mag();
//	cout << v << endl;
	double x = v * unitx;
	double y = v * unity;
	double z = v * unitz;

	double theta = atan2(y, x);
//	if(y < 0) theta += pi;
	if(theta < 0) theta += 2 * pi;

	double phi = acos(-z);
	long col = texture->GetColor(theta/(2*pi), phi/pi);
	return Color(col);
}