/*

 * Pyrit Ray Tracer

 * file: octree.cc

 *

 * Radek Brich, 2006-2007

 */

#include "octree.h"

OctreeNode::~OctreeNode()

{

	if (shapes != NULL)

		delete shapes;

	else

		delete[] children;

}

void OctreeNode::subdivide(BBox bbox, int maxdepth)

{

	if (maxdepth <= 0 || shapes->size() <= 4)

		return;

	// make children

	children = new OctreeNode[8];

	// evaluate centres for axes

	const Float xsplit = (bbox.L.x + bbox.H.x)*0.5;

	const Float ysplit = (bbox.L.y + bbox.H.y)*0.5;

	const Float zsplit = (bbox.L.z + bbox.H.z)*0.5;

	// set bounding boxes for children

	BBox childbb[8] = {bbox, bbox, bbox, bbox, bbox, bbox, bbox, bbox};

	for (int i = 0; i < 4; i++)

	{

		// this is little obfuscated, so on right are listed affected children

		// the idea is to cut every axis once per child, making 8 combinations

		childbb[i].H.x = xsplit;	// 0,1,2,3

		childbb[i+4].L.x = xsplit;  // 4,5,6,7

		childbb[i+(i>>1<<1)].H.y = ysplit;	// 0,1,4,5

		childbb[i+(i>>1<<1)+2].L.y = ysplit;// 2,3,6,7

		childbb[i<<1].H.z = zsplit;		// 0,2,4,6

		childbb[(i<<1)+1].L.z = zsplit; // 1,3,5,7

	}

	// distribute shapes to children

	ShapeList::iterator sh;

	unsigned int shapenum = 0;

	for (sh = shapes->begin(); sh != shapes->end(); sh++)

	{

			{

			}

	}

	if (shapes->size() <= 8 && shapenum > 2*shapes->size())

	{

		// bad subdivision, revert

		delete[] children;

		return;

	}

	// remove shapes and set this node to non-leaf

	delete shapes;

	shapes = NULL;

	// recursive subdivision

	for (int i = 0; i < 8; i++)

		children[i].subdivide(childbb[i], maxdepth-1);

}

void Octree::build()

{

	dbgmsg(1, "* building octree\n");

	root = new OctreeNode();

	ShapeList::iterator shape;

	for (shape = shapes.begin(); shape != shapes.end(); shape++)

		root->addShape(*shape);

	root->subdivide(bbox, max_depth);

	built = true;

}

static inline int first_node(const Float tx0, const Float ty0, const Float tz0,

	const Float txm, const Float tym, const Float tzm)

{

	int res = 0;

	if (tx0 > ty0)

	{

		if (tx0 > tz0)

		{ // YZ

			if (tym < tx0)

				res |= 2;

			if (tzm < tx0)

				res |= 1;

		}

		else

		{ // XY

			if (txm < tz0)

				res |= 4;

			if (tym < tz0)

				res |= 2;

		}

	}

	else

	{

		if (ty0 > tz0)

		{ // XZ

			if (txm < ty0)

				res |= 4;

			if (tzm < ty0)

				res |= 1;

			return res;

		}

		else

		{ // XY

			if (txm < tz0)

				res |= 4;

			if (tym < tz0)

				res |= 2;

		}

	}

	return res;

}

static inline int next_node(const Float txm, const int xnode,

	const Float tym, const int ynode, const Float tzm, const int znode)

{

	if (txm < tym)

	{

		if (txm < tzm)

			return xnode;

		else

			return znode;

	}

	else

	{

		if (tym < tzm)

			return ynode;

		else

			return znode;

	}

}

static Shape *proc_subtree(const int a, const Float tx0, const Float ty0, const Float tz0,

	const Float tx1, const Float ty1, const Float tz1, OctreeNode *node,

	const Shape *origin_shape, const Ray &ray, Float &nearest_distance)

{

	Float txm, tym, tzm;

	int curr_node;

	// if ray does not intersect this node

	if (tx1 < 0.0 || ty1 < 0.0 || tz1 < 0.0)

		return NULL;

	if (node->isLeaf())

	{

		Shape *nearest_shape = NULL;

		ShapeList::iterator shape;

		Float mindist = max(max(tx0,ty0),tz0);

		Float dist = min(min(min(tx1,ty1),tz1),nearest_distance);

		for (shape = node->shapes->begin(); shape != node->shapes->end(); shape++)

			if (*shape != origin_shape && (*shape)->intersect(ray, dist) && dist >= mindist)

			{

				nearest_shape = *shape;

				nearest_distance = dist;

			}

		return nearest_shape;

	}

	txm = 0.5 * (tx0+tx1);

	tym = 0.5 * (ty0+ty1);

	tzm = 0.5 * (tz0+tz1);

	curr_node = first_node(tx0,ty0,tz0,txm,tym,tzm);

	Shape *shape = NULL;

	while (curr_node < 8)

	{

		switch (curr_node)

		{

			case 0:

				shape =proc_subtree (a,tx0,ty0,tz0,txm,tym,tzm,node->getChild(a), origin_shape, ray, nearest_distance);

				curr_node = next_node(txm, 4, tym, 2, tzm, 1);

				break;

			case 1:

				shape =proc_subtree (a,tx0,ty0,tzm,txm,tym,tz1,node->getChild(1^a), origin_shape, ray, nearest_distance);

				curr_node = next_node(txm, 5, tym, 3, tz1, 8);

				break;

			case 2:

				shape =proc_subtree (a,tx0,tym,tz0,txm,ty1,tzm,node->getChild(2^a), origin_shape, ray, nearest_distance);

				curr_node = next_node(txm, 6, ty1, 8, tzm, 3);

				break;

			case 3:

				shape =proc_subtree (a,tx0,tym,tzm,txm,ty1,tz1,node->getChild(3^a), origin_shape, ray, nearest_distance);

				curr_node = next_node(txm, 7, ty1, 8, tz1, 8);

				break;

			case 4:

				shape =proc_subtree (a,txm,ty0,tz0,tx1,tym,tzm,node->getChild(4^a), origin_shape, ray, nearest_distance);

				curr_node = next_node(tx1, 8, tym, 6, tzm, 5);

				break;

			case 5:

				shape =proc_subtree (a,txm,ty0,tzm,tx1,tym,tz1,node->getChild(5^a), origin_shape, ray, nearest_distance);

				curr_node = next_node(tx1, 8, tym, 7, tz1, 8);

				break;

			case 6:

				shape =proc_subtree (a,txm,tym,tz0,tx1,ty1,tzm,node->getChild(6^a), origin_shape, ray, nearest_distance);

				curr_node = next_node(tx1, 8, ty1, 8, tzm, 7);

				break;

			case 7:

				shape =proc_subtree (a,txm,tym,tzm,tx1,ty1,tz1,node->getChild(7^a), origin_shape, ray, nearest_distance);

				curr_node = 8;

				break;

		}

		if (shape != NULL)

			return shape;

	}

	return NULL;

}

/*

traversal algorithm paper as described in paper

"An Efficient Parametric Algorithm for Octree Traversal"

by J. Revelles, C. Urena and M. Lastra.

*/

Shape * Octree::nearest_intersection(const Shape *origin_shape, const Ray &ray,

		Float &nearest_distance)

{

	/* if we have no tree, fall back to naive test */

	if (!built)

		return Container::nearest_intersection(origin_shape, ray, nearest_distance);

	int a = 0;

	Vector3 ro = ray.o;

	Vector3 rdir = ray.dir;

	if (rdir.x < 0.0)

	{

		ro.x = (bbox.L.x+bbox.H.x) - ro.x;

		rdir.x = -rdir.x;

		a |= 4;

	}

	if (rdir.y < 0.0)

	{

		ro.y = (bbox.L.y+bbox.H.y) - ro.y;

		rdir.y = -rdir.y;

		a |= 2;

	}

	if (rdir.z < 0.0)

	{

		ro.z = (bbox.L.z+bbox.H.z) - ro.z;

		rdir.z = -rdir.z;

		a |= 1;

	}

	Float tx0 = (bbox.L.x - ro.x) / rdir.x;

	Float tx1 = (bbox.H.x - ro.x) / rdir.x;

	Float ty0 = (bbox.L.y - ro.y) / rdir.y;

	Float ty1 = (bbox.H.y - ro.y) / rdir.y;

	Float tz0 = (bbox.L.z - ro.z) / rdir.z;

	Float tz1 = (bbox.H.z - ro.z) / rdir.z;

	if (max(max(tx0,ty0),tz0) < min (min(tx1,ty1),tz1))

		return proc_subtree(a,tx0,ty0,tz0,tx1,ty1,tz1,root,

			origin_shape, ray, nearest_distance);

	else

		return NULL;

}