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/* Copyright (C) 2004 MySQL AB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/**
* @file myx_gc_bsp.h
* @brief Implementation of a special BSP (binary space partitioning) tree.
*
*/
#ifndef __GC_BSP_H__
#define __GC_BSP_H__
#include "myx_gc_base.h"
class CGraphicElement;
class CHitResults;
//----------------------------------------------------------------------------------------------------------------------
/**
* A BSP (binary space partitioning) tree is a useful tool to greatly improve hit tests in complex scenes. This BSP class
* implements a special BSP tree that takes advantage of certain given aspects like always axis-aligned bounding boxes
* and 2D-only layout. This allows us to use an axis aligned partition, which always separates space into two equal halfs.
* Additionally, since we only need the BSP tree for hit tests it is not necessary to split the bounding boxes.
*/
class CBspTree
{
private:
// The element the tree consists of.
typedef struct tagBspEntry
{
bool isVertical; // Indicates whether the splitting straight line is vertical or horizontal. With this flag
// we can speed up classification as we only have to compare one value per vertex instead
// solving a line equation.
TBoundingBox bounds; // The bounds that this entry covers.
float splitPoint; // The actual partition value.
tagBspEntry* left; // Pointer to the left subtree.
tagBspEntry* right; // Pointer to the right subtree.
CGraphicElementList elements; // The list of elements convered by this BSP entry.
tagBspEntry()
{
isVertical = true;
left = NULL;
right = NULL;
};
} TBspEntry;
// Result for the bounding box classification.
typedef enum tagClassifiction
{
IS_UNKNOWN,
IS_LEFT,
IS_RIGHT,
IS_BOTH
} TClassification;
TBspEntry FRoot;
float FMinSize;
protected:
TClassification classify(TBspEntry* entry, CGraphicElement* element);
void deleteEntry(TBspEntry* entry);
CGraphicElement* findElement(TBspEntry* entry, TVertex point);
void findElements(TBspEntry* entry, TVertex point, CHitResults* hits);
void insertElement(TBspEntry*, CGraphicElement* element);
void renderEntry(TBspEntry* entry);
public:
CBspTree(float width, float height);
virtual ~CBspTree(void);
void addElement(CGraphicElement* element);
void clear(void);
CGraphicElement* findElement(TVertex point);
void findElements(TVertex point, CHitResults* hits);
void render(void);
};
//----------------------------------------------------------------------------------------------------------------------
#endif // __GC_BSP_H__
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