fov.cpp

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** Copyright (C) 2002-2007 Bjoern Bergstroem
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/*
 *
 * implementation of recursive shadowcasting
 *
 * 020125: Bjoern Bergstroem - changed from float to double to remove compiler
 *         warnings
 * 020125: Bjoern Bergstroem - included a check to avoid orthogonal edges to be
 *         scanned more than once
 * 020125: Greg McIntyre - declared the nwL, neL etc in FOV::start outside the
 *         for loops
 *
 */

#include "fov.h"
#include "oublietteplan.h"
#include <stdlib.h>

double FOV::slope(double x1, double y1, double x2, double y2)
{
	double xDiff=x1-x2;
	double yDiff=y1-y2;

	if(yDiff != 0)
	{
		return xDiff/yDiff;
	}
	else
	{
		return 0;
	}
}

double FOV::invSlope(double x1, double y1, double x2, double y2)
{
	double slope=this->slope(x1,y1,x2,y2);

	if(slope != 0)
	{
		return 1/slope;
	}
	else
	{
		return 0;
	}
}


/* scanNW2N
	scans the octant covering the area from north west to north from left to 
	right
	the method ignores the octants starting and ending cells since they have
	been applied in FOV::start
*/
void FOV::scanNW2N(OublietteLevel *map, int xCenter, int yCenter, int distance, int maxRadius, double startSlope, double endSlope)
{
	if(distance > maxRadius)
	{
		return;
	}

	// calculate start and end cell of the scan
	int xStart=(int)((double)xCenter + 0.5 - (startSlope * distance));
	int xEnd=(int)((double)xCenter + 0.5 - (endSlope * distance));
	int yCheck=yCenter - distance;

	// is the starting cell the leftmost cell in the octant?
	// NO: call applyCell() to starting cell 
	// YES: it has already been applied in FOV::start()
	if(xStart != xCenter-(1*distance))
	{
		this->applyCell(map,xStart,yCheck);
	}

	// find out if starting cell blocks LOS
	bool prevBlocked=this->scanCell(map,xStart,yCheck);

	// scan from the cell after the starting cell (xStart+1) to end cell of
	// scan (xCheck<=xEnd)
	for(int xCheck=xStart+1; xCheck<=xEnd; xCheck++)
	{
		// is the current cell the rightmost cell in the octant?
		// NO: call applyCell() to current cell 
		// YES: it has already been applied in FOV::start()
		if(xCheck != xCenter)
		{
			// apply cell
			this->applyCell(map,xCheck,yCheck);
		}
		
		// cell blocks LOS
		// if previous cell didn't block LOS (prevBlocked==false) we have
		// hit a 'new' section of walls. a new scan will be started with an
		// endSlope that 'brushes' by to the left of the blocking cell
		//
		// +---+a####+---+  @ = [xCenter+0.5,yCenter+0.5]
		// |   |#####|   |  a = old [xCheck,yCheck]
		// |   |#####|   |  b = new [xCheck-0.00001,yCheck+0.99999]
		// |   |#####|   |
		// +---b#####+---+
		// +---++---++---+
		// |   ||   ||   |
		// |   ||   || @ |
		// |   ||   ||   |
		// +---++---++---+
		//
		if(this->scanCell(map,xCheck,yCheck))
		{
			if(!prevBlocked)
			{
				this->scanNW2N(map,xCenter,yCenter,distance+1,maxRadius,startSlope,this->slope((double)xCenter+0.5,(double)yCenter+0.5,(double)xCheck-0.000001,(double)yCheck+0.999999));
			}
			prevBlocked=true;
		}

		// cell doesn't block LOS
		// if the cell is the first non-blocking cell after a section of walls
		// we need to calculate a new startSlope that 'brushes' by to the right
		// of the blocking cells
		//
		// #####a---++---+  @ = [xCenter+0.5,yCenter+0.5]
		// #####|   ||   |  a = new and old [xCheck,yCheck]
		// #####|   ||   |
		// #####|   ||   |
		// #####+---++---+
		// +---++---++---+
		// |   ||   ||   |
		// |   ||   || @ |
		// |   ||   ||   |
		// +---++---++---+
		//
		else
		{
			if(prevBlocked)
			{
				startSlope=this->slope((double)xCenter+0.5,(double)yCenter+0.5,(double)xCheck,(double)yCheck);
			}
			prevBlocked=false;
		}
	}

	// if the last cell of the scan didn't block LOS a new scan should be
	// started
	if(!prevBlocked)
	{
		this->scanNW2N(map,xCenter,yCenter,distance+1,maxRadius,startSlope,endSlope);
	}
}


/* scanNE2N
	scans the octant covering the area from north east to north from right to 
	left
	the method ignores the octants starting and ending cells since they have
	been applied in FOV::start
*/
void FOV::scanNE2N(OublietteLevel *map, int xCenter, int yCenter, int distance, int maxRadius, double startSlope, double endSlope)
{
	if(distance > maxRadius)
	{
		return;
	}

	// calculate start and end cell of the scan
	int xStart=(int)((double)xCenter + 0.5 - (startSlope * distance));
	int xEnd=(int)((double)xCenter + 0.5 - (endSlope * distance));
	int yCheck=yCenter - distance;

	// is starting cell the rightmost cell in the octant?
	// NO: call applyCell() to starting cell 
	// YES: it has already been applied in FOV::start()
	if(xStart != xCenter-(-1*distance))
	{
		this->applyCell(map,xStart,yCheck);
	}

	// find out if starting cell blocks LOS
	bool prevBlocked=this->scanCell(map,xStart,yCheck);

	// scan from the cell after the starting cell (xStart-1) to end cell of
	// scan (xCheck>=xEnd)
	for(int xCheck=xStart-1; xCheck>=xEnd; xCheck--)
	{
		// is the current cell the leftmost cell in the octant?
		// NO: call applyCell() to current cell 
		// YES: it has already been applied in FOV::start()
		if(xCheck != xCenter)
		{
			// apply cell
			this->applyCell(map,xCheck,yCheck);
		}
		
		// cell blocks LOS
		// if previous cell didn't block LOS (prevBlocked==false) we have
		// hit a 'new' section of walls. a new scan will be started with an
		// endSlope that 'brushes' by to the right of the blocking cell
		//
		// +---+a####+---+  @ = [xCenter+0.5,yCenter+0.5]
		// |   |#####|   |  a = old [xCheck,yCheck]
		// |   |#####|   |  b = new [xCheck+0.9999,yCheck-0.00001]
		// |   |#####|   |
		// +---+#####b---+
		// +---++---++---+
		// |   ||   ||   |
		// | @ ||   ||   |
		// |   ||   ||   |
		// +---++---++---+
		//
		if(this->scanCell(map,xCheck,yCheck))
		{
			if(!prevBlocked)
			{
				this->scanNE2N(map,xCenter,yCenter,distance+1,maxRadius,startSlope,this->slope((double)xCenter+0.5,(double)yCenter+0.5,(double)xCheck+1,(double)yCheck+0.99999));
			}
			prevBlocked=true;
		}

		// cell doesn't block LOS
		// if the cell is the first non-blocking cell after a section of walls
		// we need to calculate a new startSlope that 'brushes' by to the left
		// of the blocking cells
		//
		// +---+a---b#####  @ = [xCenter+0.5,yCenter+0.5]
		// |   ||   |#####  a = old [xCheck,yCheck]
		// |   ||   |#####  b = new [xCheck+0.99999,yCheck]
		// |   ||   |#####
		// +---++---+#####
		// +---++---++---+
		// |   ||   ||   |
		// | @ ||   ||   |
		// |   ||   ||   |
		// +---++---++---+
		//
		else
		{
			if(prevBlocked)
			{
				startSlope=this->slope((double)xCenter+0.5,(double)yCenter+0.5,(double)xCheck+0.9999999,(double)yCheck);
			}
			prevBlocked=false;
		}
	}

	// if the last cell of the scan didn't block LOS a new scan should be
	// started
	if(!prevBlocked)
	{
		this->scanNE2N(map,xCenter,yCenter,distance+1,maxRadius,startSlope,endSlope);
	}
}


/* scanNW2W
	scans the octant covering the area from north west to west from top to 
	bottom
	the method ignores the octants starting and ending cells since they have
	been applied in FOV::start
*/
void FOV::scanNW2W(OublietteLevel *map, int xCenter, int yCenter, int distance, int maxRadius, double startSlope, double endSlope)
{
	if(distance > maxRadius)
	{
		return;
	}

	// calculate start and end cell of the scan
	int yStart=(int)((double)yCenter + 0.5 - (startSlope * distance));
	int yEnd=(int)((double)yCenter + 0.5 - (endSlope * distance));
	int xCheck=xCenter - distance;

	// is starting cell the topmost cell in the octant?
	// NO: call applyCell() to starting cell 
	// YES: it has already been applied in FOV::start()
	if(yStart != yCenter-(1*distance))
	{
		this->applyCell(map,xCheck,yStart);
	}

	// find out if starting cell blocks LOS
	bool prevBlocked=this->scanCell(map,xCheck,yStart);

	// scan from the cell after the starting cell (yStart+1) to end cell of
	// scan (yCheck<=yEnd)
	for(int yCheck=yStart+1; yCheck<=yEnd; yCheck++)
	{
		// is the current cell the bottommost cell in the octant?
		// NO: call applyCell() to current cell 
		// YES: it has already been applied in FOV::start()
		if(yCheck != yCenter)
		{
			// apply cell
			this->applyCell(map,xCheck,yCheck);
		}
		
		// cell blocks LOS
		// if previous cell didn't block LOS (prevBlocked==false) we have
		// hit a 'new' section of walls. a new scan will be started with an
		// endSlope that 'brushes' by the top of the blocking cell (see fig.)
		//
		// +---++---++---+  @ = [xCenter+0.5,yCenter+0.5]
		// |   ||   ||   |  a = old [xCheck,yCheck]
		// |   ||   ||   |  b = new [xCheck+0.99999,yCheck-0.00001]
		// |   ||   ||   |
		// +---b+---++---+
		// a####+---++---+
		// #####|   ||   |
		// #####|   ||   |
		// #####|   ||   |
		// #####+---++---+
		// +---++---++---+
		// |   ||   ||   |
		// |   ||   || @ |
		// |   ||   ||   |
		// +---++---++---+
		//
		if(this->scanCell(map,xCheck,yCheck))
		{
			if(!prevBlocked)
			{
				this->scanNW2W(map,xCenter,yCenter,distance+1,maxRadius,startSlope,this->invSlope((double)xCenter+0.5,(double)yCenter+0.5,(double)xCheck+0.99999,(double)yCheck-0.00001));
			}
			prevBlocked=true;
		}

		// cell doesn't block LOS
		// if the cell is the first non-blocking cell after a section of walls
		// we need to calculate a new startSlope that 'brushes' by the bottom
		// of the blocking cells
		//
		// #####+---++---+  @ = [xCenter+0.5,yCenter+0.5]
		// #####|   ||   |  a = old and new [xCheck,yCheck]
		// #####|   ||   |
		// #####|   ||   |
		// #####+---++---+
		// a---++---++---+
		// |   ||   ||   |
		// |   ||   ||   |
		// |   ||   ||   |
		// +---++---++---+