Line of sight algorithm

I have been trying to find a algorithm which when given a integer which will determine "sight range" will produce a two dimensional array containing all the x,y values of tiles which fulfill x+y<=sight range in both positive and negative directions.

This is the method I used to accomplish this:

for (int y=0;y<mapHeight;y++)
{
for (int x=0;x<mapWidth;x++)
{
if(currentMap.getUnit(x, y)!=null)
{
int sightRange = currentMap.getUnit(x, y).getMovementRange()/2;
for(int sightStepY = -sightRange;sightStepY<sightRange;sightStepY++)
{
for(int sightStepX = -sightRange;sightStepX<sightRange;sightStepX++)
{
if(x+sightStepX>=0&&x+sightStepX<mapWidth&&y+sightStepY>=0&&y+sightStepY<mapHeight)
{

if(sightStepY>=0&&sightStepX>=0)
{
if(sightStepY+sightStepX<=sightRange)
{
currentMap.fogArray[x+sightStepX][y+sightStepY]=0;
}
}

if(y+sightRange<mapHeight){
currentMap.fogArray[x][y+sightRange]=0;}
if(x+sightRange<mapHeight){
currentMap.fogArray[x+sightRange][y]=0;}


if(sightStepY<=0&&sightStepX>=0)
{
if(sightStepX-sightStepY<=sightRange)
{
currentMap.fogArray[x+sightStepX][y+sightStepY]=0;
}
}

if(sightStepY<=0&&sightStepX<=0)
{
if(-sightStepX-sightStepY<=sightRange)
{
currentMap.fogArray[x+sightStepX][y+sightStepY]=0;
}
}

if(sightStepY>=0&&sightStepX<=0)
{
if(sightStepY-sightStepX<=sightRange)
{
currentMap.fogArray[x+sightStepX][y+sightStepY]=0;
}
}

}}}
}}}

Fog array is the two dimensional array which states if the tile should fog(1) or not (0).
Here is an example of the result when rendered in the game:

I think the above is rather messy and was achieved with a good deal of trial and error. I'm sure there is a more elegant way of achieving this. Any suggestions would be appreciated.