LOS Tiles

gistfile1.txt

--given a 2D table "tiles" with a cell for each tile on the ground, and each cell containing a list of objects
--in that cell,find all cells which are in line of sight between points A and T 
--s is cellsize (square)
--tiles is a 2D table
--results will be passed back in a table
--so if tile[3][4] is in line of sight, then (whatever is in) tiles[3][4] will be added to the results
function GetTiles(T,A,s,tiles)
    local x0,y0,x1,y1=T.x/s,T.z/s,A.x/s,A.z/s --tile positions of the two points
    local dx = abs(x1-x0)
    local dy = abs(y1-y0)
    local huge=99999
    local tt={}
    
    local x = floor(x0)
    local y = floor(y0)

    local n = 1
    local x_inc, y_inc, error

    if dx == 0 then
        x_inc = 0
        error = huge
    elseif x1 > x0 then
        x_inc = 1
        n = n + floor(x1) - x
        error = (floor(x0) + 1 - x0) * dy
    else
        x_inc = -1
        n = n + x - floor(x1)
        error = (x0 - floor(x0)) * dy
    end
    
    if dy == 0 then
        y_inc = 0
        error =error - huge
    elseif (y1 > y0) then
        y_inc = 1
        n = n + floor(y1) - y
        error = error - (floor(y0) + 1 - y0) * dx
    else
        y_inc = -1;
        n = n + y - floor(y1)
        error = error - (y0 - floor(y0)) * dx
    end

    for i = n,1,-1 do
        tt[#tt+1]=tiles[x][y]
        if error > 0 then 
            y = y + y_inc
            error = error - dx
        else
            x = x + x_inc
            error = error + dy
        end
    end
    return tt
end