I'm trying to create a circle of objects (boxes) for a mod from one game using this code:
function circle(x,y,r) local angle = 0 x = x + 0.5 - (x + 0.5) % 1 y = y + 0.5 - (x + 0.5) % 1 r = r + 0.5 прибавляю 0.5 чтобы объект появлялся в центре клетки while angle < 2*math.pi do angle = angle + r/r^2 local xs = (x + r * math.cos (angle)) local ys = (y + r * math.sin (angle)) game.surfaces[1].create_entity{name = "wooden-chest", position= {xs,ys},force='player'} --создание объекта с указанными координатами end end Objects can be placed only in the middle of the cell. that is, if the coordinates for example are x = 0.9 y = 0.9, then the object will be located on the coordinates x = 0.5 y = 0.5. Also with negative coordinates x = -0.9 y = -0.9 ==> x = -0.5 y = -0.5. Create a circle: circle (0,0,15)
Blue arrows indicate that the object has been re-located in these places (double shadow is visible). I have highlighted inconsistencies with the orange rectangle. With a radius of 10 and a half cells, the circle becomes even, but re-placement in the same cell is present:
What should be corrected in this function so that the circle correctly passes through the middle of the cells? Perhaps the Brezenham algorithm or the Midpoint circle algorithm would help me, but I don’t know how to write them in lua, as I’m still quite weak in programming. UPD: I tried to convert this code to C ++ in Lua:
public static void BresenhamCircle(Graphics g, Color clr, int _x, int _y, int radius) { int x = 0, y = radius, gap = 0, delta = (2 - 2 * radius); while (y >= 0) { PutPixel(g, clr, _x + x, _y + y, 255); PutPixel(g, clr, _x + x, _y - y, 255); PutPixel(g, clr, _x - x, _y - y, 255); PutPixel(g, clr, _x - x, _y + y, 255); gap = 2 * (delta + y) - 1; if (delta < 0 && gap <= 0) { x++; delta += 2 * x + 1; continue; } if (delta > 0 && gap > 0) { y--; delta -= 2 * y + 1; continue; } x++; delta += 2 * (x - y); y--; } } function bresenham_circle(X1,Y1,R) local x = 0 local y = R local gap = 0 local delta = (2 - 2 * R) while (y >= 0) do game.surfaces[1].create_entity{name = "wooden-chest", position= {X1 + x, Y1 + y},force='player'} game.surfaces[1].create_entity{name = "wooden-chest", position= {X1 + x, Y1 - y},force='player'} game.surfaces[1].create_entity{name = "wooden-chest", position= {X1 - x, Y1 + y},force='player'} game.surfaces[1].create_entity{name = "wooden-chest", position= {X1 - x, Y1 - y},force='player'} gap = 2 * (delta + y) - 1 if (delta >= 0 and gap > 0) then if (delta <= 0 and gap <= 0) then y = y - 1 x =x+1 delta = delta +2 *(xy) else y=y - 1 delta = delta-2*y+1 end else x=x+1 delta = delta+ 2 * x + 1 end end end But I get an Oval, one square away from the center on both axes, and also having a double-placement in 4 places UPD2: Offset was decided by adding 0.5 to x and y 
Now my code looks like this:
function bresenham_circle(X1,Y1,R) local R = R+0.5 local x = 0.25 local y = R local gap = 0 local delta = (2 - 2 * R) while (y >= 0) do game.surfaces[1].create_entity{name = "wooden-chest", position= {X1 + x, Y1 - y},force='player'} game.surfaces[1].create_entity{name = "wooden-chest", position= {X1 - x, Y1 - y},force='player'} game.surfaces[1].create_entity{name = "wooden-chest", position= {X1 - x, Y1 + y},force='player'} game.surfaces[1].create_entity{name = "wooden-chest", position= {X1 + x, Y1 + y},force='player'} gap = 2 * (delta + y) - 1 if (delta >= 0 and gap > 0) then if (delta <= 0 and gap <= 0) then y = y - 1 x =x+1 delta = delta +2 *((x)-(y)) else delta = delta-2*(y-1)+1 y=y - 1 end else delta = delta+ 2 * (x+1) + 1 x=x+1 end end end No repetitions with any radius, but still no symmetry. Any tips? 
xory(integer) for it differs from the previous one. - MBo