LÖVE

Code: Select all

function update( dt )
  local p1 = line.point1
  local p2 = line.point2
  hit = true
  if p1.x < x and p2.x < x then
    hit = false
    return
  end
  
  if p1.x > x + w and p2.x > x + w then
    hit = false
    return
  end
  
  if p1.y < y and p2.y < y then
    hit = false
    return
  end
  
  if p1.y > y+h and p2.y > y+h then
    hit = false
    return
  end  
  
  -- last case: first build normal vector
  local nx,ny = p2.y-p1.y, -(p2.x-p1.x)
  local vx,vy = x-p1.x, y-p1.y
  
  local min = nx*vx+ny*vy
  local max = min
  
  vx,vy = x+w-p1.x, y-p1.y
  min = math.min(min,nx*vx+ny*vy)
  max = math.max(max,nx*vx+ny*vy)
  
  vx,vy = x+w-p1.x, y+h-p1.y
  min = math.min(min,nx*vx+ny*vy)
  max = math.max(max,nx*vx+ny*vy)
  
  vx,vy = x-p1.x, y+h-p1.y
  min = math.min(min,nx*vx+ny*vy)
  max = math.max(max,nx*vx+ny*vy)    
  
  if min*max>0 then
    hit = false
  end 
end

Code: Select all

local function getSegmentIntersectionIndices(l,t,w,h, x1,y1,x2,y2)
  local t1, t2 = 0, 1
  local dx, dy = x2-x1, y2-y1
  local p, q, r

  for side = 1,4 do
    if     side == 1 then p,q = -dx, x1 - l     -- left
    elseif side == 2 then p,q =  dx, l + w - x1 -- right
    elseif side == 3 then p,q = -dy, y1 - t     -- top
    else                  p,q =  dy, t + h - y1 -- bottom
    end

    if p == 0 then
      if q <= 0 then return nil end
    else
      r = q / p
      if p < 0 then
        if     r > t2 then return nil
        elseif r > t1 then t1 = r
        end
      else -- p > 0
        if     r < t1 then return nil
        elseif r < t2 then t2 = r
        end
      end
    end
  end

  local xi1, yi1 = x1 + dx*t1, y1 + dy*t1
  local xi2, yi2 = x1 + dx*t2, y1 + dx*t2

  return xi1, yi1, xi2, yi2
end