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-- License CC0 (Creative Commons license) (c) darkfrei, 2023
-- infinity area cutting
love.window.setTitle ('crop infinity area by the line')
area = {lines={}}
tempLine = {}
local function pseudoScalarProduct(x1, y1, x2, y2, x3, y3, x4, y4)
local dx1, dy1 = x2-x1, y2-y1
local dx2, dy2 = x4-x3, y4-y3
-- positive - goes inside, clockwise
return dx1 * dy2 - dx2 * dy1
end
local function findIntersection(x1, y1, x2, y2, x3, y3, x4, y4, unlimStart1, unlimEnd1, unlimStart2, unlimEnd2)
local dx1, dy1 = x2-x1, y2-y1
local dx2, dy2 = x4-x3, y4-y3
local denominator = dx1*dy2-dy1*dx2
if denominator == 0 then
return nil -- Линии параллельны или совпадают
end
local dx13, dy13 = (x1 - x3), (y1 - y3)
local t = (dx13 * (y3 - y4) - dy13 * (x3 - x4)) / denominator
local u = (dx13 * (y1 - y2) - dy13 * (x1 - x2)) / denominator
if (unlimStart1 or t >= 0) and
(unlimEnd1 or t <= 1) and
(unlimStart2 or u >= 0) and
(unlimEnd2 or u <= 1) then
local intersectionX = x1 + t * (x2 - x1)
local intersectionY = y1 + t * (y2 - y1)
return intersectionX, intersectionY
end
-- return nil
end
local function checkCollisions(area, segment)
local startUnlimited = true
local endUnlimited = true
local segmentValid = false
local x1, y1, x2, y2 = segment[1], segment[2], segment[3], segment[4]
for i, aLine in ipairs (area.lines) do
local x3, y3 = aLine.startPoint[1], aLine.startPoint[2]
local x4, y4 = aLine.endPoint[1], aLine.endPoint[2]
-- negative for clockwise direction:
local psp = pseudoScalarProduct(x1, y1, x2, y2, x3, y3, x4, y4)
local us1, ue1 = startUnlimited, endUnlimited
local us2, ue2 = aLine.startUnlimited, aLine.endUnlimited
if psp < 0 then
local cx, cy = findIntersection(x1, y1, x2, y2, x3, y3, x4, y4, us1, ue1, us2, ue2)
if cx then
startUnlimited = false
segment[1], segment[2] = cx, cy
aLine.endPoint[1] = cx
aLine.endPoint[2] = cy
aLine.endUnlimited = false
segmentValid = true
else
-- no intersection
end
elseif psp > 0 then
local cx, cy = findIntersection(x1, y1, x2, y2, x3, y3, x4, y4, us1, ue1, us2, ue2)
if cx then
endUnlimited = false
segment[3], segment[4] = cx, cy
aLine.startPoint[1] = cx
aLine.startPoint[2] = cy
aLine.startUnlimited = false
segmentValid = true
else
-- no intersection
end
else
-- parallel
-- no intersection
end
end
-- here some cleaning for old not used area lines
return startUnlimited, endUnlimited
end
local function cutArea (area, segment)
-- local startUnlimited = true
local startUnlimited = true
local endUnlimited = true
-- local endUnlimited = false
if #segment < 4 then return end
startUnlimited, endUnlimited = checkCollisions(area, segment)
local x1, y1, x2, y2 = segment[1], segment[2], segment[3], segment[4]
local dx, dy = x2 - x1, y2 - y1
local w, h = love.graphics.getDimensions()
if (startUnlimited or endUnlimited) and dy ~= 0 then
local xMin, yMin, xMax, yMax = 10, 10, w - 10, h - 10
local slope = dx / dy
-- Calculate extended points for the starting point
local xStart, yStart
local xEnd, yEnd
if dy > 0 then
--min max
xStart = x1 + (yMin - y1) * slope
yStart = yMin
xEnd = x1 + (yMax - y1) * slope
yEnd = yMax
else
-- max min
xStart = x1 + (yMax - y1) * slope
yStart = yMax
xEnd = x1 + (yMin - y1) * slope
yEnd = yMin
end
-- if xStart < xMin or xStart > xMax or xEnd < xMin or xEnd > xMax then
if xStart < xMin or xStart > xMax then
if dx > 0 then
-- min max
yStart = y1 + (xMin - x1) / slope
xStart = xMin
else
yStart = y1 + (xMax - x1) / slope
xStart = xMax
end
end
if xEnd < xMin or xEnd > xMax then
if dx > 0 then
yEnd = y1 + (xMax - x1) / slope
xEnd = xMax
else
yEnd = y1 + (xMin - x1) / slope
xEnd = xMin
end
end
if startUnlimited then
x1, y1 = xStart, yStart
end
if endUnlimited then
x2, y2 = xEnd, yEnd
end
elseif (startUnlimited or endUnlimited) and dy == 0 then
-- Handling the case when the line segment is horizontal (dy == 0)
local xMin, xMax = 10, w - 10
-- Calculate extended points for the starting point
local xStart = dx > 0 and xMin or xMax
local yStart = y1
-- Calculate extended points for the ending point
local xEnd = dx > 0 and xMax or xMin
local yEnd = y2
if startUnlimited then
x1, y1 = xStart, yStart
end
if endUnlimited then
x2, y2 = xEnd, yEnd
end
end
local line = {
startPoint = {x1, y1},
endPoint = {x2, y2},
startUnlimited = startUnlimited,
endUnlimited = endUnlimited,
}
table.insert(area.lines, line)
end
function love.load()
end
function love.update(dt)
end
local function drawCutLine (line)
if #line > 3 then
love.graphics.line (line)
end
end
local function drawInfinityArea(area)
for _, line in ipairs(area.lines) do
local startPoint = line.startPoint
local endPoint = line.endPoint
love.graphics.line(startPoint[1], startPoint[2], endPoint[1], endPoint[2])
end
end
function love.draw()
love.graphics.setLineWidth (3)
love.graphics.setColor (0.6,0.6,0.6)
drawInfinityArea (area)
love.graphics.setColor (1,1,1)
drawCutLine (tempLine)
end
function love.mousepressed(x, y)
tempLine = {x, y}
end
function love.mousemoved (x, y)
tempLine[3] = x
tempLine[4] = y
-- tempLine[4] = tempLine[2]
end
function love.mousereleased ( x, y)
cutArea (area, tempLine)
tempLine = {}
end
function love.keypressed(key, scancode, isrepeat)
if false then
elseif key == "escape" then
love.event.quit()
end
end- 2023-07-22T19_29_05-NVIDIA GeForce Overlay DT.png (10.27 KiB) Viewed 36360 times
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