Lines and Tables?

[pr0sh4wn123]

Hello~ I am a beginner to love2d and lua in general. I am trying to make it so the user will be able to click with the left mouse button to create and drag a line to make their own custom line. I have this working fine (sort of) but I was wondering how would I make it so the user could do this with multiple lines. Like maybe finalizing the position by pressing space bar and creating a new line from where you left off to create a polygon! or maybe there is an easier way? Any help would be greatly appreciated and because I am new I was wondering if I could add anyone to Skype or somewhere so I can bounce ideas off them and ask for help? Okie thanks! here is my code so far:

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function love.load()
	mouse = {}
	love.graphics.setBackgroundColor(255, 255, 255)
	mouse.x, mouse.y = 0
	x, y = 600, 375
	x2, y2 = 600, 375
end

function love.draw()
	love.graphics.setColor(0, 0, 0)
	love.graphics.line(x, y, x2, y2)
end

function love.update(dt)
	mouse.x, mouse.y = love.mouse.getPosition()
	if love.mouse.isDown('l') then
		x = mouse.x
		y = mouse.y
	end
	if love.mouse.isDown('r') then
		x2 = mouse.x
		y2 = mouse.y
	end
end

[Zilarrezko]

This is a pretty simple fix, although there are several routes you can take.

My skype is zilarrezko_natvyr and I can answer some simple questions to the intermediate. However I'm pretty busy right now so I'll try and make this quick!

I made this actually earlier, but this is just a concept and kinda sucks, I would suggest finding a way to not use var and not use x2's and y2's and the like. but here's my code, pretty crappy. But one of the smarter guys will swing by and probably help you sooo much better.

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function love.load()
	line = {
	}
        var1 = false
end

function love.draw()
	if var1 then
		love.graphics.setColor(255,255,255,255)
		love.graphics.setLineWidth(10)
		love.graphics.line(varx, vary, mousex, mousey)
	end
	for k, v in ipairs(line) do
		love.graphics.setColor(255,255,255,255)
		love.graphics.setLineWidth(10)
		love.graphics.line(v.x, v.y, v.x2, v.y2)
	end
end

function love.update(dt)
	mousex, mousey = love.mouse.getPosition()
end

function love.mousepressed(x, y, b)
	if b == "l" then
		var1 = true
		varx, vary = x, y
	end
end

function love.mousereleased(x, y, b)
	if b == "l" then
		var1 = false
		table.insert(line, {
			x = varx,
			y = vary,
			x2 = x,
			y2 = y
		})
	end
end

I'll be available in about two days, because the next couple of days I'm graduating and quite busy. Have fun with LÖVE!

[Roland_Yonaba]

Hi,

One thing interesting with love.graphics.line is it can takes either a vararg (variable number of arguments) and deduces couple of coordinates from it for drawing, or a table of coordinates positions, in array form.

So basically, if you want the user to draw a line linking all vertices, point by point, i would suggest implementing it as-is: create an empty table, and make it so that anytime the user clicks, it appends to this table the coordinates where the mouse was clicked.
Then in your draw loop, you will just have to pass that very table to love.graphics.line.

Code: Select all

function love.load()
  vertices = {}
end

function love.draw()
  love.graphics.line(vertices ) -- draws the line linking all vertices
 
  -- draws a line from the last vertex to the actual mouse position
  local mx, my = love.mouse.getPosition()
  love.graphics.line(vertices [#vertices -2],vertices [#vertices -1], mx, my)
end

-- callback called anytime the user presses a mouse button
function love.mousepressed(x, y, button)
  if button == 'l' then  -- if left-mouse click
    table.insert(vertices , x) 
    table.insert(vertices , y)
  end
end

Hope this helps.

[HugoBDesigner]

I think what you want is this:

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function love.load()
	current = {}
	lines = {}
	pressing = false
	love.graphics.setLineWidth(3)
end

function love.update(dt)
	if pressing then
		current[3] = love.mouse.getX()
		current[4] = love.mouse.getY()
	end
end

function love.draw()
	love.graphics.setColor(255, 255, 255, 255)
	for i, v in pairs(lines) do
		love.graphics.line(unpack(v))
	end
	love.graphics.setColor(205, 205, 255, 255)
	if pressing then
		love.graphics.line(unpack(current))
	end
end

function love.mousepressed(x, y, b)
	if b == "l" then
		pressing = true
		current[1] = x
		current[2] = y
	end
end

function love.mousereleased(x, y, b)
	if b == "l" then
		pressing = false
		table.insert(lines, table.copy(current))
		current = {}
	end
end

function table.copy(t)
	local r = {}
	for i, v in pairs(t) do
		r[i] = v
	end
	return r
end

This method allows multiple lines...

[pr0sh4wn123]

Thank you for all the replies, but sadly I am getting nowhere, because I can not understand some parts of the code, for example this stuff:

Code: Select all

for k, v in ipairs(line) do
      love.graphics.setColor(255,255,255,255)
      love.graphics.setLineWidth(10)
      love.graphics.line(v.x, v.y, v.x2, v.y2)
   end

or this stuff:
(mainly the #s ??? I don't have a clue what you are doing there)

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love.graphics.line(vertices [#vertices -2],vertices [#vertices -1], mx, my)

and even this:

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function table.copy(t)
   local r = {}
   for i, v in pairs(t) do
      r[i] = v
   end
   return r
end

This is completely over my head, and I am sure I need a tutorial, but like I said I am a beginner. I am not sure how this works 100% yet.

[davisdude]

What do you not understand?
As for the "#s" that gets the length, or the number of items in a table/array (not counting nil values).

[pr0sh4wn123]

OH Ok I see, the number signs make sense, but now the only part I am confused on is doing the "for" function. Are there any proper/good tutorials for them? Or do you think you could explain them? Sorry for all the hassle >.<

[Karai17]

There are two types of for loops in Lua: One is a foreach loop, the other is a normal for loop.

In a normal for loop, you pick a starting point and an end point and the loop will add or subtract 1 each time until the limit is reached:

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for index=1, 100 do
    print(index) -- 1, 2, 3...98, 99, 100
end

In the foreach loop, we iterate through a table and pull out all the data within it, one row at a time. ipairs is used for indexed tables (there the keys are integers starting from 1), pairs can be used for both indexed or associated tables (the keys can be of any format)

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for key, value in ipairs(indexed_table) do
    print(key, value) -- 1, some data; 2, more data; 3, even more
end

for key, value in pairs(associated_table) do
    print(key, value) -- x, 123; name, Billy; y, 456; 11, wurds
end

[Roland_Yonaba]

This is completely over my head, and I am sure I need a tutorial, but like I said I am a beginner. I am not sure how this works 100% yet.

So maybe you should concentrate your efforts first to get comfortable with Lua's syntax ?
You can use this quick tutorial, this "cheat-sheet" (direct pdf link), BlackBullet's Lua for Programmers series, and best PiL (you do not even need to read everything in it).
It will help getting comfortable with the language first. And it won't be that long, since Lua is a little language and the syntax is easy to grasp.

[pr0sh4wn123]

Well I rather like learning while doing a project, so by doing this line project I was hoping to learn more lua, but thanks everyone for all the help, with all this I am sure I can complete what I wanted to do~!