[Solved] How to make an object move in 8 directions

[nice]

Hello!

So a week or so I came back to Löve2D and I started to play around with it and at the moment I've implemented a very simple movement code that moves a rectangle in 4 different directions:

Code: Select all

function love.load()
	--Movement
	-- movePlayer = true
	moveX = 100
	moveY = 100

	cyan = love.graphics.setColor(0, 255, 255)
	pink = love.graphics.setColor(255, 105, 180)
end

function love.update(dt)
	-- Super simple movement
	if love.keyboard.isDown("w") then
		moveY = moveY - 100 * dt
	elseif love.keyboard.isDown("a") then
		moveX = moveX - 100 * dt 
	elseif love.keyboard.isDown("s") then
		moveY = moveY + 100 * dt
	elseif love.keyboard.isDown("d") then
		moveX = moveX + 100 * dt
	end

end

function love.draw()
	-- A square
	love.graphics.rectangle("line",moveX, moveY, 50, 50)

	love.graphics.setColor{math.random(0,255),math.random(0, 255), math.random(0,255)}
	-- love.graphics.setBackgroundColor{math.random(0,255),math.random(0, 255), math.random(0,255)}
	-- love.graphics.setBackgroundColor{0, math.random(250, 255), math.random(0,255)}
	-- love.graphics.setBackgroundColor{math.random(120, 255), 0, math.random(120,255)}
	
end

What I would like to do now is implement a way to move my player object in 8 different directions and I'm wondering how it's done.
Do I need to use velocity? friction? or some combination?

[drunken_munki]

Code: Select all

function love.update(dt)
	-- Super simple movement
	if love.keyboard.isDown("w") then
		moveY = moveY - 100 * dt
	elseif love.keyboard.isDown("s") then
		moveY = moveY + 100 * dt
	end
	
	if love.keyboard.isDown("a") then
		moveX = moveX - 100 * dt 
	elseif love.keyboard.isDown("d") then
		moveX = moveX + 100 * dt
	end

end

Try this for your love.update, if I understood your question properly.

[Sir_Silver]

So you're saying that currently you can only move up OR down OR left OR right, and you want your guy to, for instance, move up AND left or up AND right etc...

The reason you're not able to do that with your current code is because you are using the elseif statement. Just seperate each check into it's own if statement (similar to what drunken_munki did) and viola, you now have octa-directional movement.

[nice]

Code: Select all

function love.update(dt)
	-- Super simple movement
	if love.keyboard.isDown("w") then
		moveY = moveY - 100 * dt
	elseif love.keyboard.isDown("s") then
		moveY = moveY + 100 * dt
	end
	
	if love.keyboard.isDown("a") then
		moveX = moveX - 100 * dt 
	elseif love.keyboard.isDown("d") then
		moveX = moveX + 100 * dt
	end

end

Try this for your love.update, if I understood your question properly.

So you're saying that currently you can only move up OR down OR left OR right, and you want your guy to, for instance, move up AND left or up AND right etc...

The reason you're not able to do that with your current code is because you are using the elseif statement. Just seperate each check into it's own if statement (similar to what drunken_munki did) and viola, you now have octa-directional movement.

Well that was easier than I've expected.. thanks!

[zorg]

That solution still has one thing that may or may not be an issue for you, and it has to do with geometry;
moving one unit diagonally doesn't equal moving one unit on two axes separately; you're doing the latter here, which may work for a tile-based game, but if you want consistent movement speed in all directions, you'd want to do it a bit differently:

Code: Select all

local sqrt2 = math.sqrt(2)
function love.update(dt)
	-- Super simple movement
	local dx, dy = 0.0, 0.0
	if love.keyboard.isDown("w") then
		dy = -100
	elseif love.keyboard.isDown("s") then
		dy = 100
	end
	
	if love.keyboard.isDown("a") then
		dx = -100
	elseif love.keyboard.isDown("d") then
		dx = 100
	end
	
	if dx ~= 0.0 and dy ~= 0.0 then
	    -- Diagonal movement (as in 45°)
	    dx, dy = dx / sqrt2, dy / sqrt2
	end
	
	moveX = moveX + dx * dt
	moveY = moveY + dy * dt

end

[MrFariator]

If you don't care about the mathematical formulas (or absolute accuracy), and your diagonals are at 45 degree angles, you can also apply the magic constant 0.707 to multiply vertical and horizontal speed to get diagonal speed.

[zorg]

If you don't care about the mathematical formulas (or absolute accuracy), and your diagonals are at 45 degree angles, you can also apply the magic constant 0.707 to multiply vertical and horizontal speed to get diagonal speed.

math.cos(math.rad(45)) == 0.70710678118655
https://forum.yoyogames.com/index.php?t ... ctor.1039/

[MrFariator]

The magic constant can be found mentioned in books and quite a few other places, yes, if that's what you're trying to hint at with the link. In fact, after first calculating it myself when learning game programming in Flash some ten years ago, I also found out it was a built-in property in Flash Lite 2.0 (Math.SQRT1_2, ie. math.sqrt(1/2)), and I've been using the number occasionally since.

Anyway, for a sizable chunk of games with fixed octagonal movement (like maybe a simple Zelda clone) you can just use the first few significant digits because they don't usually deal with large velocities or numbers, thus just using 0.707 is "good enough". More so if you don't even care about sub-pixel coordinates.

Of course, your approach is more handy for a more general case, and can be used for other angles too.