[Solved] Need help with rotation.
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 zoboomafoo
 Prole
 Posts: 7
 Joined: Sun May 19, 2013 9:05 pm
[Solved] Need help with rotation.
This is my 1st time posting on a forum so i don't really know if this is in the right section or what ever but...
I just started using love2d this morning and been doing good using the documentation until a couple of minutes ago.
I'm trying to make a 2d space combat game and i'm trying to make the ship rotate slowly to the mouse in the shortest distance. I have no idea how to do this and all my attempts just end up spinning wildly in one direction or dose fine until it goes from 180deg to 180deg where it goes back all the way around the other direction... please help
I just started using love2d this morning and been doing good using the documentation until a couple of minutes ago.
I'm trying to make a 2d space combat game and i'm trying to make the ship rotate slowly to the mouse in the shortest distance. I have no idea how to do this and all my attempts just end up spinning wildly in one direction or dose fine until it goes from 180deg to 180deg where it goes back all the way around the other direction... please help
Last edited by zoboomafoo on Wed May 22, 2013 9:48 pm, edited 4 times in total.
 zoboomafoo
 Prole
 Posts: 7
 Joined: Sun May 19, 2013 9:05 pm
Re: Rotate slowly to mouse.
No one can help me?
Re: Rotate slowly to mouse.
So if the mouse is moved on for example the x axis the ship will rotate?
 zoboomafoo
 Prole
 Posts: 7
 Joined: Sun May 19, 2013 9:05 pm
Re: Rotate slowly to mouse.
Any axis. I want the ship to slowly turn towards the mouse so you cant just instantly turn around backward and blap something behind you. so lets say the angle the ship is is 1.8 rads and the desired angle is 2 rads how do i get the ship to rotate at a set, constant speed toward the desired angle in the shortest direction?veethree wrote:So if the mouse is moved on for example the x axis the ship will rotate?
Re: Need help with rotation.
zoboomaffoo,
what you*re trying to do is quite possible. For doing thse things I'd strongly reccomend a vector library. HUMP has one and I'm using my own with operator overloading support which simplifies vector operations a lot. Using a vector library really makes your life much easier when doing these operations.
Ok let's try to solve your problems:If I understood you right you want to rotate the ship towards the mouse x and y position.
I'm doing this in a pseudo code kind of way as I don't know your code!
Step 1: Getting a distance vector from the ship to the mouse > ships position  mouse position
Distance.x, Distance.y = ship.x  mouse.x, ship.x  mouse.y
Step2: Geting the angular direction of our distance vector
Direction = math.atan2(Distance.y, Distance.x)
Step3: Comparing the shortest distance between the two angles.
angleDistance = math.min(Direction  ship.rotation, ship.rotation  Direction)
I'm storing the target rotation in the ships table:
ship.target = ship.rotation + angleDistance
Step 4: Rotation the ship towards the target in one second
Do this in love.udate()
if ship.rotation ~= ship.target then
ship.rotation = ship.rotation + angleDistance*dt
end
This is totally untested but you might get the idea. Feel free to ask if you don't understand a part or if it doesn't work as expected
what you*re trying to do is quite possible. For doing thse things I'd strongly reccomend a vector library. HUMP has one and I'm using my own with operator overloading support which simplifies vector operations a lot. Using a vector library really makes your life much easier when doing these operations.
Ok let's try to solve your problems:If I understood you right you want to rotate the ship towards the mouse x and y position.
I'm doing this in a pseudo code kind of way as I don't know your code!
Step 1: Getting a distance vector from the ship to the mouse > ships position  mouse position
Distance.x, Distance.y = ship.x  mouse.x, ship.x  mouse.y
Step2: Geting the angular direction of our distance vector
Direction = math.atan2(Distance.y, Distance.x)
Step3: Comparing the shortest distance between the two angles.
angleDistance = math.min(Direction  ship.rotation, ship.rotation  Direction)
I'm storing the target rotation in the ships table:
ship.target = ship.rotation + angleDistance
Step 4: Rotation the ship towards the target in one second
Do this in love.udate()
if ship.rotation ~= ship.target then
ship.rotation = ship.rotation + angleDistance*dt
end
This is totally untested but you might get the idea. Feel free to ask if you don't understand a part or if it doesn't work as expected
 zoboomafoo
 Prole
 Posts: 7
 Joined: Sun May 19, 2013 9:05 pm
Re: Need help with rotation.
The ship is just spinning around counter clockwise i will just post the .love file.mode7 wrote: Feel free to ask if you don't understand a part or if it doesn't work as expected
I got the HUMP library but dont get what it dose.For doing thse things I'd strongly reccomend a vector library. HUMP has one and I'm using my own with operator overloading support which simplifies vector operations a lot. Using a vector library really makes your life much easier when doing these operations.
 Attachments

 space.love
 Umm why dose it say conf.dat dosent exist when it is in the .love file?
 (11.26 KiB) Downloaded 82 times
Re: Need help with rotation.
Okay I kinda fixed it, the bigger problem seems to be to get the shortest distance to rotate the ship towards especially if it crosses a rotation of 0. Maybe I'm just stupid right now.
Code: Select all
function ship_Update(dt)
ship.speed = math.ceil(math.sqrt((math.pow(ship.xVel*10,2))+(math.pow(ship.yVel*10,2)))*10)
mouse = {}
mouse.x = love.mouse.getX()
mouse.y = love.mouse.getY()
rotspeed = 1
newAngle = math.atan2((mouse.y  ship.y), (mouse.x  ship.x))
newAngle = newAngle % (2*math.pi)
angleDistance = 0
if math.abs(newAngle  ship.angle) < math.abs(ship.angle  newAngle) then
angleDistance = newAngle  ship.angle
else
angleDistance = newAngle  ship.angle
end
ship.target = ship.angle + angleDistance
if ship.angle ~= ship.target then
ship.angle = ship.angle + angleDistance * (dt*rotspeed)
end
ship.angle = newAngle
ship.exel = ship.thrust/ship.mass*0.1
ship.xVel = ship.xVel + ship.exel * math.cos(ship.angle) * dt
ship.yVel = ship.yVel + ship.exel * math.sin(ship.angle) * dt
ship.x = ship.x + ship.xVel
ship.y = ship.y + ship.yVel
ship.yVel = ship.yVel * (1  math.min(dt * 1, 1))
ship.xVel = ship.xVel * (1  math.min(dt * 1, 1))
if love.keyboard.isDown("w") then
if ship.thrust < ship.maxThrust then
ship.thrust = ship.thrust + (ship.maxThrust/5) * dt
else
thrust = maxThrust
end
end
if love.keyboard.isDown("s") then
if ship.thrust > 0 then
ship.thrust = ship.thrust  (ship.maxThrust/10) * dt
else
ship.thrust = 0
end
end
if love.keyboard.isDown("x") then
ship.thrust=0
end
end
Re: Need help with rotation.
This is an error I suppose? The then and else branch both do the same thing.mode7 wrote:Code: Select all
if math.abs(newAngle  ship.angle) < math.abs(ship.angle  newAngle) then angleDistance = newAngle  ship.angle else angleDistance = newAngle  ship.angle end
Besides that: Starting from the ship.angle and the newAngle you can calculate the relative/differenceangle by this:
Code: Select all
angleDistance = (newAngleship.angle+math.pi)%(2*math.pi)math.pi
The sign of angleDistance tells you, if you need to turn clockwise or counterclockwise. (Or do it like you already do and multiply angleDistance by a rotational speed and dt)
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 zoboomafoo
 Prole
 Posts: 7
 Joined: Sun May 19, 2013 9:05 pm
Re: [Solved] Need help with rotation.
Thank you micha that equation is exactly what i was looking for.
Tanks to everyone else, mode7
Tanks to everyone else, mode7
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