I’m having a problem when I rotate an object using transition.to( player, { rotation = rotationangle, time=400, transition=continuousLoop } )
I’m using the standard : local angleInDegrees = (math.deg(math.atan2( (y2-y1), (x2-x1))))
My player will rotate the long way round the circle instead of rotating using the shortest rotation path.
Is this a corona problem or am I missing something?
On object:rotate(delta), a positive number rotates the object clockwise and a negative number rotates the object counter-clockwise.
So if the same logic applies to transitions, I suppose if the rotation is greater than it was before the transition, it will rotate clockwise, and if it’s smaller, it will rotate counter-clockwise.
Here is a picture to describe the problem:
I want to rotate from one blue point to the other.
The green arrow is the rotation I want to follow.
The red is the rotation that actually happens.
Thanks, Greg
Yep, I understand the problem. The angle you’re specifying in “rotationangle” must be smaller than the angle the object had before the transition. Here’s some example code:
local r = display.newRect(200, 200, 100, 100) transition.to(r, {time = 3000, rotation = 500, onComplete=function() transition.to(r, {time = 3000, rotation = 200}) end})
This rotates the rectangle 500 degrees clockwise, then 300 degrees counter-clockwise.
This is my rotate function:
function getImageRotationPlayer(x1,y1,x2,y2)
if x1 ~=nil and y1 ~=nil and x2~=nil and y2~=nil then
local angleInDegrees = (math.deg(math.atan2( (y2-y1), (x2-x1))))
return angleInDegrees
else
return 0
end
end
I then rotate and move:(px and py are touch locations)
local rotationangle =getImageRotationPlayer(player.x, player.y, px,py)
transition.to( player, { rotation = rotationangle, time=400, transition=continuousLoop } )
mte.moveSpriteTo({sprite = player, levelPosX = px, levelPosY = py, time = 1500, transition = easing.inOutSine, onComplete = mte.setCameraFocus(player), })
** The thing is that the angle is correct,the quirkyness is that it moves the longer way to get there!
I tried to calculate distance and rotation direction but no go!
local endangle =getImageRotationPlayer(player.x, player.y, px,py)
local startangle = player.rotation
print ("PLAYER ANGLE : "… tostring(player.rotation))
print ("ROTATION ANGLE : "… tostring(endangle))
local direction = (startangle < endangle) and 1 or -1
local distance = math.abs(endangle - startangle)
print ("DISTANCE : "… tostring(distance))
local step_direction
if distance < 180 then
step_direction = direction
else
step_direction = -direction
end
trotation = distance * step_direction
transition.to( player, { rotation = trotation, time=400, transition=easing.linear } )
hi @gb8,
Have you look into @horacebury’s indispensable mathlib.lua?
https://gist.github.com/HoraceBury/9431861
I remember using his library years before for rotation of some kind.
You may try using angleOf and rotateTo functions.
Sorry i could not find the code i used before.
Good Luck!
burhan
burhan, you just saved me!!! Horace had it coverd using this function after calculating the angle:
function smallestAngleDiff( target, source )
local a = target - source
if (a > 180) then
a = a - 360
elseif (a < -180) then
a = a + 360
end
return a
end
Seems so simple now!!! Many thanks, Greg
On object:rotate(delta), a positive number rotates the object clockwise and a negative number rotates the object counter-clockwise.
So if the same logic applies to transitions, I suppose if the rotation is greater than it was before the transition, it will rotate clockwise, and if it’s smaller, it will rotate counter-clockwise.
Here is a picture to describe the problem:
I want to rotate from one blue point to the other.
The green arrow is the rotation I want to follow.
The red is the rotation that actually happens.
Thanks, Greg
Yep, I understand the problem. The angle you’re specifying in “rotationangle” must be smaller than the angle the object had before the transition. Here’s some example code:
local r = display.newRect(200, 200, 100, 100) transition.to(r, {time = 3000, rotation = 500, onComplete=function() transition.to(r, {time = 3000, rotation = 200}) end})
This rotates the rectangle 500 degrees clockwise, then 300 degrees counter-clockwise.
This is my rotate function:
function getImageRotationPlayer(x1,y1,x2,y2)
if x1 ~=nil and y1 ~=nil and x2~=nil and y2~=nil then
local angleInDegrees = (math.deg(math.atan2( (y2-y1), (x2-x1))))
return angleInDegrees
else
return 0
end
end
I then rotate and move:(px and py are touch locations)
local rotationangle =getImageRotationPlayer(player.x, player.y, px,py)
transition.to( player, { rotation = rotationangle, time=400, transition=continuousLoop } )
mte.moveSpriteTo({sprite = player, levelPosX = px, levelPosY = py, time = 1500, transition = easing.inOutSine, onComplete = mte.setCameraFocus(player), })
** The thing is that the angle is correct,the quirkyness is that it moves the longer way to get there!
I tried to calculate distance and rotation direction but no go!
local endangle =getImageRotationPlayer(player.x, player.y, px,py)
local startangle = player.rotation
print ("PLAYER ANGLE : "… tostring(player.rotation))
print ("ROTATION ANGLE : "… tostring(endangle))
local direction = (startangle < endangle) and 1 or -1
local distance = math.abs(endangle - startangle)
print ("DISTANCE : "… tostring(distance))
local step_direction
if distance < 180 then
step_direction = direction
else
step_direction = -direction
end
trotation = distance * step_direction
transition.to( player, { rotation = trotation, time=400, transition=easing.linear } )
hi @gb8,
Have you look into @horacebury’s indispensable mathlib.lua?
https://gist.github.com/HoraceBury/9431861
I remember using his library years before for rotation of some kind.
You may try using angleOf and rotateTo functions.
Sorry i could not find the code i used before.
Good Luck!
burhan
burhan, you just saved me!!! Horace had it coverd using this function after calculating the angle:
function smallestAngleDiff( target, source )
local a = target - source
if (a > 180) then
a = a - 360
elseif (a < -180) then
a = a + 360
end
return a
end
Seems so simple now!!! Many thanks, Greg
Hi gb8,
I got the same problem here and I understand all the logic behind this equation:
function smallestAngleDiff( target, source )
local a = target - source
if (a > 180) then
a = a - 360
elseif (a < -180) then
a = a + 360
end
return a
end
The thing I don’t understand is how to callback the last angle (source) I had the move before…
Hi gb8,
I have the same problem here and I understand all the logic behind this:
function smallestAngleDiff( target, source )
local a = target - source
if (a > 180) then
a = a - 360
elseif (a < -180) then
a = a + 360
end
return a
end
My problem is that i don’t know how to callback the last angle (source) I had the move before…
Hi leo,
– First get the angle between the two points
local rotationangle =getImageRotation(player.x, player.y, px,py)
– Figure out which way to turn
local angle = smallestAngleDiff( player.rotation, rotationangle)
– do the turn
transition.to( player, { rotation = player.rotation- angle, time=400, transition=easing.linear } )
function getImageRotation(x1,y1,x2,y2)
if x1 ~=nil and y1 ~=nil and x2~=nil and y2~=nil then
local angleInDegrees = (math.deg(math.atan2( (y2-y1), (x2-x1))))
return angleInDegrees
else
return 0
end
end
Hope that helps, Greg
I got it, it goes like a charm! I had the wrong approach…
I added this to my code to make it works every additional move:
if (player.rotation > 180)
player.rotation = player.rotation -360
elseif (player.rotation < -180) then
player.rotation = player.rotation - 360
end
Thank you very much Greg!
If you horizontally flip it (set xScale negative) won’t it rotate the other way round ?