How to lerp properly from 350 degrees to 5 degrees?

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Golelorn

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Posted: 1st Jul 2019 22:22

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I've run into a problem using lerp.

Works fine unless I go from the high 300s to 5 degrees. You might see where this is going... The object will rotate counter clockwise once it makes the jump from 359 to 0 degrees. It then gets stuck in a loop.

Any guidance on how to handle this?

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fubarpk

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Posted: 1st Jul 2019 22:32

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have you got some example code ?

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Virtual Nomad

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Posted: 1st Jul 2019 22:39

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if you're comparing 2 wrapped angles to decide which way to rotate, try adding 360 to both, then compare.

otherwise, yeah, we need to know more about what you're trying to achieve.

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Golelorn

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Posted: 1st Jul 2019 22:51

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Sorry, I solved it. I eneded up using the quaternion commands, instead of the angles.

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Phaelax

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Posted: 2nd Jul 2019 01:54

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This has been asked a few times and I posted a solution in one of them a month or so ago

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Golelorn

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Posted: 2nd Jul 2019 19:03

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Well, the quats didn't work - the object would phase in and out occasionally. I couldn't find the thread you were referring to, Phaelex. I ended up doing this. Seems to work so far.

+ Code Snippet

	currentangle# = cos(GetObjectAngleY(EU.ID))
	SetObjectLookAt(EU.ID,EU.path.currentVector.x,EU.pos.y,EU.path.currentVector.z,0)
	angle#=WrapAngle(GetObjectAngleY(EU.ID)+180)
	EU.path.angle#=cos(angle#)
	newangle# = CurveValue(EU.path.angle#,currentangle#,6)
	if angle# >=180 and angle#<=360 
		newangle# = 360-acos(newangle#)
	else
		newangle# = acos(newangle#)
	endif
	SetObjectRotation ( EU.ID, 0, newangle#, 0 )

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Raven

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Posted: 3rd Jul 2019 01:04

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+ Code Snippet

Function Wrap( In As Float, Range As Float )
	Local Out As Float
	Local isNeg As Integer
	
	If In < 0.0 Then isNeg = 1
	In = Abs(In)
	Out = Range * ( ( In / Range ) - ( In Fmod Range ) )
	
	If isNeg Then Out = Out - (Out * 2) 
EndFunction Out

It's a bit derpy code as I'm tired as heck right now., but for Degrees use 360.0 as the Range; and Radians use PHI (3.142...)
As I recall I had something not too dissimilar for a Gimble/Eular Lock hack in DBP., but of course it's better use to Matrix Rotation (Quaternions) to resolve such issues.
Don't know why AppGameKit doesn't have built-in Matrix Support like DBP, and it's Vector Support is a bit "Meh" but you can always manually create such with Arrays and Types.

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blink0k

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Posted: 3rd Jul 2019 02:44

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You could use tweens. That way you get timer based movement rather than frame based movement.
Couple of things to remember;
You need to use -180 through180 to represent your angles (or 0 through 360 if your going the other way)
You also need to add UpdateAllTweens(GetFrameTime()) before Sync()

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Golelorn

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Posted: 3rd Jul 2019 03:32

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Oh, wow. Nice, blink0k. I had no idea those existed! I will look into that.

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blink0k

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Posted: 3rd Jul 2019 05:48

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Make the second angle larger (Add 360 if smaller) than the first angle to rotate clockwise
Make the first angle larger (Add 360 if smaller) than the second angle to rotate counter clockwise

That seemed to work for me

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Phaelax

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Posted: 4th Jul 2019 00:46 Edited at: 4th Jul 2019 00:47

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See if this fits what you want. (replace with whatever image)

// load the sprite
thing = createsprite(loadimage("robo4.png"))

// center sprite on the screen
thingX = getSpriteWidth(thing) / 2
thingY = getSpriteHeight(thing) / 2
setSpriteOffset(thing, thingX, thingY)
SetSpritePositionByOffset(thing, getVirtualWidth()/2, getVirtualHeight()/2)

originalAngle# = getSpriteAngle(thing) // 0 by default

do
	
	if getPointerState() = 1
		if rotateFlag = 0
			rotateFlag = 1
			
			// offset angle from where sprite is in relation to where mouse was clicked
			dx = getPointerX()-getSpriteXByOffset(thing)
			dy = getPointerY()-getSpriteYByOffset(thing)
			angle# = atanfull(dx, dy)
			offsetAngle# = angle# - getSpriteAngle(thing)
		else
			dx = getPointerX()-getSpriteXByOffset(thing)
			dy = getPointerY()-getSpriteYByOffset(thing)
			angle# = atanfull(dx, dy) - offsetAngle#
			setSpriteAngle(thing, angle#)
		endif
	else
		rotateFlag = 0
		a# = getSpriteAngle(thing)
		if a# > originalAngle#
			dec a#, 2
			if a# < originalAngle# then a# = originalAngle#
			setSpriteAngle(thing, a#)
		endif
	endif
	
	
	
	
	
	sync()
loop

+ Code Snippet

// load the sprite
thing = createsprite(loadimage("robo4.png"))

// center sprite on the screen
thingX = getSpriteWidth(thing) / 2
thingY = getSpriteHeight(thing) / 2
setSpriteOffset(thing, thingX, thingY)
SetSpritePositionByOffset(thing, getVirtualWidth()/2, getVirtualHeight()/2)

originalAngle# = getSpriteAngle(thing) // 0 by default






do
	
	if getPointerState() = 1
		if rotateFlag = 0
			rotateFlag = 1
			
			// offset angle from where sprite is in relation to where mouse was clicked
			dx = getPointerX()-getSpriteXByOffset(thing)
			dy = getPointerY()-getSpriteYByOffset(thing)
			angle# = atanfull(dx, dy)
			offsetAngle# = angle# - getSpriteAngle(thing)
		else
			dx = getPointerX()-getSpriteXByOffset(thing)
			dy = getPointerY()-getSpriteYByOffset(thing)
			angle# = atanfull(dx, dy) - offsetAngle#
			setSpriteAngle(thing, angle#)
		endif
	else
		rotateFlag = 0
		a# = getSpriteAngle(thing)
		if a# > originalAngle#
			dec a#, 2
			if a# < originalAngle# then a# = originalAngle#
			setSpriteAngle(thing, a#)
		endif
	endif
	
	
	
	
	
	sync()
loop

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