[BUG] TweenChains not delaying correctly

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Scraggle

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Joined: 10th Jul 2003

Location: Yorkshire

Posted: 10th Apr 2015 13:21

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In the simple test below, there are two tweens in a chain.
They are both identical - they fade in a sprites alpha value from 0 to 255 over a period of 1 second.
When the first tween is complete, there is a 2 second delay before the second tween is carried out, so you would expect the sprite to remain fully opaque for those 2 seconds.
However, as you will see when you run the code, the sprite becomes fully transparent as soon as the first tween has finished.

+ Code Snippet

SetWindowSize( 300, 300, 0 )
SetVirtualResolution( 300, 300 )


CreateSprite( 1, 0 )
SetSpritePosition( 1, 100, 100 )
SetSpriteSize( 1, 100, 100 )

tween1 = CreateTweenSprite( 1 )
SetTweenSpriteAlpha( tween1, 0, 255, TweenLinear() )

tween2 = CreateTweenSprite( 1 )
SetTweenSpriteAlpha( tween2, 0, 255, TweenLinear() )

chain = CreateTweenChain()
AddTweenChainSprite( chain, tween1, 1, 0 )
AddTweenChainSprite( chain, tween2, 1, 2 )


do
	UpdateTweenChain( chain, GetFrameTime() )
	
    if GetPointerPressed()
		PlayTweenChain( chain )
	endif

    Sync()
loop

If you increase the delay on the first tween, the sprite disappears the moment the chain is played and doesn't wait for the delay to have passed.

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Scraggle

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Joined: 10th Jul 2003

Location: Yorkshire

Posted: 10th Apr 2015 13:26

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It seems it isn't just SpriteAlpha that performs like this. I've just tested the code below which moves the sprite, and again, it seems to jump to it's start value before the delay has passed.

+ Code Snippet

SetWindowSize( 300, 300, 0 )
SetVirtualResolution( 300, 300 )


CreateSprite( 1, 0 )
SetSpritePosition( 1, 100, 100 )
SetSpriteSize( 1, 100, 100 )

tween1 = CreateTweenSprite( 1 )
SetTweenSpriteX( tween1, 50, 150, TweenLinear() )
//SetTweenSpriteAlpha( tween1, 0, 255, TweenLinear() )

tween2 = CreateTweenSprite( 1 )
SetTweenSpriteX( tween2, 200, 100, TweenLinear() )
//SetTweenSpriteAlpha( tween2, 0, 255, TweenLinear() )

chain = CreateTweenChain()
AddTweenChainSprite( chain, tween1, 1, 2 )
AddTweenChainSprite( chain, tween2, 1, 2 )


do
	UpdateTweenChain( chain, GetFrameTime() )
	
    if GetPointerPressed()
		PlayTweenChain( chain )
	endif

    Sync()
loop

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BatVink

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Joined: 4th Apr 2003

Location: Gods own County, UK

Posted: 10th Apr 2015 14:30

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I agree, your code is fine and it's doing the same here (2.0.12)

I had the same quandary when I made my own animation/tween system (using the Berps and Lerps you posted many years ago

). Do you set the object to the start point immediately, or when the animation/tween starts? I did it the way you are expecting it to work, and set my objects manually to transparent if it was needed.

It could also be valid to set it the way it works here on a single-tween basis, but when you then create a chain the system falls apart.

If it is by design and won't be changed, then you need to create a dummy tween that goes from 255 to 255, and use that instead of a delay in the chain.

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Scraggle

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Joined: 10th Jul 2003

Location: Yorkshire

Posted: 10th Apr 2015 17:12

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I don't think it is a problem with the tweening algorithms. As you say, they work perfectly when they are not in a chain.
The issue is caused by the chain setting the start attributes of a tween before the time that it should start (according to the delay parameter).
That's something that only Paul could fix but I do like your workaround of creating a dummy tween that occupies the time of the delay.

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