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gigbig

BlitMask + rotation

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Hi, I am trying to create a smooth scroll effect: I have a wall that moves horizontally, and I am using 3 pieces with the old-school method. While shifting the wall rotates from x to y degrees. The result is ok, but I want to maximize performances: can I use BlitMask to create a shifting+rotating wall?

Is it correct to create the BlitMask for an item, add the item to a DisplayObject, and rotate the DisplayObject?

It seems to work ok, even if there is a minor glitch on the top side of the wall, showing the lowest pixels of the wall BMP and certain angles of the rotation (fixable with wrapOffsetY I suppose).

 

Thanks

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I don't think I'm visualizing the shifting rotating wall properly.

It doesn't sound like its something that we had in mind when BlitMask was created. The point being if you are constantly rotating the target of the BlitMask or children of the target, the BlitMask will constantly have to recapture the pixels of the target and run and update() which won't be terribly efficient. 

 

 

 

Again, I'm not quite following exactly what you want to accomplish.

I'm not sure if you should be rotating the content of the BlitMask (probably not) or a child of the BlitMask for the effect you want. 

 

I would suggest starting with a very basic BlitMask implementation and see how far you can take it. 

 

Perhaps once you have something in place we can take a peek and better assess the situation.

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Well, the solution I adopted seems to work great:

- I instantiated a piece of the wall to scroll

- I instantiated a blitmask with the wall as target, and enabled the wrap and autoupdate properties

- I added the target to a container displayObject

- I tweened the container to rotate

- I tweened the wall (the blitmask target) to scroll horizontally

 

The result is that the wall AND the blitmask rotate with the container.

Is this an unexpected result? Well, I thought it was not possible, but I tried and it worked... and it looks pretty smooth too.

What do you think Carl?

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Glad to hear it worked. Thanks for posting the results.

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But do you think it is an unexpected behaviour? Or do you think it shouldn't be used that way? I thought BlitMask could work with straight rectangles only, but this result tells the opposite.

 

the code is this:

private var blitMaskWall : BlitMask;
private var wallBM : Bitmap;
wallBM = new Bitmap(new PatternWall(), "auto", false);
blitMaskWall = new BlitMask( wallBM, wallBM.x, wallBM.y, wallBM.width*3, wallBM.height, false, true, 0x00000000, true);
blitMaskWall.wrapOffsetY = 1; //to avoid the wrap glitch with rotation
container.addChild(wallBM);
TweenLite.to(container, 10, {rotation: 60, onUpdate:***} );
...onUpdate:
wallBM.x -= wallShift;

I didn't expect the blitmask rotated with the target, but it does.

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From what I gather, everything is working exactly as it should. The BlitMask is just a Sprite that always sits in the same container as the target, and serves as a rectangular mask. So if you rotate the parent/container, yes, everything would rotate because it's all inside there (including the BlitMask Sprite). 

 

(or maybe I'm misunderstanding your question?)

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Uh, ok, so it is the right behaviour: I thought that BlitMask was constrained to straight rectangles, and that it couldn't be rotated because of limitations to regular (not rotated) memory areas.

Ok, I misunderstood, maybe because I have never seen an example with a rotated BlitMask.

This is a very good news because it opens new perspectives for my projects! Thank you Carl and Jack!

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