I'm doing an animation class in ActionScript 3 and would like to know the most efficient way to do it.
Currently what I do is get an image (sprite sheet) and keep all the frames in an array of Bitmaps, then add each frame as a child and I put setVisible = false except the frame I have to show.
The other way I can think of is to have only one Bitmap added as a child and every time frame has to be changed, I copy the pixels to the Bitmap using copyPixels function.
There is somewhat more efficient than either of these alternatives?
Thanks
Keep all your frames in a vector of BitmapData. Then use a single Bitmap and change it's bitmapData property when you want to change frames.
Copypixels is quite fast.
There's an excellent comparison of rendering methods here at 8bitrocket.com; I would suggest giving it a read.
Related
I am making a game in AS3 for a school project (using the AIR api). I have about a year's worth of experience in AS3, so i would say i'm proficient but not an expert. Anyway, i have never attempted to do sprite animations in AS3 and i'm not quite sure how to approach it.
If i create a list of bitmaps and call addChild() and removeChild() to display each frame of the animation, it would affect the framerate as these functions are not very efficient (i have tried this before and it tanked my framerate if i had too many animations going at once). I have also tried creating a list of BitmapData objects, adding a bitmap to the display list, and then pointing it to a different BitmapData each frame, but this does not seem to work at all.
So what is the best way to do this? In XNA, for example, i would create a sprite class that draws to the screen using a sprite batch, then i would create a list of sprite objects and cycle through them to create the animation. Is there any way to achieve a similar result in actionscript?
First (simple) method: you can just use multi-frame MovieClip for animation. Put an image in each frame, put a MovieClip on the stage and that's all. You can control this animation using play(), stop(), gotoAndPlay(), gotoAndStop(). It will work without much problems for a generic platform game (I did that myself long ago).
Second (advanced) method: use bitmap blitting. For each animation, create a bitmap image that holds each frame of the animation. Use this image as a source for copying pixels into your current animated object. You just need to copy a particular rectangle area inside a source bitmap that corresponds to the current frame.
The actual blitting happens here
destinationBitmapData.copyPixels(sourceBitmapData, areaRectangle, destinationPoint);
Where destinationBitmapData is your "canvas" that you're blitting to; sourceBitmapData is the source image holding all animation frames; areaRectangle is the Rectangle inside the source image defining which area to copy; destinationPoint is left-top coordinate of the copy area in your canvas.
The destination canvas can be just one small object (like your game character that is moving around) or the entire game screen with all objects. I.e. instead of blitting and adding each object separately, you can just have one big canvas and blit any necessary parts directly to it.
That said, there is already a number of various ready-made engines that use blitting and even advanced techniques like 3D acceleration for 2D sprites.
One of them is Starling.
I'm currently doing the following when applying a mask to a MovieClip:
mc1.cacheAsBitmap = true;
_mask.cacheAsBitmap = true;
mc1.mask = _mask;
Which works great, however...
mc1 is a complex vector animation, and cacheing it as a bitmap in order to mask it has pretty big memory implications from what I can see, and have read.
Is their another way to implement masks? Or a way to optimise the usual solution?
Thanks
edit
Both the mask and mc1 are MovieClips, and they have been added to the stage, the mask is a gradient.
I am using Flash CS6, both movieclip and mask are added to the timeline, where they are being animated
You can use http://www.greensock.com/blitmask/
Quote from the documentation:
Can’t I just set the target DisplayObject’s cacheAsBitmap property to true and get the same result? Why use BlitMask?
If you set a DisplayObject’s cacheAsBitmap property to true, Flash takes a bitmap capture of that object so that when you move it (only
altering the x and/or y properties), the text and vectors don’t need
to be re-rasterized again before being rendered to the screen.
However, Flash would still need to concern itself with extra pixels on
every frame if you’re masking them to only show a small portion of the
area. BlitMask, however, only cares about that smaller masked area
(after the initial capture of course) which alleviates Flash from
having to even think about the extra pixels.
I'm making an animation of a 2D character that can walk, run, jump, bend,...
Would it be better to load one big 'spritesheet' with all the animations and just use a mask, or would loading separate files (walk, run,...) be better because you're not using a mask on such a big image every frame?
I'm not using the Stage3D features with a framework like Starling because I think the normal flash display API is fast enough and has much less bugs than the relatively new GPU frameworks.
Blitting just the character (using lock(),copyPixels(),unlock()) works pretty well.
private function updatePixels():void{
//update sprite sheet copy position based on the frame placements ons prite sheet
position.x = spriteSourceData[currentFrame].x + offset.x;
position.y = spriteSourceData[currentFrame].y + offset.y;
//draw into the bitmap displayed
displayData.lock();
displayData.fillRect(displayData.rect, 0x00FFFFFF);//clear
displayData.copyPixels(sourceData, spriteData[currentFrame], position);//copy new frame pixels
displayData.unlock();
}
//a bit about vars:
position:Point
spriteSourceData:Vector.<Rectangle> - from parsed Texture Packer data
offset:Point - front view and side view animations weren't always centred, so an offset was needed
displayData:BitmapData - pluging into a Bitmap object displayed
sourceData:BitmapData - the large sprite sheet
currentFrame:int - image index on the sprite sheet
I've done this on an older project writing a custom class loosely following what I've learned from Lee Brimelow's tutorial series Sprite Sheets and Blitting (Part 1,Part 2, Part 3)
In short, you'd use two BitmapData objects:
a large sprite sheet
a small image to display just the character (size of the largest character bounding box) to copy pixels into
In my project I had a character with front and side animations and for the sides I've used one set of animations and used the Matrix class to flip(scale and translate) the side animation accordingly. I've used TexturePacker to export the image sequence as a sprite sheet and the frame data as well as a JSON object. There is native JSON support now, so that's handy. Texture Packer isn't free but it's really worth the money (affordable, fast and does the job perfectly). I haven't used Flash CS6 yet but I imagine it's also possible to import your image sequence and export a spritesheet with the new feature.
In my experience the rule "the simpler the display list the better the performance" generally applies. Which means you should use the most specific display object that will do the job (don't use a Sprite when a Shape would be sufficient or favor Bitmaps over vectors where it makes sense).
The most extreme version of this is to only have one Bitmap display object on the stage and use copyPixels to draw all game objects into it every time you want to update the screen. It doesn't really matter what the source in the copyPixel call is, it could either be a large BitmapData acting as a sprite sheet or a small BitmapData objects representing a single frame in an animation. This method is really fast and you could easily have many hundreds of objects on screen at the same time. But using copyPixels means you can't scale or rotate a game object, so for those cases you would have to fall back to the much slower draw() method. Of course this single Bitmap method is not suitable for games where you need to attach mouse events to specfic objects in the game, but works well for shoot'em ups or platform games.
To answer your question, I think you will get better performance by using a single Bitmap display object to represent the player and a collection of BitmapData objects for all the animation frames. Then you can just change the Bitmap's bitmapData property to the frame you want to display. You can still load a large spritesheet png and then plit it up into a series of BitmapData objects during the initialization of the game.
There was many discussions about this problem, but I want to pay attention on the situations that IMHO seems not so clear:
Yes the general rules are:
Remove chachedAsBitmap
Stop movieClip if playing
Remove events
Delete references
etc.
But let's look:
First Example:
I have nested sprite (ex: mainSprite), it contains other sprites with dynamic textFields in it (and are chached as bitmaps), just textFileds and MovieClips with event listeners on it (with weak reference).
When I need to remove this sprite I need first to remove all it's nested content via loops or just
removeChild(mainSprite);
mainSprite=null;
is just enough?
Second Example:
I have some sprite in which I'm loading bitmap and manipulating with bitmapData, later I'm just replacing content of this sprite with another bitmap, is allocated memory for older bitmap automatically erases and is overwritten or it still exists?
Third example:
I have some "graphics template" MovieClip (in library with Export for Actionscript property set on it) which I'm adding on the stage and filling with dynamic data (and adding event listeners), let's say that it's one scene of the app, on another scene I need same MovieClip with other dynamic data, but inbetween need to clear my stage (need something like transition animation which is also library MovieClip), what's the best way: to set this MovieClip visible property to false (while transition animation is plays) and then reuse it, or just remove it with removeChild and then add when add with addChild once more?
All I wrote is more about Air Mobile, cause in most cases for the desktop these situations aren't so problematic, but in case of mobile development they are.
You can visually monitor memory usage along with fps etc using this lib: http://code.google.com/p/flash-console/
hope that helps.
P.S. gc in flash is always a weird thing :)
First example: removing mainSprite from display list is enough if there are only weak listeners on its children.
Second example: I'd advice reusing the same object with visible = false. Recreating the same object is more resource expensive plus you get another instance of the same thing being in memory before it gets gc'ed.
If I run cacheAsBitmap = true on a complex Sprite the caching can sometimes take up to a second.
Is there any way to check for when a DisplayObject has finished being cached?
Nope, there is no possible way. However, cacheAsBitmap is using a system of creating a Bitmap object under the hood. This bitmap gets drawn with the pixel information of the DisplayObject. Hence, if you desire a fine-grain control over how cacheAsBitmap works, I would say that you should instead use Bitmap/BitmapData directly, instead of using a Sprite/MovieClip with the cacheAsBitmap feature. Hope this helps!
This article should help you if you do not know how to work with Bitmaps:
http://www.flashgameblog.at/blog-post/2010/04/08/blitting-the-art-of-fast-pixel-drawing/