Loading a texture atlas only once

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Loading a texture atlas only once

(31 posts) (13 voices)

Started 2 years ago by nathan
Latest reply from Tanner85

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nathan
Member

Up to this point I've been loading my texture atlas in a few different objects, and reading Daniel's blog post on the subject, it sounds like I should only do this one.

What I'm trying to figure out, is what's a good way to deal with passing that reference around? I'm trying to avoid every object I create needing an initWithAtlas or whatever.

One thought was putting it as a property on the ApplicationDelegate, but that seemed a little messy and it was my first time trying to do that (new to iphone dev) plus not sure it logically belongs there? Thanks!

Posted 2 years ago #
matt62king
Member

I use a class that is a singleton instance. It manages my texture atlas and other objects that are used throught my game. This method has worked well for me.

Posted 2 years ago #
Daniel
Primary Feather
I also opt for either a singleton or a static class. In PenguFlip, I created a class called "Media", which had static methods for access to textures and sound. At the start of the game, I would call
```
[Media initTextures];
[Media initSound];
```
Then, wherever I need access to a texture or play a sound,
```
SPTexture *texture = [Media atlasTexture:@"button"];
[Media playSound:@"click.caf"];
```
and at the end, release all data.
```
[Media releaseTextures];
[Media releaseSound];
```
That worked fine for me. You are perfectly right, using static or global objects is always a sign for "code smell", and you should avoid it wherever possible. But in some cases, it makes sense. Here, it does, I think -- as the class acts as a read-only container for all media files.

Daniel
Posted 2 years ago #
nathan
Member

I was a little less familiar with singletons, so I opted for a "Media" class with static methods like you suggested Daniel. Works great!

Posted 2 years ago #
Kayhan
Moderator

I can't seem to find any definitive starts on how exactly to create such a class. Static methods seem simpler. If any of you could point me in the right direction it would be very helpful. Thanks.

Posted 1 year ago #
Daniel
Primary Feather

Kayhan, static methods are indeed simpler, so just use them -- I do so, too =)
I use singletons only very rarely. This design pattern is more useful in languages where you cannot create static methods, or when you need to have an object that can be passed along.

Posted 1 year ago #

enbr
Moderator

Kayhan, to create a static method for example, where you put this:

- (void)addSound:(SPSound *)sound key:(NSString *)key

Put this instead.

+ (void)addSound:(SPSound *)sound key:(NSString *)key

Then you can call it without allocating and initializing like this:

SPSound *buttonClick = [SPSound soundWithContentsOfFile:@"click.caf"];
[SoundManager addSound:buttonClick];

Posted 1 year ago #

qoolbox
Member

I know there is thread necromancy here but... daniel can you share your Media class?

Posted 1 year ago #

Daniel
Primary Feather

Sure, no problem! I plan to write a blog entry about this topic which explains it in more detail, but here is how the class looks like:

Media.h:

@interface Media : NSObject 
 
+ (void)initTextures;
+ (void)releaseTextures;
+ (SPTexture *)atlasTexture:(NSString *)name;
 
+ (void)initAudio;
+ (void)releaseAudio;
 
+ (void)playSound:(NSString *)soundName;
+ (SPSoundChannel *)soundChannel:(NSString *)soundName;
 
@end

Media.m:

#import "Media.h"
 
@implementation Media
 
static SPTextureAtlas *atlas = NULL;
static NSMutableDictionary *sounds = NULL;
 
#pragma mark Texture Atlas
 
+ (void)initTextures
{
    [atlas release];
    atlas = [[SPTextureAtlas alloc] initWithContentsOfFile:@"textures.xml"];
}
 
+ (void)releaseTextures
{
    [atlas release];
    atlas = nil;
}
 
+ (SPTexture *)atlasTexture:(NSString *)name
{
    if (!atlas)
        [NSException raise:NSGenericException format:@"call 'initTextures:' first"];
    return [atlas textureByName:name];
}
 
#pragma mark Audio
 
+ (void)initAudio
{
    if (sounds) return;
 
    [SPAudioEngine start];
    sounds = [[NSMutableDictionary alloc] init];
 
    // enumerate all sounds
 
    NSString *soundDir = [[NSBundle mainBundle] resourcePath];
    NSDirectoryEnumerator *dirEnum = [[NSFileManager defaultManager] enumeratorAtPath:soundDir];   
 
    NSString *filename;
    while (filename = [dirEnum nextObject])
    {
        if ([[filename pathExtension] isEqualToString: @"caf"])
        {
            SPSound *sound = [[SPSound alloc] initWithContentsOfFile:filename];
            SPSoundChannel *channel = [sound createChannel];
            [sounds setObject:channel forKey:filename];
            [sound release];
        }
    }
}
 
+ (void)releaseAudio
{
    [sounds release];
    sounds = nil;
    [SPAudioEngine stop];
}
 
+ (void)playSound:(NSString *)soundName
{
    [[sounds objectForKey:soundName] play];
}
 
+ (SPSoundChannel *)soundChannel:(NSString *)soundName
{
    return [sounds objectForKey:soundName];
}
 
@end

It should be rather self-explanatory! At the start of your game, call the 2 init-methods to load all resources. Then access the textures and sounds by their names.

In this sample, I simply load all ".caf" files that are available. Furthermore, there are 2 methods to access sounds: one to play it right away, another method if you need to have an audio channel.

I hope that helps!

Posted 1 year ago #

ipadfan
Member

and at the end, release all data.

[Media releaseTextures];
[Media releaseSound];

Daniel, when you say "at the end", where do you mean?

Posted 1 year ago #
Daniel
Primary Feather

E.g. in the 'dealloc'-method of your game class or the application delegate!

Posted 1 year ago #
ipadfan
Member

I used the awesome script referenced here: http://forum.sparrow-framework.org/topic/sparrow-atlas-generator and created a texture atlas.

It looks like it might be too big because the images display as white boxes.

It is 4096x2048.

When I use less images, those images display properly.

What do people do in these situation? I don't have any natural division between the images that need to be on the screen at one time (although, of course, not all are on screen at once) so it's possible, even likely, I would have multiple textures in use at the same time if I had to split the images across textures.

Posted 1 year ago #
straydogstrut
Administrator

I haven't seen the white boxes yet, but my understanding from this response by Daniel is that texture atlases (and textures) are limited to 2048x2048 on iPhone4 and 1024x1024 on older models. You would have to use more than one atlases if you need extra sizes, although you may also want to look into tiling your SPimages as they describe. In this way, you can create larger levels where the tiles are replaced at either edge of the screen as you move around. It would depend what you're trying to do.

If I've made a mistake at all, Daniel please feel free to correct me. I've only just started using texture atlases myself!

Posted 1 year ago #
ipadfan
Member

Thanks -- I think knowing the limits I can get something together that'll work.

Posted 1 year ago #
Daniel
Primary Feather
Straydogstrut, your explanation was perfect, that's exactly the way it is!

BTW, there's a nice way to use the Media class from above with separate atlases -- at least if all the atlases fit into memory at once.

In the 'initTextures'-method, load all the atlases you need. Then, change the 'atlasTexture:'-method like this:
+ (SPTexture *)atlasTexture:(NSString *)name { SPTexture *texture = [atlas1 textureByName:name]; if (texture) return texture; texture = [atlas2 textureByName:name]; if (texture) return texture; // ... }
It's a bit of a hack, but it makes it extremely convenient to use, because you just ask for a texture with a certain name, without caring about the atlas it comes from.
Posted 1 year ago #
ipadfan
Member

Wow -- use of textures really improves the performance of an app. Thanks for all the contributors to this post (and others on the same topic). I encourage even beginners like me to work with the code posted above and the atlas generator that comes with Sparrow. Well worth it. Excellent.

Posted 1 year ago #
straydogstrut
Administrator

Straydogstrut, your explanation was perfect, that's exactly the way it is!

I had a great teacher;-)

I encourage even beginners like me to work with the code posted above and the atlas generator that comes with Sparrow. Well worth it.

I'm starting to appreciate the need for a seperate Media class so will definitely be implementing this approach this weekend. Thanks Daniel for explaining it as you have here, and a future blog post would be very welcome when you have the time.

Posted 1 year ago #
pixelrevision
Member
Most objective-c you will find tend to use singletons that wrap objects created with composition. So that the class that you access is a really light allocation (really just some pointers), and you can use the objects inside of it like any other class. You also give yourself the freedom to make multiple instances if needed:
[[MyGameAssets sharedInstance] getMedia];
I find this kind of approach very good when working with stuff like levels where as your game grows you may find yourself all of a sudden needing to load/unload in multiple sprite sheets and sounds. So media changes, but you still have a global access point to it.

An example of creating a singleton is very simple in objective-c:
static MyGameAssets *instance = NULL; + (MyGameAssets*)sharedInstance{ @synchronized(self){ if (instance == NULL){ instance = [[self alloc] init]; } } return(instance); }
Then write the class like as normal from there.

Anytime you want a reference to this class you just reference sharedInstance. So instead of:
MyGameAssets *ga = [[MyGameAssets alloc] init];
You use:
MyGameAssets *ga = [MyGameAssets sharedInstance];
The static approach is very valid, but I just wanted to post an alternative in case people see this post in a search later.
Posted 1 year ago #
Daniel
Primary Feather

Pixelrevision, thanks for adding the Singleton approach here! That's of course a great alternative.

Posted 1 year ago #
straydogstrut
Administrator
I've started porting over some of my code to use the Media class described by Daniel. It works great and I was surprised how straightforward it is. I've run into a problem however: how would I use the above approach where I need to pull frames from an atlas using texturesStartingWith? I'm using this to populate a move clip with frames for my main character's animation.

The current method accepts a string, however I only have the first part of this string. Of course I *do* know the full texture name, but i've been using this method for its flexibility (being able to easily add more frames is one reason). Really I need a reference to the texture atlas itself, so i've considered adding another method just to return the texture atlas, but I think that would defeat the point of using the Media class (not to mention I currently have more than one atlas, so i'd have to target the correct one) so instead i've tried to create a method within the Media class that gets the frames and returns them as an array to my game level. It compiles fine, but the app crashes with an 'empty texture array' error. Is this the right approach?

Media.m
+ (NSArray *)movieFrames:(NSString *)name { NSArray *frames = [atlas1 texturesStartingWith:name]; if (frames){ return frames; } frames = [atlas2 texturesStartingWith:name]; if (frames){ return frames; } return 0; }
Player.m
//SPTextureAtlas *atlas = [SPTextureAtlas atlasWithContentsOfFile:@"spencer.xml"]; // add frames to movie //NSArray *frames = [atlas texturesStartingWith:@"spencer_"]; //NSArray *frames = [Media movieFrames:@"spencer_"]; //<-- moved this straight into the line below mMovie = [[SPMovieClip alloc] initWithFrames:[Media movieFrames:@"spencer_"] fps:6];
I've left my commented lines in so you can see my previous approach (which worked fine). I have to get up early for work so will have to leave this until tomorrow evening, but if there's a glaring flaw in my approach, i'd appreciate any pointers. Thank you.
Posted 1 year ago #

Daniel
Primary Feather

Hi straydogstrut,

your approach is great -- it's just one little detail that causes it to fail. When the atlas does not contain any texture starting with a certain name, it does not return 'nil', but an empty array. With that knowledge, it's easy to fix your method:

+ (NSArray *)movieFrames:(NSString *)name
{
    NSArray *frames = [atlas1 texturesStartingWith:name];
    if (frames.count > 0)
        return frames;    
 
    frames = [atlas2 texturesStartingWith:name];
    if (frames.count > 0)
        return frames;
 
    return nil;
}

I hope that helps!

Posted 1 year ago #

straydogstrut
Administrator

Thank you for this Daniel, makes perfect sense.

-Daniel

Posted 1 year ago #
dprijadi
Member

^_^ media class should be know to everyone who use sparrow

another code snippet destined for Sparrow Wiki imho

Posted 10 months ago #
dprijadi
Member

dear daniel

whats the advantage/disadvantage of your media class over the singleton approach by pixelrevision ?

is it the same ? or singleton is better ?

regards

Posted 10 months ago #
dprijadi
Member

-_-' double post

Posted 10 months ago #
Shilo
Master Sparrow

I prefer using class methods (Daniels approach) instead of a Singleton. But there is very little difference overall. With class methods, you are forced to use static variables instead of member variables, and you also won't be able to use properties.

I do remember running into a variable issue where I should have used a singleton instead of class methods, I actually discussed it with Pixelrevision. I wish I could remember what exactly was the issue.

In short, I think Singletons can give you more flexibility, while class methods are easier to implement.

Posted 10 months ago #
Daniel
Primary Feather

There's nothing I could add to your description, Shilo!

Posted 10 months ago #
Daniel
Primary Feather

I added the code to the wiki!

Posted 10 months ago #
dprijadi
Member

thanks for the clarification shilo and daniel !! and the wiki update too =D

Posted 10 months ago #
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Unregistered

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Posted 10 months ago #

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