GLKTextureLoader fails when loading a certain text

问题:

I'm making an iPhone application with OpenGL ES 2.0 using the GLKit. I'm using GLKTextureLoader to load textures synchronously.

The problem is that for a certain texture, it fails to load it the first time. It gives this error:

The operation couldn’t be completed. (GLKTextureLoaderErrorDomain error 8.)

For this error code, the apple documentation says the following:

GLKTextureLoaderErrorUncompressedTextureUpload
An uncompressed texture could not be uploaded.
Available in iOS 5.0 and later.
Declared in GLKTextureLoader.h.

(not very much).

Could I be trying to load the texture while the opengl context is in some busy state or something like that?

Notes:

• Before getting to load this texture I load other textures and those work on the first try. Also, the exact same texture file will load ok on the second try.
• There should be enough free video memory as I have only a couple of textures loaded before this one.
• The texture is an uncompressed PNG with alpha, but I also tried with TGA (24bit & 32bit) with no luck.

Any ideas are welcomed, thanks

EDIT:

More info:

• the opengl context is shared between all my screens. I'm doing this to keep my shaders and textures loaded between screens.

• the problem above happens when I go to my second screen. In the first screen I draw textured stuff with no problems (other textures though).

• The problem above happens when I load my content (game entities) in the game world. Each entity tries to load the texture. I have a simple caching system that loads the texture only once and then returns the same id for all other entities. I'm loading the entities synchronously, in one method. The first entity fails to load the texture then comes the second and succeeds and then the third one gets the cached id.

• I am calling the load entities method in viewDidAppear and I've tried to add a sleep for 2 seconds before I load any entities but nothing changed.

EDIT:

Texture loading code:

- (GLKTextureInfo *)loadTextureAtPath:(NSString*)path ofType:(NSString*)type withKey:(NSString *)key 
{
    GLKTextureInfo* tex;

    tex = [self textureWithKey:key];
    if (tex)
        return tex;

    NSDictionary * options = [NSDictionary dictionaryWithObjectsAndKeys:
                              [NSNumber numberWithBool:NO],
                              GLKTextureLoaderOriginBottomLeft, 
                              nil];

    NSError * error;    
    NSString *bundlepath = [[NSBundle mainBundle] pathForResource:path ofType:type];

    tex = [GLKTextureLoader textureWithContentsOfFile:bundlepath options:options error:&error];
    if (tex == nil) 
        DLOG_LOCAL(@"Error loading texture: %@", [error localizedDescription]);                
    else
        [textures setObject:tex forKey:key];

    return tex;
}

回答1:

I was also getting

The operation couldn’t be completed. (GLKTextureLoaderErrorDomain error 8.)

when loading a texture late in runtime while several previous textures had loaded successfully closer to launch. I was able to solve the problem by inserting the following line of code before the GLKTextureLoader call:

NSLog(@"GL Error = %u", glGetError());

Sure enough, GL was reporting an error, but it did not require me to address the error in order for GLKTextureLoader to work. Merely getting the GL Error was enough.

回答2:

I got this when enabling textures before loading the texture. Simply moved glEnable(GL_TEXTURE) after the loading and the issue was gone.

回答3:

Maybe you've resolved this, but are you using multiple contexts? maybe you should be loading your texture asynchronously with sharegroup.

so instead of using tex = [GLKTextureLoader textureWithContentsOfFile:bundlepath options:options error:&error];

use something like:

GLKTextureLoader *textureloader = [[GLKTextureLoader alloc] initWithSharegroup:self.eaglContext.sharegroup];
GLKTextureInfo *myTexture;
[textureloader textureWithCGImage:_currentForegroundImage.CGImage options:nil queue:nil completionHandler:^(GLKTextureInfo *textureInfo, NSError *error) {
        myTexture = textureInfo;
        if(error) {
            // log stuff
        }
        // do something
}];

回答4:

I had a similar problem. Is was caused by a texture that had width / height not power of 2. GLKTextureLoader failed on loading this and the following images. Checking glGetError() after each texture load revealed the troublemakers :-).

回答5:

Ok, I'll try this one again as I ran into the error again. What appears to happen is that if there is some other glError that has not been processed, then you will have trouble with the texture loading on the first time.

Before you load that texture that fails, check for a glError and then track down where that error occurred. Or you can capture an opengl frame prior to where the texture is loaded and see if a glError is being thrown prior. This happened to me both times when I ran into the error 8, and both times this error disappeared once I fixed the error that had occurred earlier.

回答6:

I ran into the same problem. I'm not exactly sure as to why it occurred exactly other than that it appeared that there were multiple file operations going on at the same time. For example, performing a file load (for model data) right AFTER using the texture loader for the first time would cause error 8 to pop up. I fixed it in my program by having some other operations occur after the texture loader is called for the first time.

回答7:

I've also found that you get this error when trying to create a 2D texture with an image larger than the maximum texture size. For the max size you can see Apple's Open GL ES Platform Notes, although those do not appear correct for newer devices so the best bet is to get the value directly.

回答8:

I had very similar problem and it has been solved by calling setCurrentContext.

self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
[EAGLContext setCurrentContext:self.context];