OpenGL ES 异步纹理加载

Question

简单的问题，是否可以使用 iOS 和 OpenGL ES 异步加载纹理？

这是我的加载方法，在单独的线程上调用：

//Image size
GLuint width = CGImageGetWidth(image.CGImage);
GLuint height = CGImageGetHeight(image.CGImage);

//Create context
void *imageData = malloc(height * width * 4);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(imageData, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);

//Prepare image
CGContextClearRect(context, CGRectMake(0, 0, width, height));
CGContextDrawImage(context, CGRectMake(0, 0, width, height), image.CGImage);

//Dispatch OpenGL stuff on main thread
dispatch_sync(dispatch_get_main_queue(), ^{
    //Bind texture
    glBindTexture(GL_TEXTURE_2D, name);

    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);

    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
});

//Release
CGContextRelease(context);
free(imageData);

如果我不在主线程上调度 OpenGL 调用，我的纹理将不会显示...

glDeleteTextures 调用的相同问题...

有什么想法吗？

Answer 1

您需要在后台线程上使用与主线程相同的上下文。为此使用setCurrentContext:。 所以在主线程上创建新线程（例如最简单的方法）并传递主上下文

[self performSelectorInBackground: @selector(loadTextureWithContext:) withObject: [EAGLContext currentContext]];

以及创建代码：

-(void) loadTextureWithContext:(EAGLContext*) main_context {
    [EAGLContext setCurrentContext: main_context];

    //Image size
    GLuint width = CGImageGetWidth(image.CGImage);
    GLuint height = CGImageGetHeight(image.CGImage);

    //Create context
    void *imageData = malloc(height * width * 4);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(imageData, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);

    //Prepare image
    CGContextClearRect(context, CGRectMake(0, 0, width, height));
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), image.CGImage);

    //Bind texture
    glBindTexture(GL_TEXTURE_2D, name);

    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);

    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    //Release
    CGContextRelease(context);
    free(imageData);

    [EAGLContext setCurrentContext: nil];
}

作为一个选项，您还可以创建新上下文并与主上下文共享相同的EAGLSharegroup。