iOSで複数のコンテキスト間でOpenGL ESオブジェクトを共有する

// コンテクストのリソースを取得する
- (void)initOpenGL {

    if ([EAGLContext currentContext]==nil) {
        context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    }
    else{
        context = [[EAGLContext alloc] initWithAPI:[[EAGLContext currentContext] API] sharegroup: [[EAGLContext currentContext] sharegroup]];
    }
	if (!context || ![EAGLContext setCurrentContext:context]) {
		return;
	}
	
	// ... (略)
	
}

Reference:
https://developer.apple.com/library/ios/qa/qa1612/_index.html
https://developer.apple.com/library/ios/documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/WorkingwithOpenGLESContexts/WorkingwithOpenGLESContexts.html
https://developer.apple.com/jp/documentation/OpenGLES_ProgrammingGuide.pdf