ios - 如何在 IOS 5 上更改图层的分辨率

Question

我正在 ios 5 上开发一个 opengl es 2.0 应用程序。我绘制一个纹理作为背景。当我旋转设备时，我需要旋转图层并更改图层的尺寸。问题是我可以更改图层的边界，但图层分辨率是相同的。我的意思是，如果我有一个边界为 1024*768 的图层，并且我将新图层边界定义为 768*1024，图层大小会发生变化，但是当我将 768*1024 纹理绘制为背景时，图像会变形。

我使用函数 canvasView.bounds = newCanvasRect; 和 canvasView.frame = newCanvasRect; 来更改图层大小(其中 canvasView 是图层，newCanvasRect 是新边界).

有什么想法吗？

Answer 1

每次设备旋转新的高度和宽度时，您都必须销毁并重建帧缓冲区。使用 layoutsubviews 触发所有这些，当方向改变时调用:

- (void)layoutSubviews {
   NSLog(@"layoutSubviews");
   [EAGLContext setCurrentContext:_context];
   [self destroyFramebuffer];
   [self createFramebuffer];
}


- (void)destroyFramebuffer {
   NSLog(@"destroy buffer");

   glDeleteFramebuffers(1, &viewFramebuffer);
   viewFramebuffer = 0;
   glDeleteRenderbuffers(1, &viewRenderbuffer);
   viewRenderbuffer = 0;
   glDeleteRenderbuffers(1, &depthRenderbuffer);
   depthRenderbuffer = 0;
}


- (BOOL)createFramebuffer {
   NSLog(@"creating buffer");

   glGenFramebuffers(1, &viewFramebuffer);
   glBindFramebuffer(GL_FRAMEBUFFER, viewFramebuffer);

   glGenRenderbuffers(1, &viewRenderbuffer);
   glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);

   // setup the renderbuffer to the context
   [[EAGLContext currentContext] renderbufferStorage:GL_RENDERBUFFER fromDrawable:(CAEAGLLayer *)self.layer];
   glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, viewRenderbuffer);

   // Allocate color buffer backing based on the current layer size (get the current layer size)
   glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &backingWidth);
   glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &backingHeight);

   NSLog(@"backing width: %d height: %d",backingWidth, backingHeight);

   // set up the depth buffer
   glGenRenderbuffers(1, &depthRenderbuffer);
   glBindRenderbuffer(GL_RENDERBUFFER, depthRenderbuffer);
   glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, backingWidth, backingHeight);
   glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthRenderbuffer);
   glEnable(GL_DEPTH_TEST);
   glEnable(GL_CULL_FACE);

   [self setupView];

   return YES;
}

然后使用 backingWidth 和 backingHeight 重新创建投影矩阵。