Question

我通过将SDK提供的OpenGL上下文（EAGLContext）与SceneKit的SCNRenderer实例相结合，成功地将Vuforia SDK Image Target Tracking feature集成到iOS项目中。这使我能够利用SceneKit的3D API的简单性，同时又受益于Vuforia的高精度图像检测。现在，我想通过用Metal替换OpenGL来做同样的事情。

一些背景故事

我能够使用 OpenGL 在Vuforia绘制的实时视频纹理上绘制SceneKit对象，而不会出现重大问题。

这是我与 OpenGL 一起使用的简化设置：

func configureRenderer(for context: EAGLContext) {
    self.renderer = SCNRenderer(context: context, options: nil)
    self.scene = SCNScene()
    renderer.scene = scene

    // other scenekit setup
}

func render() {
    // manipulate scenekit nodes

    renderer.render(atTime: CFAbsoluteTimeGetCurrent())
}

Apple在iOS 12上弃用OpenGL

自Apple announced that it is deprecating OpenGL on iOS 12起，我认为尝试迁移此项目以使用Metal而不是OpenGL是一个好主意。

这在理论上应该很简单，因为Vuforia支持开箱即用的Metal。但是，当尝试将其集成时，我遇到了麻烦。

问题

该视图似乎只渲染SceneKit渲染器的结果或由Vuforia编码的纹理，而不会同时渲染两者。这取决于首先编码的内容。我该怎么做才能将两个结果融合在一起？

简而言之，这是有问题的设置：

func configureRenderer(for device: MTLDevice) {
    let renderer = SCNRenderer(device: device, options: nil)
    self.scene = SCNScene()
    renderer.scene = scene

    // other scenekit setup
}

func render(viewport: CGRect, commandBuffer: MTLCommandBuffer, drawable: CAMetalDrawable) {
    // manipulate scenekit nodes

    let renderPassDescriptor = MTLRenderPassDescriptor()
    renderPassDescriptor.colorAttachments[0].texture = drawable.texture
    renderPassDescriptor.colorAttachments[0].loadAction = .load
    renderPassDescriptor.colorAttachments[0].storeAction = .store
    renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColor(red: 0.0, green: 0, blue: 0, alpha: 0)

    renderer!.render(withViewport: viewport, commandBuffer: commandBuffer, passDescriptor: renderPassDescriptor)
}

我尝试在render之后或encoder.endEncoding之前致电commandBuffer.renderCommandEncoderWithDescriptor：

metalDevice = MTLCreateSystemDefaultDevice();
metalCommandQueue = [metalDevice newCommandQueue];
id<MTLCommandBuffer>commandBuffer = [metalCommandQueue commandBuffer];

//// -----> call the `render(viewport:commandBuffer:drawable) here <------- \\\\

id<MTLRenderCommandEncoder> encoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];

// calls to encoder to render textures from Vuforia

[encoder endEncoding];

//// -----> or here <------- \\\\

[commandBuffer presentDrawable:drawable];
[commandBuffer commit];

在任何一种情况下，我只能看到SCNRenderer的结果encoder OR ，但在同一视图中却看不到两者。

在我看来，上面的编码和SCNRenderer.render都覆盖了彼此的缓冲区。

我在这里想念什么？

Answer 1

我想我已经找到了答案。我在 endEncoding 之后渲染 scnrenderer ，但是我正在创建一个新的描述符。

    // Pass Metal context data to Vuforia Engine (we may have changed the encoder since
    // calling Vuforia::Renderer::begin)
    finishRender(UnsafeMutableRawPointer(Unmanaged.passRetained(drawable!.texture).toOpaque()), UnsafeMutableRawPointer(Unmanaged.passRetained(encoder!).toOpaque()))
    
    // ========== Finish Metal rendering ==========
    encoder?.endEncoding()
    
    // Commit the rendering commands
    // Command completed handler
    commandBuffer?.addCompletedHandler { _ in self.mCommandExecutingSemaphore.signal()}
    let screenSize = UIScreen.main.bounds.size
    let newDescriptor = MTLRenderPassDescriptor()
    
    // Draw to the drawable's texture
    newDescriptor.colorAttachments[0].texture = drawable?.texture

    // Store the data in the texture when rendering is complete
    newDescriptor.colorAttachments[0].storeAction = MTLStoreAction.store
    // Use textureDepth for depth operations.
    newDescriptor.depthAttachment.texture = mDepthTexture;
    renderer?.render(atTime: 0, viewport: CGRect(x: 0, y: 0, width: screenSize.width, height: screenSize.height), commandBuffer: commandBuffer!, passDescriptor: newDescriptor)
    
    // Present the drawable when the command buffer has been executed (Metal
    // calls to CoreAnimation to tell it to put the texture on the display when
    // the rendering is complete)
    commandBuffer?.present(drawable!)
    
    // Commit the command buffer for execution as soon as possible
    commandBuffer?.commit()

如何将SCNRenderer与现有的MTLCommandBuffer结合使用？

1 个答案: