作为主要的高级/iOS 开发人员，我对将 SceneKit 用于动画项目很感兴趣。
几个月来我一直很喜欢 SceneKit，尽管它显然是为“实时”交互而设计的，但我发现能够将 SKScene“渲染”到视频中非常有用。目前，我一直在使用 Quicktime 的屏幕录像机来捕捉视频输出，但是（当然）这样做会降低帧率。是否有替代方案可以让场景按照自己的节奏进行渲染并输出为流畅的视频文件？
我知道这不太可能......只是想我会问，以防我错过了一些较低级别的东西！
【问题讨论】：
标签： ios macos video rendering scenekit
您可以使用 SCNRenderer 渲染到屏幕外的 CGImage，然后使用 AVFoundation 将 CGImage 添加到视频流。
我编写了这个用于渲染成 CGImage 的 Swift 扩展。
public extension SCNRenderer {
public func renderToImageSize(size: CGSize, floatComponents: Bool, atTime time: NSTimeInterval) -> CGImage? {
var thumbnailCGImage: CGImage?
let width = GLsizei(size.width), height = GLsizei(size.height)
let samplesPerPixel = 4
#if os(iOS)
let oldGLContext = EAGLContext.currentContext()
let glContext = unsafeBitCast(context, EAGLContext.self)
EAGLContext.setCurrentContext(glContext)
objc_sync_enter(glContext)
#elseif os(OSX)
let oldGLContext = CGLGetCurrentContext()
let glContext = unsafeBitCast(context, CGLContextObj.self)
CGLSetCurrentContext(glContext)
CGLLockContext(glContext)
#endif
// set up the OpenGL buffers
var thumbnailFramebuffer: GLuint = 0
glGenFramebuffers(1, &thumbnailFramebuffer)
glBindFramebuffer(GLenum(GL_FRAMEBUFFER), thumbnailFramebuffer); checkGLErrors()
var colorRenderbuffer: GLuint = 0
glGenRenderbuffers(1, &colorRenderbuffer)
glBindRenderbuffer(GLenum(GL_RENDERBUFFER), colorRenderbuffer)
if floatComponents {
glRenderbufferStorage(GLenum(GL_RENDERBUFFER), GLenum(GL_RGBA16F), width, height)
} else {
glRenderbufferStorage(GLenum(GL_RENDERBUFFER), GLenum(GL_RGBA8), width, height)
}
glFramebufferRenderbuffer(GLenum(GL_FRAMEBUFFER), GLenum(GL_COLOR_ATTACHMENT0), GLenum(GL_RENDERBUFFER), colorRenderbuffer); checkGLErrors()
var depthRenderbuffer: GLuint = 0
glGenRenderbuffers(1, &depthRenderbuffer)
glBindRenderbuffer(GLenum(GL_RENDERBUFFER), depthRenderbuffer)
glRenderbufferStorage(GLenum(GL_RENDERBUFFER), GLenum(GL_DEPTH_COMPONENT24), width, height)
glFramebufferRenderbuffer(GLenum(GL_FRAMEBUFFER), GLenum(GL_DEPTH_ATTACHMENT), GLenum(GL_RENDERBUFFER), depthRenderbuffer); checkGLErrors()
let framebufferStatus = Int32(glCheckFramebufferStatus(GLenum(GL_FRAMEBUFFER)))
assert(framebufferStatus == GL_FRAMEBUFFER_COMPLETE)
if framebufferStatus != GL_FRAMEBUFFER_COMPLETE {
return nil
}
// clear buffer
glViewport(0, 0, width, height)
glClear(GLbitfield(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)); checkGLErrors()
// render
renderAtTime(time); checkGLErrors()
// create the image
if floatComponents { // float components (16-bits of actual precision)
// slurp bytes out of OpenGL
typealias ComponentType = Float
var imageRawBuffer = [ComponentType](count: Int(width * height) * samplesPerPixel * sizeof(ComponentType), repeatedValue: 0)
glReadPixels(GLint(0), GLint(0), width, height, GLenum(GL_RGBA), GLenum(GL_FLOAT), &imageRawBuffer)
// flip image vertically — OpenGL has a different 'up' than CoreGraphics
let rowLength = Int(width) * samplesPerPixel
for rowIndex in 0..<(Int(height) / 2) {
let baseIndex = rowIndex * rowLength
let destinationIndex = (Int(height) - 1 - rowIndex) * rowLength
swap(&imageRawBuffer[baseIndex..<(baseIndex + rowLength)], &imageRawBuffer[destinationIndex..<(destinationIndex + rowLength)])
}
// make the CGImage
var imageBuffer = vImage_Buffer(
data: UnsafeMutablePointer<Float>(imageRawBuffer),
height: vImagePixelCount(height),
width: vImagePixelCount(width),
rowBytes: Int(width) * sizeof(ComponentType) * samplesPerPixel)
var format = vImage_CGImageFormat(
bitsPerComponent: UInt32(sizeof(ComponentType) * 8),
bitsPerPixel: UInt32(sizeof(ComponentType) * samplesPerPixel * 8),
colorSpace: nil, // defaults to sRGB
bitmapInfo: CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue | CGBitmapInfo.FloatComponents.rawValue),
version: UInt32(0),
decode: nil,
renderingIntent: kCGRenderingIntentDefault)
var error: vImage_Error = 0
thumbnailCGImage = vImageCreateCGImageFromBuffer(&imageBuffer, &format, nil, nil, vImage_Flags(kvImagePrintDiagnosticsToConsole), &error)!.takeRetainedValue()
} else { // byte components
// slurp bytes out of OpenGL
typealias ComponentType = UInt8
var imageRawBuffer = [ComponentType](count: Int(width * height) * samplesPerPixel * sizeof(ComponentType), repeatedValue: 0)
glReadPixels(GLint(0), GLint(0), width, height, GLenum(GL_RGBA), GLenum(GL_UNSIGNED_BYTE), &imageRawBuffer)
// flip image vertically — OpenGL has a different 'up' than CoreGraphics
let rowLength = Int(width) * samplesPerPixel
for rowIndex in 0..<(Int(height) / 2) {
let baseIndex = rowIndex * rowLength
let destinationIndex = (Int(height) - 1 - rowIndex) * rowLength
swap(&imageRawBuffer[baseIndex..<(baseIndex + rowLength)], &imageRawBuffer[destinationIndex..<(destinationIndex + rowLength)])
}
// make the CGImage
var imageBuffer = vImage_Buffer(
data: UnsafeMutablePointer<Float>(imageRawBuffer),
height: vImagePixelCount(height),
width: vImagePixelCount(width),
rowBytes: Int(width) * sizeof(ComponentType) * samplesPerPixel)
var format = vImage_CGImageFormat(
bitsPerComponent: UInt32(sizeof(ComponentType) * 8),
bitsPerPixel: UInt32(sizeof(ComponentType) * samplesPerPixel * 8),
colorSpace: nil, // defaults to sRGB
bitmapInfo: CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue | CGBitmapInfo.ByteOrder32Big.rawValue),
version: UInt32(0),
decode: nil,
renderingIntent: kCGRenderingIntentDefault)
var error: vImage_Error = 0
thumbnailCGImage = vImageCreateCGImageFromBuffer(&imageBuffer, &format, nil, nil, vImage_Flags(kvImagePrintDiagnosticsToConsole), &error)!.takeRetainedValue()
}
#if os(iOS)
objc_sync_exit(glContext)
if oldGLContext != nil {
EAGLContext.setCurrentContext(oldGLContext)
}
#elseif os(OSX)
CGLUnlockContext(glContext)
if oldGLContext != nil {
CGLSetCurrentContext(oldGLContext)
}
#endif
return thumbnailCGImage
}
}
func checkGLErrors() {
var glError: GLenum
var hadError = false
do {
glError = glGetError()
if glError != 0 {
println(String(format: "OpenGL error %#x", glError))
hadError = true
}
} while glError != 0
assert(!hadError)
}
【讨论】：
** 这是使用 Metal 的 SceneKit 的答案。
** 警告：这可能不是 App Store 的正确方法。但它正在工作。
第1步：使用swizzling将CAMetalLayer的nextDrawable方法换成新的。 为每个渲染循环保存 CAMetalDrawable。
extension CAMetalLayer {
public static func setupSwizzling() {
struct Static {
static var token: dispatch_once_t = 0
}
dispatch_once(&Static.token) {
let copiedOriginalSelector = #selector(CAMetalLayer.orginalNextDrawable)
let originalSelector = #selector(CAMetalLayer.nextDrawable)
let swizzledSelector = #selector(CAMetalLayer.newNextDrawable)
let copiedOriginalMethod = class_getInstanceMethod(self, copiedOriginalSelector)
let originalMethod = class_getInstanceMethod(self, originalSelector)
let swizzledMethod = class_getInstanceMethod(self, swizzledSelector)
let oldImp = method_getImplementation(originalMethod)
method_setImplementation(copiedOriginalMethod, oldImp)
method_exchangeImplementations(originalMethod, swizzledMethod)
}
}
func newNextDrawable() -> CAMetalDrawable? {
let drawable = orginalNextDrawable()
// Save the drawable to any where you want
AppManager.sharedInstance.currentSceneDrawable = drawable
return drawable
}
func orginalNextDrawable() -> CAMetalDrawable? {
// This is just a placeholder. Implementation will be replaced with nextDrawable.
return nil
}
}
第 2 步： 在 AppDelegate 中设置 swizzling：didFinishLaunchingWithOptions
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
CAMetalLayer.setupSwizzling()
return true
}
第 3 步： 为您的 SCNView 的 CAMetalLayer 禁用 framebufferOnly（以便为 MTLTexture 调用 getBytes）
if let metalLayer = scnView.layer as? CAMetalLayer {
metalLayer.framebufferOnly = false
}
第 4 步： 在您的 SCNView 的委托 (SCNSceneRendererDelegate) 中，使用纹理
func renderer(renderer: SCNSceneRenderer, didRenderScene scene: SCNScene, atTime time: NSTimeInterval) {
if let texture = AppManager.sharedInstance.currentSceneDrawable?.texture where !texture.framebufferOnly {
AppManager.sharedInstance.currentSceneDrawable = nil
// Get image from texture
let image = texture.toImage()
// Use the image for video recording
}
}
extension MTLTexture {
func bytes() -> UnsafeMutablePointer<Void> {
let width = self.width
let height = self.height
let rowBytes = self.width * 4
let p = malloc(width * height * 4) //Beware for memory leak
self.getBytes(p, bytesPerRow: rowBytes, fromRegion: MTLRegionMake2D(0, 0, width, height), mipmapLevel: 0)
return p
}
func toImage() -> UIImage? {
var uiImage: UIImage?
let p = bytes()
let pColorSpace = CGColorSpaceCreateDeviceRGB()
let rawBitmapInfo = CGImageAlphaInfo.NoneSkipFirst.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue
let bitmapInfo:CGBitmapInfo = CGBitmapInfo(rawValue: rawBitmapInfo)
let selftureSize = self.width * self.height * 4
let rowBytes = self.width * 4
let provider = CGDataProviderCreateWithData(nil, p, selftureSize, {_,_,_ in })!
if let cgImage = CGImageCreate(self.width, self.height, 8, 32, rowBytes, pColorSpace, bitmapInfo, provider, nil, true, CGColorRenderingIntent.RenderingIntentDefault) {
uiImage = UIImage(CGImage: cgImage)
}
return uiImage
}
func toImageAsJpeg(compressionQuality: CGFloat) -> UIImage? {
}
}
第 5 步（可选）： 您可能需要在 CAMetalLayer 确认您获得的可绘制对象是您的目标。 （如果同时有多个 CAMetalLayer）
【讨论】：
其实很简单！这是我将如何做的伪代码（在 SCNView 上）：
int numberOfFrames = 300;
int currentFrame = 0;
int framesPerSecond = 30;
-(void) renderAFrame{
[self renderAtTime:1/framesPerSecond];
NSImage *frame = [self snapshot];
// save the image with the frame number in the name such as f_001.png
currentFrame++;
if(currentFrame < numberOfFrames){
[self renderAFrame];
}
}
它将以每秒 30 帧的速度为您输出一系列图像，您可以将其导入任何编辑软件并转换为视频。
【讨论】：
您可以使用放入 SKScene 中的 SKVideoNode 来执行此操作，该 SKScene 用于映射为 SCNode 的 SCMaterial.Diffuse.Content（希望这很清楚；））
player = AVPlayer(URL: fileURL!)
let videoSpriteKitNodeLeft = SKVideoNode(AVPlayer: player)
let videoNodeLeft = SCNNode()
let spriteKitScene1 = SKScene(size: CGSize(width: 1280 * screenScale, height: 1280 * screenScale))
spriteKitScene1.shouldRasterize = true
videoNodeLeft.geometry = SCNSphere(radius: 30)
spriteKitScene1.scaleMode = .AspectFit
videoSpriteKitNodeLeft.position = CGPoint(
x: spriteKitScene1.size.width / 2.0, y: spriteKitScene1.size.height / 2.0)
videoSpriteKitNodeLeft.size = spriteKitScene1.size
spriteKitScene1.addChild(videoSpriteKitNodeLeft)
videoNodeLeft.geometry?.firstMaterial?.diffuse.contents = spriteKitScene1
videoNodeLeft.geometry?.firstMaterial?.doubleSided = true
// Flip video upside down, so that it's shown in the right position
var transform = SCNMatrix4MakeRotation(Float(M_PI), 0.0, 0.0, 1.0)
transform = SCNMatrix4Translate(transform, 1.0, 1.0, 0.0)
videoNodeLeft.pivot = SCNMatrix4MakeRotation(Float(M_PI_2), 0.0, -1.0, 0.0)
videoNodeLeft.geometry?.firstMaterial?.diffuse.contentsTransform = transform
videoNodeLeft.position = SCNVector3(x: 0, y: 0, z: 0)
scene.rootNode.addChildNode(videoNodeLeft)
我从我的一个 github 项目中提取了代码，用于使用 SceneKit 在 3D Sphere 中播放视频的 360 视频播放器：https://github.com/Aralekk/simple360player_iOS/blob/master/simple360player/ViewController.swift
我希望这会有所帮助！
亚瑟
【讨论】：