我正在创建一个简单的纹理显示，它实质上通过金属显示呈现BGRA格式的视频帧。我遵循Metal WWDC会话中讲述的相同步骤。但是我在创建渲染编码器时遇到了问题。我的代码是
id <MTLDevice> device = MTLCreateSystemDefaultDevice();
id<MTLCommandQueue> commandQueue = [device newCommandQueue];
id<MTLLibrary> library = [device newDefaultLibrary];
// Create Render Command Descriptor.
MTLRenderPipelineDescriptor* renderPipelineDesc = [MTLRenderPipelineDescriptor new];
renderPipelineDesc.colorAttachments[0].pixelFormat = MTLPixelFormatBGRA8Unorm;
renderPipelineDesc.vertexFunction = [library newFunctionWithName:@"basic_vertex"];
renderPipelineDesc.fragmentFunction = [library newFunctionWithName:@"basic_fragment"];
NSError* error = nil;
id<MTLRenderPipelineState> renderPipelineState = [device newRenderPipelineStateWithDescriptor:renderPipelineDesc
error:&error];
id<MTLCommandBuffer> commandBuffer = [commandQueue commandBuffer];
MTLRenderPassDescriptor* renderPassDesc = [MTLRenderPassDescriptor renderPassDescriptor];
id<CAMetalDrawable> drawable = [_metalLayer nextDrawable];
MTLRenderPassColorAttachmentDescriptor* colorAttachmentDesc = [MTLRenderPassColorAttachmentDescriptor new];
colorAttachmentDesc.texture = drawable.texture;
colorAttachmentDesc.loadAction = MTLLoadActionLoad;
colorAttachmentDesc.storeAction = MTLStoreActionStore;
colorAttachmentDesc.clearColor = MTLClearColorMake(0, 0, 0, 1);
[renderPassDesc.colorAttachments setObject:colorAttachmentDesc atIndexedSubscript:0];
[inTexture replaceRegion:region
mipmapLevel:0
withBytes:imageBytes
bytesPerRow:CVPixelBufferGetBytesPerRow(_image)];
id<MTLRenderCommandEncoder> renderCmdEncoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDesc];
[renderCmdEncoder setRenderPipelineState:_renderPipelineState];
[renderCmdEncoder endEncoding];
这段代码崩溃，说'＆34;找不到渲染目标＆＃34; id renderCmdEncoder = [commandBuffer renderCommandEncoderWithDescriptor：renderPassDesc]; 我无法确定在何处以及如何设置渲染目标。
答案 0 :(得分：0)
这将完美地运作;如果您需要帮助实现它，请告诉我：
@import UIKit;
@import AVFoundation;
@import CoreMedia;
#import <MetalKit/MetalKit.h>
#import <Metal/Metal.h>
#import <MetalPerformanceShaders/MetalPerformanceShaders.h>
@interface ViewController : UIViewController <MTKViewDelegate, AVCaptureVideoDataOutputSampleBufferDelegate> {
NSString *_displayName;
NSString *serviceType;
}
@property (retain, nonatomic) SessionContainer *session;
@property (retain, nonatomic) AVCaptureSession *avSession;
@end;
#import "ViewController.h"
@interface ViewController () {
MTKView *_metalView;
id<MTLDevice> _device;
id<MTLCommandQueue> _commandQueue;
id<MTLTexture> _texture;
CVMetalTextureCacheRef _textureCache;
}
@property (strong, nonatomic) AVCaptureDevice *videoDevice;
@property (nonatomic) dispatch_queue_t sessionQueue;
@end
@implementation ViewController
- (void)viewDidLoad {
NSLog(@"%s", __PRETTY_FUNCTION__);
[super viewDidLoad];
_device = MTLCreateSystemDefaultDevice();
_metalView = [[MTKView alloc] initWithFrame:self.view.bounds];
[_metalView setContentMode:UIViewContentModeScaleAspectFit];
_metalView.device = _device;
_metalView.delegate = self;
_metalView.clearColor = MTLClearColorMake(1, 1, 1, 1);
_metalView.colorPixelFormat = MTLPixelFormatBGRA8Unorm;
_metalView.framebufferOnly = NO;
_metalView.autoResizeDrawable = NO;
CVMetalTextureCacheCreate(NULL, NULL, _device, NULL, &_textureCache);
[self.view addSubview:_metalView];
self.sessionQueue = dispatch_queue_create( "session queue", DISPATCH_QUEUE_SERIAL );
if ([self setupCamera]) {
[_avSession startRunning];
}
}
- (BOOL)setupCamera {
NSLog(@"%s", __PRETTY_FUNCTION__);
@try {
NSError * error;
_avSession = [[AVCaptureSession alloc] init];
[_avSession beginConfiguration];
[_avSession setSessionPreset:AVCaptureSessionPreset640x480];
// get list of devices; connect to front-facing camera
self.videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
if (self.videoDevice == nil) return FALSE;
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:self.videoDevice error:&error];
[_avSession addInput:input];
dispatch_queue_t sampleBufferQueue = dispatch_queue_create("CameraMulticaster", DISPATCH_QUEUE_SERIAL);
AVCaptureVideoDataOutput * dataOutput = [[AVCaptureVideoDataOutput alloc] init];
[dataOutput setAlwaysDiscardsLateVideoFrames:YES];
[dataOutput setVideoSettings:@{(id)kCVPixelBufferPixelFormatTypeKey: @(kCVPixelFormatType_32BGRA)}];
[dataOutput setSampleBufferDelegate:self queue:sampleBufferQueue];
[_avSession addOutput:dataOutput];
[_avSession commitConfiguration];
} @catch (NSException *exception) {
NSLog(@"%s - %@", __PRETTY_FUNCTION__, exception.description);
return FALSE;
} @finally {
return TRUE;
}
}
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
{
size_t width = CVPixelBufferGetWidth(pixelBuffer);
size_t height = CVPixelBufferGetHeight(pixelBuffer);
CVMetalTextureRef texture = NULL;
CVReturn status = CVMetalTextureCacheCreateTextureFromImage(kCFAllocatorDefault, _textureCache, pixelBuffer, NULL, MTLPixelFormatBGRA8Unorm, width, height, 0, &texture);
if(status == kCVReturnSuccess)
{
_metalView.drawableSize = CGSizeMake(width, height);
_texture = CVMetalTextureGetTexture(texture);
_commandQueue = [_device newCommandQueue];
CFRelease(texture);
}
}
}
- (void)drawInMTKView:(MTKView *)view {
// creating command encoder
if (_texture) {
id<MTLCommandBuffer> commandBuffer = [_commandQueue commandBuffer];
id<MTLTexture> drawingTexture = view.currentDrawable.texture;
// set up and encode the filter
MPSImageGaussianBlur *filter = [[MPSImageGaussianBlur alloc] initWithDevice:_device sigma:5];
[filter encodeToCommandBuffer:commandBuffer sourceTexture:_texture destinationTexture:drawingTexture];
// committing the drawing
[commandBuffer presentDrawable:view.currentDrawable];
[commandBuffer commit];
_texture = nil;
}
}
- (void)mtkView:(MTKView *)view drawableSizeWillChange:(CGSize)size {
}
@end
答案 1 :(得分：0)
你应该尝试以下几点之一
1.不使用创建新的渲染过程描述符，而是使用来自MTKView对象的当前渲染过程描述符对象。这个渲染过程描述符已经被配置。你不需要设置任何东西。下面给出的示例代码 -
renderPassDescriptor.colorAttachments[0].clearColor =
MTLClearColor(red:
0.0,green: 0.0,blue: 0.0,alpha: 1.0)
renderPassDescriptor.colorAttachments[0].loadAction = .clear
renderPassDescriptor.colorAttachments[0].storeAction = .store
renderPassDescriptor.depthAttachment.clearDepth = 1.0
renderPassDescriptor.depthAttachment.loadAction = .clear
renderPassDescriptor.depthAttachment.storeAction = .dontCare
let view = self.view as!MTKView
let textDesc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat:
.bgra8Unorm, width: Int(view.frame.width),
height: Int(view.frame.height), mipmapped: false)
textDesc.depth = 1
//see below line
textDesc.usage =
[MTLTextureUsage.renderTarget,MTLTextureUsage.shaderRead]
textDesc.storageMode = .private
mainPassFrameBuffer = device.makeTexture(descriptor: textDesc)
renderPassDescriptor.colorAttachments[0].texture = mainPassFrameBuffer
2.您正在创建一个新的渲染过程描述符，然后通过可绘制对象的纹理设置其颜色附件，因此您应该创建一个新的纹理对象，然后将此纹理的用法设置为渲染目标。然后将获得在新纹理中呈现的内容，但它不会显示在屏幕上，因此要显示您的textue内容，您必须在可绘制纹理中复制纹理内容，然后呈现可绘制。
下面是制作渲染目标的代码 -
public void askLocation() {
if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
Criteria criteria = new Criteria();
String provider = locationManager.getBestProvider(criteria, true);
try {
mLocation = locationManager.getLastKnownLocation(provider);
} catch (SecurityException e) {
//
}
String currentCoordinates = somename.getString("LastLocation", "0,0");
if (mLocation != null) {
double currentLatitude = mLocation.getLatitude();
double currentLongitude = mLocation.getLongitude();
currentCoordinates = currentLatitude + "," + currentLongitude;
}
SharedPreferences.Editor editor = somename.edit();
editor.putString("LastLocation", currentCoordinates).commit();
Log.d("SomeName", "lastLocation start: " + currentCoordinates);
}
}