深入探索 Metal 4 游戏

6:46 - Reactive Mask

// Create reactive mask setup in shader
out.reactivity = m_material_id == eRain ? (m_material_id == eSpark ? 1.0f : 0.0f) : 0.8f;

// Set reactive mask before encoding upscaler on host
temporalUpscaler.reactiveMask = reactiveMaskTexture;

8:35 - MetalFX Frame Interpolator

// Create and configure the interpolator descriptor
MTLFXFrameInterpolatorDescriptor* desc = [MTLFXFrameInterpolatorDescriptor new];
desc.scaler = temporalScaler;
// ...

// Create the effect and configure your effect
id<MTLFXFrameInterpolator> interpolator = [desc newFrameInterpolatorWithDevice:device];
interpolator.motionVectorScaleX = mvecScaleX;
interpolator.motionVectorScaleY = mvecScaleY;
interpolator.depthReversed = YES;

// Set input textures
interpolator.colorTexture = colorTexture;
interpolator.prevColorTexture = prevColorTexture;
interpolator.depthTexture = depthTexture;
interpolator.motionTexture = motionTexture;
interpolator.outputTexture = outputTexture;

12:45 - Interpolator present helper class

#include <thread>
#include <mutex>
#include <sys/event.h>
#include <mach/mach_time.h>


class PresentThread
{
    int m_timerQueue;
    std::thread m_encodingThread, m_pacingThread;
    std::mutex m_mutex;
    std::condition_variable m_scheduleCV, m_threadCV, m_pacingCV;
    float m_minDuration;
    
    uint32_t m_width, m_height;
    MTLPixelFormat m_pixelFormat;
    
    const static uint32_t kNumBuffers = 3;
    uint32_t m_bufferIndex, m_inputIndex;
    bool m_renderingUI, m_presentsPending;
    
    CAMetalLayer *m_metalLayer;
    id<MTLCommandQueue> m_presentQueue;

    id<MTLEvent> m_event;
    id<MTLSharedEvent> m_paceEvent, m_paceEvent2;
    uint64_t m_eventValue;
    uint32_t m_paceCount;
    
    int32_t m_numQueued, m_framesInFlight;
    
    id<MTLTexture> m_backBuffers[kNumBuffers];
    id<MTLTexture> m_interpolationOutputs[kNumBuffers];
    id<MTLTexture> m_interpolationInputs[2];
    id<MTLRenderPipelineState> m_copyPipeline;
    
    std::function<void(id<MTLRenderCommandEncoder>)> m_uiCallback = nullptr;
    
    void PresentThreadFunction();
    void PacingThreadFunction();
    
    void CopyTexture(id<MTLCommandBuffer> commandBuffer, id<MTLTexture> dest, id<MTLTexture> src, NSString *label);

public:
    
    PresentThread(float minDuration, CAMetalLayer *metalLayer);
    ~PresentThread()
    {
        std::unique_lock<std::mutex> lock(m_mutex);
        m_numQueued = -1;
        m_threadCV.notify_one();
        m_encodingThread.join();
    }
    void StartFrame(id<MTLCommandBuffer> commandBuffer)
    {
        [commandBuffer encodeWaitForEvent:m_event value:m_eventValue++];
    }

    void StartUI(id<MTLCommandBuffer> commandBuffer)
    {
        assert(m_uiCallback == nullptr);
        if(!m_renderingUI)
        {
            CopyTexture(commandBuffer, m_interpolationInputs[m_inputIndex], m_backBuffers[m_bufferIndex], @"Copy HUDLESS");
            m_renderingUI = true;
        }
    }
    
    void Present(id<MTLFXFrameInterpolator> frameInterpolator, id<MTLCommandQueue> queue);
    
    id<MTLTexture> GetBackBuffer()
    {
        return m_backBuffers[m_bufferIndex];
    }

    void Resize(uint32_t width, uint32_t height, MTLPixelFormat pixelFormat);
    
    void DrainPendingPresents()
    {
        std::unique_lock<std::mutex> lock(m_mutex);
        while(m_presentsPending)
            m_scheduleCV.wait(lock);
    }
    
    bool UICallbackEnabled() const
    {
        return m_uiCallback != nullptr;
    }
    
    void SetUICallback(std::function<void(id<MTLRenderCommandEncoder>)> callback)
    {
        m_uiCallback = callback;
    }
    
};

PresentThread::PresentThread(float minDuration, CAMetalLayer *metalLayer)
    : m_encodingThread(&PresentThread::PresentThreadFunction, this)
    , m_pacingThread(&PresentThread::PacingThreadFunction, this)
    , m_minDuration(minDuration)
    , m_numQueued(0)
    , m_metalLayer(metalLayer)
    , m_inputIndex(0u)
    , m_bufferIndex(0u)
    , m_renderingUI(false)
    , m_presentsPending(false)
    , m_framesInFlight(0)
    , m_paceCount(0)
    , m_eventValue(0)
{
    id<MTLDevice> device = metalLayer.device;
    m_presentQueue = [device newCommandQueue];
    m_presentQueue.label = @"presentQ";
    m_timerQueue = kqueue();
    
    metalLayer.maximumDrawableCount = 3;
    
    Resize(metalLayer.drawableSize.width, metalLayer.drawableSize.height, metalLayer.pixelFormat);
    
    m_event = [device newEvent];
    m_paceEvent = [device newSharedEvent];
	m_paceEvent2 = [device newSharedEvent];
}


void PresentThread::Present(id<MTLFXFrameInterpolator> frameInterpolator, id<MTLCommandQueue> queue)
{
    id<MTLCommandBuffer> commandBuffer = [queue commandBuffer];
    
    if(m_renderingUI)
    {
        frameInterpolator.colorTexture = m_interpolationInputs[m_inputIndex];
        frameInterpolator.prevColorTexture = m_interpolationInputs[m_inputIndex^1];
        frameInterpolator.uiTexture = m_backBuffers[m_bufferIndex];
    }
    else
    {
        frameInterpolator.colorTexture = m_backBuffers[m_bufferIndex];
        frameInterpolator.prevColorTexture = m_backBuffers[(m_bufferIndex + kNumBuffers - 1) % kNumBuffers];
        frameInterpolator.uiTexture = nullptr;
    }
    
    frameInterpolator.outputTexture = m_interpolationOutputs[m_bufferIndex];

    [frameInterpolator encodeToCommandBuffer:commandBuffer];
    [commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> _Nonnull) {
        std::unique_lock<std::mutex> lock(m_mutex);
        m_framesInFlight--;
        m_scheduleCV.notify_one();
        m_paceCount++;
        m_pacingCV.notify_one();
    }];
    [commandBuffer encodeSignalEvent:m_event value:m_eventValue++];
    [commandBuffer commit];

    std::unique_lock<std::mutex> lock(m_mutex);
    m_framesInFlight++;
    m_numQueued++;
    m_presentsPending = true;
    m_threadCV.notify_one();
    while((m_framesInFlight >= 2) || (m_numQueued >= 2))
        m_scheduleCV.wait(lock);

    m_bufferIndex = (m_bufferIndex + 1) % kNumBuffers;
    m_inputIndex = m_inputIndex^1u;
    m_renderingUI = false;
}

void PresentThread::CopyTexture(id<MTLCommandBuffer> commandBuffer, id<MTLTexture> dest, id<MTLTexture> src, NSString *label)
{
    MTLRenderPassDescriptor *desc = [MTLRenderPassDescriptor new];
    desc.colorAttachments[0].texture = dest;
    desc.colorAttachments[0].loadAction = MTLLoadActionDontCare;
    desc.colorAttachments[0].storeAction = MTLStoreActionStore;
    id<MTLRenderCommandEncoder> renderEncoder = [commandBuffer renderCommandEncoderWithDescriptor:desc];
    [renderEncoder setFragmentTexture:src atIndex:0];
    [renderEncoder setRenderPipelineState:m_copyPipeline];
    [renderEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:3];
    if(m_uiCallback)
        m_uiCallback(renderEncoder);
    renderEncoder.label = label;
    [renderEncoder endEncoding];
}


void PresentThread::PacingThreadFunction()
{
    NSThread *thread = [NSThread currentThread];
    [thread setName:@"PacingThread"];
    [thread setQualityOfService:NSQualityOfServiceUserInteractive];
    [thread setThreadPriority:1.f];
    
    mach_timebase_info_data_t info;
    mach_timebase_info(&info);
    
    // maximum delta (0.1ms) in machtime units
    const uint64_t maxDeltaInNanoSecs = 100000000;
    const uint64_t maxDelta = maxDeltaInNanoSecs * info.denom / info.numer;
    
    uint64_t time = mach_absolute_time();
    
    uint64_t paceEventValue = 0;
    
    for(;;)
    {
        std::unique_lock<std::mutex> lock(m_mutex);
        while(m_paceCount == 0)
            m_pacingCV.wait(lock);
        m_paceCount--;
        lock.unlock();
        
        // we get signal...
        const uint64_t prevTime = time;
        time = mach_absolute_time();
		m_paceEvent.signaledValue = ++paceEventValue;

        const uint64_t delta = std::min(time - prevTime, maxDelta);
        const uint64_t timeStamp = time + ((delta*31)>>6);
        
        struct kevent64_s timerEvent, eventOut;
        struct timespec timeout;
        timeout.tv_nsec = maxDeltaInNanoSecs;
        timeout.tv_sec = 0;
        EV_SET64(&timerEvent,
                 0,
                 EVFILT_TIMER,
                 EV_ADD | EV_ONESHOT | EV_ENABLE,
                 NOTE_CRITICAL | NOTE_LEEWAY | NOTE_MACHTIME | NOTE_ABSOLUTE,
                 timeStamp,
                 0,
                 0,
                 0);
        
        kevent64(m_timerQueue, &timerEvent, 1, &eventOut, 1, 0, &timeout);
        
        // main screen turn on...
        m_paceEvent2.signaledValue = ++paceEventValue;
    }
}


void PresentThread::PresentThreadFunction()
{
    NSThread *thread = [NSThread currentThread];
    [thread setName:@"PresentThread"];
    [thread setQualityOfService:NSQualityOfServiceUserInteractive];
    [thread setThreadPriority:1.f];
    

    uint64_t eventValue = 0;
    uint32_t bufferIndex = 0;

    uint64_t paceEventValue = 0;

    for(;;)
    {
        std::unique_lock<std::mutex> lock(m_mutex);
        
        if(m_numQueued == 0)
        {
            m_presentsPending = false;
            m_scheduleCV.notify_one();
        }
        
        while(m_numQueued == 0)
            m_threadCV.wait(lock);
        
        if(m_numQueued < 0)
            break;
        lock.unlock();

        @autoreleasepool
        {
            id<CAMetalDrawable> drawable = [m_metalLayer nextDrawable];

			lock.lock();
			m_numQueued--;
			m_scheduleCV.notify_one();
			lock.unlock();

            id<MTLCommandBuffer> commandBuffer = [m_presentQueue commandBuffer];
            [commandBuffer encodeWaitForEvent:m_event value:++eventValue];
            CopyTexture(commandBuffer, drawable.texture, m_interpolationOutputs[bufferIndex], @"Copy Interpolated");
            [commandBuffer encodeSignalEvent:m_event value:++eventValue];
			[commandBuffer encodeWaitForEvent:m_paceEvent value:++paceEventValue];

            if(m_minDuration > 0.f)
                [commandBuffer presentDrawable:drawable afterMinimumDuration:m_minDuration];
            else
                [commandBuffer presentDrawable:drawable];
            [commandBuffer commit];
        }
        
        @autoreleasepool
        {
            id<MTLCommandBuffer> commandBuffer = [m_presentQueue commandBuffer];
            id<CAMetalDrawable> drawable = [m_metalLayer nextDrawable];
            CopyTexture(commandBuffer, drawable.texture, m_backBuffers[bufferIndex], @"Copy Rendered");
			[commandBuffer encodeWaitForEvent:m_paceEvent2 value:++paceEventValue];
            if(m_minDuration > 0.f)
                [commandBuffer presentDrawable:drawable afterMinimumDuration:m_minDuration];
            else
                [commandBuffer presentDrawable:drawable];
            [commandBuffer commit];
        }
        
        bufferIndex = (bufferIndex + 1) % kNumBuffers;
    }
}

void PresentThread::Resize(uint32_t width, uint32_t height, MTLPixelFormat pixelFormat)
{
    if((m_width != width) || (m_height != height) || (m_pixelFormat != pixelFormat))
    {
        id<MTLDevice> device = m_metalLayer.device;

        if(m_pixelFormat != pixelFormat)
        {
            id<MTLLibrary> lib = [device newDefaultLibrary];
            MTLRenderPipelineDescriptor *pipelineDesc = [MTLRenderPipelineDescriptor new];
            pipelineDesc.vertexFunction = [lib newFunctionWithName:@"FSQ_VS_V4T2"];
            pipelineDesc.fragmentFunction = [lib newFunctionWithName:@"FSQ_simpleCopy"];
            pipelineDesc.colorAttachments[0].pixelFormat = pixelFormat;
            m_copyPipeline = [device newRenderPipelineStateWithDescriptor:pipelineDesc error:nil];
            m_pixelFormat = pixelFormat;
        }
        
        DrainPendingPresents();
        
        m_width = width;
		m_height = height;
        
        MTLTextureDescriptor *texDesc = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:pixelFormat width:width height:height mipmapped:NO];
		texDesc.storageMode = MTLStorageModePrivate;
        for(uint32_t i = 0; i < kNumBuffers; i++)
        {
            texDesc.usage = MTLTextureUsageShaderRead|MTLTextureUsageShaderWrite|MTLTextureUsageRenderTarget;
            m_backBuffers[i] = [device newTextureWithDescriptor:texDesc];
            texDesc.usage = MTLTextureUsageShaderRead|MTLTextureUsageRenderTarget;
            m_interpolationOutputs[i] = [device newTextureWithDescriptor:texDesc];
        }
        texDesc.usage = MTLTextureUsageShaderRead|MTLTextureUsageRenderTarget;
        m_interpolationInputs[0] = [device newTextureWithDescriptor:texDesc];
        m_interpolationInputs[1] = [device newTextureWithDescriptor:texDesc];

    }
}

13:00 - Set intersection function table offset

// Set intersection function table offset on host-side geometry descriptors
NSMutableArray<MTLAccelerationStructureGeometryDescriptor *> *geomDescs ...;
for (auto g = 0; g < geomList.size(); ++g)
{
    MTLAccelerationStructureGeometryDescriptor *descriptor = ...;
    descriptor.intersectionFunctionTableOffset = g;
    ...
    [geomDescs addObject:descriptor];
}

13:01 - Set up the intersector

// Set up the intersector
metal::raytracing::intersector<intersection_function_buffer, instancing, triangle> trace;
trace.set_geometry_multiplier(2); // Number of ray types, defaults to 1
trace.set_base_id(1);             // Set ray type index, defaults to 0

13:02 - Ray trace intersection function buffers

// Ray trace intersection function buffers

// Set up intersection function buffer arguments
intersection_function_buffer_arguments ifb_arguments;
ifb_arguments.intersection_function_buffer = raytracingResources.ifbBuffer;
ifb_arguments.intersection_function_buffer_size = raytracingResources.ifbBufferSize;
ifb_arguments.intersection_function_stride = raytracingResources.ifbBufferStride;

// Set up the ray and finish intersecting
metal::raytracing::ray r = { origin, direction };
auto result = trace.intersect(r, ads, ifb_arguments);

13:02 - Change of temporal scaler setup to denoised temporal scaler setup

// Change of temporal scaler setup to denoised temporal scaler setup

MTLFXTemporalScalerDescriptor* desc = [MTLFXTemporalScalerDescriptor new];
desc.colorTextureFormat = MTLPixelFormatBGRA8Unorm_sRGB;
desc.outputTextureFormat = MTLPixelFormatBGRA8Unorm_sRGB;
desc.depthTextureFormat = DepthStencilFormat;
desc.motionTextureFormat = MotionVectorFormat;

desc.diffuseAlbedoTextureFormat = DiffuseAlbedoFormat;
desc.specularAlbedoTextureFormat = SpecularAlbedoFormat;
desc.normalTextureFormat = NormalVectorFormat;
desc.roughnessTextureFormat = RoughnessFormat;

desc.inputWidth = _mainViewWidth;
desc.inputHeight = _mainViewHeight;
desc.outputWidth = _screenWidth;
desc.outputHeight = _screenHeight;
temporalScaler = [desc newTemporalDenoisedScalerWithDevice:_device];

13:04 - Change temporal scaler encode to denoiser temporal scaler encode

// Change temporal scaler encode to denoiser temporal scaler encode

temporalScaler.colorTexture = _mainView;
temporalScaler.motionTexture = _motionTexture;

temporalScaler.diffuseAlbedoTexture = _diffuseAlbedoTexture;
temporalScaler.specularAlbedoTexture = _specularAlbedoTexture;
temporalScaler.normalTexture = _normalTexture;
temporalScaler.roughnessTexture = _roughnessTexture;

temporalScaler.depthTexture = _depthTexture;
temporalScaler.jitterOffsetX = _pixelJitter.x;
temporalScaler.jitterOffsetY = -_pixelJitter.y;
temporalScaler.outputTexture = _upscaledColorTarget;
temporalScaler.motionVectorScaleX = (float)_motionTexture.width;
temporalScaler.motionVectorScaleY = (float)_motionTexture.height;
[temporalScaler encodeToCommandBuffer:commandBuffer];

16:04 - Creating instance descriptors for instance acceleration structure

// Creating instance descriptors for instance acceleration structure
MTLAccelerationStructureInstanceDescriptor *grassInstanceDesc, *treeInstanceDesc = . . .;
grassInstanceDesc.intersectionFunctionTableOffset = 0;
treeInstanceDesc.intersectionFunctionTableOffset  = 1;

// Create buffer for instance descriptors of as many trees/grass instances the scene holds
id <MTLBuffer> instanceDescs = . . .;
for (auto i = 0; i < scene.instances.size(); ++i)
. . .