FSRPackage/Runtime/OpticalFlow/OpticalFlow.cs

using System;
using System.Runtime.InteropServices;
using UnityEngine;

namespace FidelityFX.OpticalFlow
{
    public static class OpticalFlow
    {
        internal const int OpticalFlowMaxPyramidLevels = 7;
        internal const int HistogramBins = 256;
        internal const int HistogramsPerDim = 3;
        internal const int HistogramShifts = 3;
        
        public static OpticalFlowContext CreateContext(in ContextDescription contextDescription)
        {
            throw new NotImplementedException();
        }
        
        public struct ContextDescription
        {
            public Vector2Int resolution;
            public OpticalFlowShaders shaders;
        }

        public struct DispatchDescription
        {
            public ResourceView color;
            public ResourceView opticalFlowVector;
            public ResourceView opticalFlowSCD;
            public bool reset;
            public int backbufferTransferFunction;
            public Vector2 minMaxLuminance;
        }
        
        internal static Vector2Int GetOpticalFlowTextureSize(Vector2Int displaySize, int opticalFlowBlockSize)
        {
            int width = (displaySize.x + opticalFlowBlockSize - 1) / opticalFlowBlockSize;
            int height = (displaySize.y + opticalFlowBlockSize - 1) / opticalFlowBlockSize;
            return new Vector2Int(width, height);
        }

        internal static Vector2Int GetOpticalFlowHistogramSize(int level)
        {
            const int searchRadius = 8;
            int maxVelocity = searchRadius * (1 << (OpticalFlowMaxPyramidLevels - 1 - level));
            int binsPerDimension = 2 * maxVelocity + 1;
            return new Vector2Int(binsPerDimension, binsPerDimension);
        }

        internal static Vector2Int GetGlobalMotionSearchDispatchSize(int level)
        {
            const int threadGroupSizeX = 16;
            const int threadGroupSizeY = 16;
            Vector2Int opticalFlowHistogramSize = GetOpticalFlowHistogramSize(level);
            int additionalElementsDueToShiftsX = opticalFlowHistogramSize.x / threadGroupSizeX;
            int additionalElementsDueToShiftsY = opticalFlowHistogramSize.y / threadGroupSizeY;
            int dispatchX = (opticalFlowHistogramSize.x + additionalElementsDueToShiftsX + threadGroupSizeX - 1) / threadGroupSizeX;
            int dispatchY = (opticalFlowHistogramSize.y + additionalElementsDueToShiftsY + threadGroupSizeY - 1) / threadGroupSizeY;
            return new Vector2Int(dispatchX, dispatchY);
        }

        internal static int GetSCDHistogramTextureWidth()
        {
            return HistogramBins * (HistogramsPerDim * HistogramsPerDim);
        }
        
        [Serializable, StructLayout(LayoutKind.Sequential)]
        internal struct OpticalFlowConstants
        {
            public Vector2Int inputLumaResolution;
            public uint opticalFlowPyramidLevel;
            public uint opticalFlowPyramidLevelCount;

            public int frameIndex;
            public uint backbufferTransferFunction;
            public Vector2 minMaxLuminance;
        }
        
        [Serializable, StructLayout(LayoutKind.Sequential)]
        internal struct SpdConstants
        {
            public uint mips;
            public uint numWorkGroups;
            public uint workGroupOffsetX;
            public uint workGroupOffsetY;

            public uint numWorkGroupsOpticalFlowInputPyramid;
            public uint pad0_;
            public uint pad1_;
            public uint pad2_;
        }
    }
}