Add Custom Frame Modification Hook API for Video Rendering

API/FrameHookContext.cs

@@ -0,0 +1,302 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using UnityEngine;
+using UnityEngine.Rendering;
+
+namespace ADOFAIRenderer.API;
+
+/// <summary>
+/// Execution context provided to frame modification hooks, managing GPU ping-pong double buffering.
+/// </summary>
+/// <remarks>
+/// <para>
+/// <b>Zero-Allocation Notice:</b> For maximum performance on the render hot path, the pipeline reuses context instances
+/// across frames. Do not cache the context instance itself across frames.
+/// </para>
+/// <para>
+/// <b>Execution Frequency Notice:</b> This hook is executed only when a frame is captured for video encoding.
+/// When <c>RenderFPS</c> exceeds <c>VideoFPS</c>, intermediate game rendering frames are skipped and the hook
+/// will <b>not</b> be invoked on every rendered game frame.
+/// </para>
+/// </remarks>
+[SuppressMessage("ReSharper", "UnusedType.Global")]
+[SuppressMessage("ReSharper", "UnusedMember.Global")]
+[SuppressMessage("ReSharper", "MemberCanBePrivate.Global")]
+[SuppressMessage("ReSharper", "UnusedAutoPropertyAccessor.Global")]
+public class FrameHookContext
+{
+    private RenderTexture _originalSource = null!;
+    private RenderTexture _pingRT = null!;
+    private RenderTexture _pongRT = null!;
+
+    private RenderTexture _currentSource = null!;
+    private RenderTexture _currentDestination = null!;
+    private bool _hasModified;
+
+    /// <summary>
+    /// The input <see cref="RenderTexture"/> containing the rendered frame before the current pass.
+    /// </summary>
+    public RenderTexture Source => _currentSource;
+
+    /// <summary>
+    /// The writable destination <see cref="RenderTexture"/> for the current pass.
+    /// </summary>
+    public RenderTexture Destination => _currentDestination;
+
+    /// <summary>
+    /// The active <see cref="RenderTexture"/> representing the current state of the modified frame.
+    /// </summary>
+    public RenderTexture Current => _currentSource;
+
+    /// <summary>
+    /// The original unmodified render texture captured from the game for the current frame before any hooks were applied.
+    /// </summary>
+    public RenderTexture OriginalSource => _originalSource;
+
+    /// <summary>
+    /// Indicates whether any modifications or swaps have been applied to this frame.
+    /// </summary>
+    public bool HasModified => _hasModified;
+
+    /// <summary>
+    /// The sequential 0-based index of the video frame currently being encoded.
+    /// </summary>
+    public long FrameIndex { get; private set; }
+
+    /// <summary>
+    /// Alias for <see cref="FrameIndex"/>. The sequential 0-based index of the video frame.
+    /// </summary>
+    public long VideoFrameIndex => FrameIndex;
+
+    /// <summary>
+    /// The sequential 0-based index of the game render frame.
+    /// </summary>
+    public long RenderFrameIndex { get; private set; }
+
+    /// <summary>
+    /// The timestamp of the current frame in seconds relative to video start.
+    /// </summary>
+    public double VideoTime { get; private set; }
+
+    /// <summary>
+    /// The delta time duration in seconds of a single video frame (equivalent to 1.0 / VideoFPS).
+    /// </summary>
+    public double DeltaTime => VideoFPS > 0 ? 1.0 / VideoFPS : 0.0;
+
+    /// <summary>
+    /// The width of the frame in pixels.
+    /// </summary>
+    public int Width => _currentSource.width;
+
+    /// <summary>
+    /// The height of the frame in pixels.
+    /// </summary>
+    public int Height => _currentSource.height;
+
+    /// <summary>
+    /// The configured render frames per second.
+    /// </summary>
+    public double RenderFPS { get; private set; }
+
+    /// <summary>
+    /// The output video frames per second.
+    /// </summary>
+    public double VideoFPS { get; private set; }
+
+    /// <summary>
+    /// The number of successful modification passes completed for the current frame.
+    /// </summary>
+    public int PassCount { get; private set; }
+
+    internal FrameHookContext(
+        RenderTexture originalSource,
+        RenderTexture pingRT,
+        RenderTexture pongRT,
+        RenderTexture firstDestination,
+        long frameIndex,
+        long renderFrameIndex,
+        double videoTime,
+        double renderFps,
+        double videoFps)
+    {
+        Reset(originalSource, pingRT, pongRT, firstDestination, frameIndex, renderFrameIndex, videoTime, renderFps, videoFps);
+    }
+
+    internal void Reset(
+        RenderTexture originalSource,
+        RenderTexture pingRT,
+        RenderTexture pongRT,
+        RenderTexture firstDestination,
+        long frameIndex,
+        long renderFrameIndex,
+        double videoTime,
+        double renderFps,
+        double videoFps)
+    {
+        _originalSource = originalSource;
+        _pingRT = pingRT;
+        _pongRT = pongRT;
+
+        _currentSource = originalSource;
+        _currentDestination = firstDestination;
+        _hasModified = false;
+        PassCount = 0;
+
+        FrameIndex = frameIndex;
+        RenderFrameIndex = renderFrameIndex;
+        VideoTime = videoTime;
+        RenderFPS = renderFps;
+        VideoFPS = videoFps;
+    }
+
+    /// <summary>
+    /// Blits from <see cref="Source"/> to <see cref="Destination"/> using the specified <see cref="Material"/> and automatically swaps ping-pong buffers.
+    /// </summary>
+    /// <param name="material">The material containing the shader to apply, or <c>null</c> for a standard copy.</param>
+    /// <param name="pass">The shader pass index to use, or -1 to execute all passes.</param>
+    public void Blit(Material? material = null, int pass = -1)
+    {
+        if (material != null)
+        {
+            if (pass >= 0)
+                Graphics.Blit(_currentSource, _currentDestination, material, pass);
+            else
+                Graphics.Blit(_currentSource, _currentDestination, material);
+        }
+        else
+        {
+            Graphics.Blit(_currentSource, _currentDestination);
+        }
+
+        Swap();
+    }
+
+    /// <summary>
+    /// Blits from a custom source <see cref="Texture"/> to <see cref="Destination"/> using the specified <see cref="Material"/> and automatically swaps ping-pong buffers.
+    /// </summary>
+    /// <param name="customSource">The custom source texture to blit from.</param>
+    /// <param name="material">The material containing the shader to apply, or <c>null</c> for a standard copy.</param>
+    /// <param name="pass">The shader pass index to use, or -1 to execute all passes.</param>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="customSource"/> is null.</exception>
+    public void Blit(Texture customSource, Material? material = null, int pass = -1)
+    {
+        if (customSource == null) throw new ArgumentNullException(nameof(customSource));
+
+        if (material != null)
+        {
+            if (pass >= 0)
+                Graphics.Blit(customSource, _currentDestination, material, pass);
+            else
+                Graphics.Blit(customSource, _currentDestination, material);
+        }
+        else
+        {
+            Graphics.Blit(customSource, _currentDestination);
+        }
+
+        Swap();
+    }
+
+    /// <summary>
+    /// Copies the contents of <see cref="Source"/> into <see cref="Destination"/> without swapping buffers.
+    /// Call this before drawing custom overlays into <see cref="Destination"/> if you wish to preserve the background.
+    /// </summary>
+    public void Copy()
+    {
+        Graphics.Blit(_currentSource, _currentDestination);
+    }
+
+    /// <summary>
+    /// Clears <see cref="Destination"/> with the specified color.
+    /// </summary>
+    /// <param name="clearColor">The color to clear with, or <c>null</c> for <see cref="Color.clear"/>.</param>
+    public void ClearDestination(Color? clearColor = null)
+    {
+        var prev = RenderTexture.active;
+        try
+        {
+            RenderTexture.active = _currentDestination;
+            GL.Clear(false, true, clearColor ?? Color.clear);
+        }
+        finally
+        {
+            RenderTexture.active = prev;
+        }
+    }
+
+    /// <summary>
+    /// Temporarily activates <see cref="Destination"/> as <see cref="RenderTexture.active"/> to perform custom draw calls,
+    /// safely restoring the previous active RenderTexture afterwards.
+    /// </summary>
+    /// <param name="drawAction">The action that performs custom draw operations.</param>
+    /// <param name="autoSwap">If <c>true</c> (default), automatically calls <see cref="Swap"/> after drawing.</param>
+    /// <param name="preserveBackground">If <c>true</c>, copies <see cref="Source"/> into <see cref="Destination"/> before executing <paramref name="drawAction"/>.</param>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="drawAction"/> is null.</exception>
+    public void DrawToDestination(Action drawAction, bool autoSwap = true, bool preserveBackground = false)
+    {
+        if (drawAction == null) throw new ArgumentNullException(nameof(drawAction));
+
+        if (preserveBackground)
+        {
+            Copy();
+        }
+
+        var prev = RenderTexture.active;
+        try
+        {
+            RenderTexture.active = _currentDestination;
+            drawAction();
+        }
+        finally
+        {
+            RenderTexture.active = prev;
+        }
+
+        if (autoSwap)
+        {
+            Swap();
+        }
+    }
+
+    /// <summary>
+    /// Executes a <see cref="CommandBuffer"/> against the GPU and optionally swaps buffers.
+    /// </summary>
+    /// <param name="commandBuffer">The command buffer to execute.</param>
+    /// <param name="autoSwap">If <c>true</c> (default), automatically calls <see cref="Swap"/> after execution.</param>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="commandBuffer"/> is null.</exception>
+    public void ExecuteCommandBuffer(CommandBuffer commandBuffer, bool autoSwap = true)
+    {
+        if (commandBuffer == null) throw new ArgumentNullException(nameof(commandBuffer));
+        Graphics.ExecuteCommandBuffer(commandBuffer);
+        if (autoSwap)
+        {
+            Swap();
+        }
+    }
+
+    /// <summary>
+    /// Swaps the active <see cref="Source"/> and <see cref="Destination"/> ping-pong buffers.
+    /// Call this after manually writing or rendering into <see cref="Destination"/> so that subsequent hooks or the video encoder read the updated frame.
+    /// </summary>
+    public void Swap()
+    {
+        _hasModified = true;
+        PassCount++;
+
+        var previousDestination = _currentDestination;
+        _currentSource = previousDestination;
+        _currentDestination = (previousDestination == _pingRT) ? _pongRT : _pingRT;
+    }
+
+    /// <summary>
+    /// Replaces the current modified frame texture with a custom <see cref="RenderTexture"/>.
+    /// </summary>
+    /// <param name="customTexture">The custom texture to set as the active frame.</param>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="customTexture"/> is null.</exception>
+    public void ReplaceCurrent(RenderTexture customTexture)
+    {
+        _currentSource = customTexture ?? throw new ArgumentNullException(nameof(customTexture));
+        _hasModified = true;
+        PassCount++;
+    }
+}

API/IFrameHook.cs

@@ -0,0 +1,24 @@
+using System.Diagnostics.CodeAnalysis;
+
+namespace ADOFAIRenderer.API;
+
+/// <summary>
+/// Represents a custom frame modification hook that can modify rendered frames using GPU ping-pong double buffering.
+/// </summary>
+/// <remarks>
+/// <b>Execution Frequency Note:</b> Frame hooks are only invoked for frames that are actually encoded into the final video (<c>VideoFPS</c>).
+/// When <c>RenderFPS</c> is higher than <c>VideoFPS</c>, intermediate game render frames are skipped and this hook
+/// will <b>not</b> be called on every game frame.
+/// </remarks>
+[SuppressMessage("ReSharper", "UnusedType.Global")]
+public interface IFrameHook
+{
+    /// <summary>
+    /// Invoked for each captured video frame before it is encoded.
+    /// </summary>
+    /// <remarks>
+    /// This method is not called on every rendered game frame if <c>RenderFPS</c> exceeds <c>VideoFPS</c>.
+    /// </remarks>
+    /// <param name="context">The frame hook context providing access to ping-pong textures and frame metadata.</param>
+    void OnRenderFrame(FrameHookContext context);
+}

API/RenderSession.cs

@@ -1,9 +1,11 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using ADOFAIRenderer.Core;
 using ADOFAIRenderer.Data;
 using ADOFAIRenderer.Util;
+using UnityEngine;
 
 namespace ADOFAIRenderer.API;
 
@@ -11,8 +13,47 @@ namespace ADOFAIRenderer.API;
 /// Fluent builder for configuring and starting a render session.
 /// </summary>
 [SuppressMessage("ReSharper", "UnusedType.Global")]
+[SuppressMessage("ReSharper", "UnusedMember.Global")]
+[SuppressMessage("ReSharper", "MemberCanBePrivate.Global")]
 public class RenderSession
 {
+    private sealed class GlobalHookRegistration : IDisposable
+    {
+        public object Key { get; }
+        public Action<FrameHookContext> Action { get; }
+        private bool _isDisposed;
+
+        public GlobalHookRegistration(object key, Action<FrameHookContext> action)
+        {
+            Key = key;
+            Action = action;
+        }
+
+        public void Dispose()
+        {
+            if (_isDisposed) return;
+            _isDisposed = true;
+            RemoveGlobalRegistration(this);
+        }
+    }
+
+    private sealed class SessionHookEntry
+    {
+        public object Key { get; }
+        public Action<FrameHookContext> Action { get; }
+
+        public SessionHookEntry(object key, Action<FrameHookContext> action)
+        {
+            Key = key;
+            Action = action;
+        }
+    }
+
+    private static readonly List<GlobalHookRegistration> GlobalFrameHooks = new();
+    private static readonly object GlobalHooksLock = new();
+    private static int _globalHooksVersion;
+
+    private readonly List<SessionHookEntry> _frameHooks = new();
     private bool _auto = true;
 
     /// <summary>
@@ -126,6 +167,331 @@ public class RenderSession
         return this;
     }
 
+    /// <summary>
+    /// Adds a custom frame modification hook to be executed for each encoded video frame.
+    /// The hook can modify the rendered frame using GPU ping-pong double buffering.
+    /// </summary>
+    /// <remarks>
+    /// <b>Execution Frequency Note:</b> This hook is invoked only for frames that are captured for the output video.
+    /// When <c>RenderFPS</c> is higher than <c>VideoFPS</c>, intermediate game render frames are skipped,
+    /// so this hook will <b>not</b> be called on every game frame.
+    /// </remarks>
+    /// <param name="hook">The callback action that receives a <see cref="FrameHookContext"/>.</param>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="hook"/> is null.</exception>
+    public RenderSession AddFrameHook(Action<FrameHookContext> hook)
+    {
+        if (hook == null) throw new ArgumentNullException(nameof(hook));
+        _frameHooks.Add(new SessionHookEntry(hook, hook));
+        return this;
+    }
+
+    /// <summary>
+    /// Adds a material-based post-processing pass to be executed for each encoded video frame.
+    /// Automatically performs a GPU blit from source to destination and swaps buffers.
+    /// </summary>
+    /// <param name="material">The material containing the shader to apply.</param>
+    /// <param name="pass">The shader pass index to use, or -1 to execute all passes.</param>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="material"/> is null.</exception>
+    public RenderSession AddFrameHook(Material material, int pass = -1)
+    {
+        if (material is null) throw new ArgumentNullException(nameof(material));
+        _frameHooks.Add(new SessionHookEntry(material, context => context.Blit(material, pass)));
+        return this;
+    }
+
+    /// <summary>
+    /// Adds a custom frame modification hook implementing <see cref="IFrameHook"/>.
+    /// </summary>
+    /// <param name="hook">The hook instance to execute.</param>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="hook"/> is null.</exception>
+    public RenderSession AddFrameHook(IFrameHook hook)
+    {
+        if (hook == null) throw new ArgumentNullException(nameof(hook));
+        _frameHooks.Add(new SessionHookEntry(hook, hook.OnRenderFrame));
+        return this;
+    }
+
+    /// <summary>
+    /// Alias for <see cref="AddFrameHook(Action{FrameHookContext})"/>.
+    /// </summary>
+    /// <param name="hook">The callback action that receives a <see cref="FrameHookContext"/>.</param>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    public RenderSession WithFrameHook(Action<FrameHookContext> hook) => AddFrameHook(hook);
+
+    /// <summary>
+    /// Alias for <see cref="AddFrameHook(Material, int)"/>.
+    /// </summary>
+    /// <param name="material">The material containing the shader to apply.</param>
+    /// <param name="pass">The shader pass index to use, or -1 to execute all passes.</param>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    public RenderSession WithFrameHook(Material material, int pass = -1) => AddFrameHook(material, pass);
+
+    /// <summary>
+    /// Alias for <see cref="AddFrameHook(IFrameHook)"/>.
+    /// </summary>
+    /// <param name="hook">The hook instance to execute.</param>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    public RenderSession WithFrameHook(IFrameHook hook) => AddFrameHook(hook);
+
+    /// <summary>
+    /// Removes a previously added frame modification hook callback from this session.
+    /// </summary>
+    /// <param name="hook">The hook action to remove.</param>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    public RenderSession RemoveFrameHook(Action<FrameHookContext> hook)
+    {
+        var idx = _frameHooks.FindIndex(e => ReferenceEquals(e.Key, hook) || Equals(e.Action, hook));
+        if (idx >= 0) _frameHooks.RemoveAt(idx);
+        return this;
+    }
+
+    /// <summary>
+    /// Removes a previously added material-based post-processing pass from this session.
+    /// </summary>
+    /// <param name="material">The material to remove.</param>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    public RenderSession RemoveFrameHook(Material material)
+    {
+        if (material)
+        {
+            for (var i = _frameHooks.Count - 1; i >= 0; i--)
+            {
+                if (ReferenceEquals(_frameHooks[i].Key, material))
+                {
+                    _frameHooks.RemoveAt(i);
+                }
+            }
+        }
+        return this;
+    }
+
+    /// <summary>
+    /// Removes a previously added <see cref="IFrameHook"/> from this session.
+    /// </summary>
+    /// <param name="hook">The hook instance to remove.</param>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    public RenderSession RemoveFrameHook(IFrameHook hook)
+    {
+        var idx = _frameHooks.FindIndex(e => ReferenceEquals(e.Key, hook));
+        if (idx >= 0) _frameHooks.RemoveAt(idx);
+        return this;
+    }
+
+    /// <summary>
+    /// Clears all frame modification hooks configured for this render session.
+    /// </summary>
+    /// <returns>The current <see cref="RenderSession"/> instance for method chaining.</returns>
+    public RenderSession ClearFrameHooks()
+    {
+        _frameHooks.Clear();
+        return this;
+    }
+
+    /// <summary>
+    /// Registers a global frame modification hook that will execute on every render session.
+    /// </summary>
+    /// <remarks>
+    /// <b>Execution Frequency Note:</b> Global frame hooks are executed only for frames that are captured for the output video.
+    /// When <c>RenderFPS</c> is higher than <c>VideoFPS</c>, intermediate game render frames are skipped,
+    /// so this hook will <b>not</b> be called on every game frame.
+    /// </remarks>
+    /// <param name="hook">The callback action that receives a <see cref="FrameHookContext"/>.</param>
+    /// <returns>An <see cref="IDisposable"/> registration handle that unregisters the hook when disposed.</returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="hook"/> is null.</exception>
+    public static IDisposable AddGlobalFrameHook(Action<FrameHookContext> hook)
+    {
+        if (hook == null) throw new ArgumentNullException(nameof(hook));
+        var reg = new GlobalHookRegistration(hook, hook);
+        lock (GlobalHooksLock)
+        {
+            GlobalFrameHooks.Add(reg);
+            _globalHooksVersion++;
+        }
+        return reg;
+    }
+
+    /// <summary>
+    /// Registers a global material-based post-processing pass that will execute on every render session.
+    /// </summary>
+    /// <param name="material">The material containing the shader to apply.</param>
+    /// <param name="pass">The shader pass index to use, or -1 to execute all passes.</param>
+    /// <returns>An <see cref="IDisposable"/> registration handle that unregisters the hook when disposed.</returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="material"/> is null.</exception>
+    public static IDisposable AddGlobalFrameHook(Material material, int pass = -1)
+    {
+        if (material is null) throw new ArgumentNullException(nameof(material));
+        var reg = new GlobalHookRegistration(material, context => context.Blit(material, pass));
+        lock (GlobalHooksLock)
+        {
+            GlobalFrameHooks.Add(reg);
+            _globalHooksVersion++;
+        }
+        return reg;
+    }
+
+    /// <summary>
+    /// Registers a global frame modification hook implementing <see cref="IFrameHook"/>.
+    /// </summary>
+    /// <param name="hook">The hook instance to execute.</param>
+    /// <returns>An <see cref="IDisposable"/> registration handle that unregisters the hook when disposed.</returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="hook"/> is null.</exception>
+    public static IDisposable AddGlobalFrameHook(IFrameHook hook)
+    {
+        if (hook == null) throw new ArgumentNullException(nameof(hook));
+        var reg = new GlobalHookRegistration(hook, hook.OnRenderFrame);
+        lock (GlobalHooksLock)
+        {
+            GlobalFrameHooks.Add(reg);
+            _globalHooksVersion++;
+        }
+        return reg;
+    }
+
+    /// <summary>
+    /// Unregisters a previously registered global frame modification hook.
+    /// </summary>
+    /// <param name="hook">The hook action to remove.</param>
+    /// <returns><c>true</c> if the hook was successfully removed; otherwise, <c>false</c>.</returns>
+    public static bool RemoveGlobalFrameHook(Action<FrameHookContext> hook)
+    {
+        lock (GlobalHooksLock)
+        {
+            var idx = GlobalFrameHooks.FindIndex(r => ReferenceEquals(r.Key, hook) || Equals(r.Action, hook));
+            if (idx >= 0)
+            {
+                GlobalFrameHooks.RemoveAt(idx);
+                _globalHooksVersion++;
+                return true;
+            }
+            return false;
+        }
+    }
+
+    /// <summary>
+    /// Unregisters a previously registered global material-based post-processing pass.
+    /// </summary>
+    /// <param name="material">The material to remove.</param>
+    /// <returns><c>true</c> if any hooks matching <paramref name="material"/> were removed; otherwise, <c>false</c>.</returns>
+    public static bool RemoveGlobalFrameHook(Material material)
+    {
+        lock (GlobalHooksLock)
+        {
+            var removed = false;
+            for (var i = GlobalFrameHooks.Count - 1; i >= 0; i--)
+            {
+                if (ReferenceEquals(GlobalFrameHooks[i].Key, material))
+                {
+                    GlobalFrameHooks.RemoveAt(i);
+                    removed = true;
+                }
+            }
+            if (removed)
+            {
+                _globalHooksVersion++;
+            }
+            return removed;
+        }
+    }
+
+    /// <summary>
+    /// Unregisters a previously registered global frame modification hook implementing <see cref="IFrameHook"/>.
+    /// </summary>
+    /// <param name="hook">The hook instance to remove.</param>
+    /// <returns><c>true</c> if the hook was successfully removed; otherwise, <c>false</c>.</returns>
+    public static bool RemoveGlobalFrameHook(IFrameHook hook)
+    {
+        lock (GlobalHooksLock)
+        {
+            var idx = GlobalFrameHooks.FindIndex(r => ReferenceEquals(r.Key, hook));
+            if (idx >= 0)
+            {
+                GlobalFrameHooks.RemoveAt(idx);
+                _globalHooksVersion++;
+                return true;
+            }
+            return false;
+        }
+    }
+
+    private static void RemoveGlobalRegistration(GlobalHookRegistration registration)
+    {
+        lock (GlobalHooksLock)
+        {
+            if (GlobalFrameHooks.Remove(registration))
+            {
+                _globalHooksVersion++;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Clears all registered global frame modification hooks.
+    /// </summary>
+    public static void ClearGlobalFrameHooks()
+    {
+        lock (GlobalHooksLock)
+        {
+            if (GlobalFrameHooks.Count > 0)
+            {
+                GlobalFrameHooks.Clear();
+                _globalHooksVersion++;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Indicates whether any global frame modification hooks are currently registered.
+    /// </summary>
+    public static bool HasGlobalFrameHooks
+    {
+        get
+        {
+            lock (GlobalHooksLock)
+            {
+                return GlobalFrameHooks.Count > 0;
+            }
+        }
+    }
+
+    /// <summary>
+    /// The number of currently registered global frame modification hooks.
+    /// </summary>
+    public static int GlobalFrameHookCount
+    {
+        get
+        {
+            lock (GlobalHooksLock)
+            {
+                return GlobalFrameHooks.Count;
+            }
+        }
+    }
+
+    internal static int GlobalHooksVersion
+    {
+        get
+        {
+            lock (GlobalHooksLock)
+            {
+                return _globalHooksVersion;
+            }
+        }
+    }
+
+    internal static void CopyGlobalFrameHooksTo(List<Action<FrameHookContext>> destination)
+    {
+        lock (GlobalHooksLock)
+        {
+            for (var i = 0; i < GlobalFrameHooks.Count; i++)
+            {
+                destination.Add(GlobalFrameHooks[i].Action);
+            }
+        }
+    }
+
     /// <summary>
     /// Applies the configured flags and initiates the render session.
     /// </summary>
@@ -143,6 +509,15 @@ public class RenderSession
         if (_endCondition is not null) RenderContext.EndCondition = _endCondition;
         if (_onComplete is not null) RenderContext.OnComplete = _onComplete;
         if (_onLastUpdate is not null) RenderContext.OnLastUpdate = _onLastUpdate;
+
+        RenderContext.SessionFrameHooks.Clear();
+        if (_frameHooks.Count > 0)
+        {
+            foreach (var t in _frameHooks)
+            {
+                RenderContext.SessionFrameHooks.Add(t.Action);
+            }
+        }
         
         RenderManager.Instance.levelPath = levelPath;
         RenderManager.Instance.Configuration = renderConfig;

Core/FrameHookPipeline.cs

@@ -0,0 +1,189 @@
+using System;
+using System.Collections.Generic;
+using ADOFAIRenderer.API;
+using MelonLoader;
+using UnityEngine;
+
+namespace ADOFAIRenderer.Core;
+
+internal class FrameHookPipeline : IDisposable
+{
+    private RenderTexture? _pingRT;
+    private RenderTexture? _pongRT;
+    private RenderTexture? _lastOutputRT;
+    private FrameHookContext? _reusableContext;
+    private int _width;
+    private int _height;
+    private RenderTextureFormat _format;
+
+    public RenderTexture? Process(
+        RenderTexture sourceTexture,
+        long frameIndex,
+        long renderFrameIndex,
+        double videoTime,
+        double renderFps,
+        double videoFps,
+        IReadOnlyList<Action<FrameHookContext>> hooks)
+    {
+        if (hooks.Count == 0 || !sourceTexture || !sourceTexture.IsCreated())
+            return sourceTexture;
+
+        EnsureBuffers(sourceTexture);
+
+        if (!_pingRT || !_pongRT || !_pingRT.IsCreated() || !_pongRT.IsCreated())
+            return sourceTexture;
+
+        var prevActive = RenderTexture.active;
+        try
+        {
+            // Inter-frame ping-pong safety: start with the buffer that was NOT used as the output
+            // of the previous frame, ensuring the buffer currently being read back is not immediately overwritten.
+            var firstDestination = _lastOutputRT == _pingRT ? _pongRT : _pingRT;
+
+            if (_reusableContext == null)
+            {
+                _reusableContext = new FrameHookContext(
+                    sourceTexture,
+                    _pingRT,
+                    _pongRT,
+                    firstDestination,
+                    frameIndex,
+                    renderFrameIndex,
+                    videoTime,
+                    renderFps,
+                    videoFps
+                );
+            }
+            else
+            {
+                _reusableContext.Reset(
+                    sourceTexture,
+                    _pingRT,
+                    _pongRT,
+                    firstDestination,
+                    frameIndex,
+                    renderFrameIndex,
+                    videoTime,
+                    renderFps,
+                    videoFps
+                );
+            }
+
+            for (var i = 0; i < hooks.Count; i++)
+            {
+                try
+                {
+                    hooks[i](_reusableContext);
+                }
+                catch (Exception ex)
+                {
+                    Melon<RenderMod>.Logger.Error($"[FrameHook] Error executing frame hook #{i} on frame {frameIndex}: {ex}");
+                }
+            }
+
+            var result = _reusableContext.Current;
+            _lastOutputRT = _reusableContext.HasModified ? result : null;
+            return result;
+        }
+        finally
+        {
+            RenderTexture.active = prevActive;
+        }
+    }
+
+    private void EnsureBuffers(RenderTexture sourceTexture)
+    {
+        var width = sourceTexture.width;
+        var height = sourceTexture.height;
+        var format = sourceTexture.format;
+
+        if (_pingRT && _pongRT &&
+            _width == width && _height == height && _format == format &&
+            _pingRT.IsCreated() && _pongRT.IsCreated())
+        {
+            return;
+        }
+
+        ReleaseBuffers();
+
+        _width = width;
+        _height = height;
+        _format = format;
+
+        try
+        {
+            var desc = sourceTexture.descriptor;
+            desc.depthBufferBits = 0;
+            desc.msaaSamples = 1;
+            desc.useMipMap = false;
+            desc.autoGenerateMips = false;
+
+            var supportsUav = SystemInfo.supportsComputeShaders &&
+                              SystemInfo.SupportsRandomWriteOnRenderTextureFormat(desc.colorFormat);
+            desc.enableRandomWrite = supportsUav;
+
+            _pingRT = new RenderTexture(desc)
+            {
+                name = "ADOFAIRenderer_PingBuffer",
+                filterMode = sourceTexture.filterMode,
+                wrapMode = sourceTexture.wrapMode
+            };
+            _pingRT.Create();
+
+            _pongRT = new RenderTexture(desc)
+            {
+                name = "ADOFAIRenderer_PongBuffer",
+                filterMode = sourceTexture.filterMode,
+                wrapMode = sourceTexture.wrapMode
+            };
+            _pongRT.Create();
+        }
+        catch (Exception ex)
+        {
+            ReleaseBuffers();
+            Melon<RenderMod>.Logger.Warning($"[FrameHook] Failed to create descriptor-based PingPong RTs: {ex.Message}. Falling back to standard ARGB32.");
+            _pingRT = new RenderTexture(width, height, 0, RenderTextureFormat.ARGB32)
+            {
+                name = "ADOFAIRenderer_PingBuffer",
+                filterMode = sourceTexture.filterMode,
+                wrapMode = sourceTexture.wrapMode
+            };
+            _pingRT.Create();
+
+            _pongRT = new RenderTexture(width, height, 0, RenderTextureFormat.ARGB32)
+            {
+                name = "ADOFAIRenderer_PongBuffer",
+                filterMode = sourceTexture.filterMode,
+                wrapMode = sourceTexture.wrapMode
+            };
+            _pongRT.Create();
+        }
+    }
+
+    public void ReleaseBuffers()
+    {
+        if (_pingRT)
+        {
+            if (_pingRT.IsCreated()) _pingRT.Release();
+            UnityEngine.Object.Destroy(_pingRT);
+            _pingRT = null;
+        }
+
+        if (_pongRT)
+        {
+            if (_pongRT.IsCreated()) _pongRT.Release();
+            UnityEngine.Object.Destroy(_pongRT);
+            _pongRT = null;
+        }
+
+        _width = 0;
+        _height = 0;
+        _lastOutputRT = null;
+        _reusableContext = null;
+    }
+
+    public void Dispose()
+    {
+        ReleaseBuffers();
+    }
+}

Core/RenderManager.cs

@@ -37,6 +37,7 @@ internal static class RenderContext
     public static string? OutputPath;
         
     public static bool Notification = true;
+    public static readonly List<Action<FrameHookContext>> SessionFrameHooks = new();
         
     private static readonly Func<bool> EndConditionDefault = () => scrController.instance.state == States.Won;
     public static Func<bool> EndCondition = EndConditionDefault;
@@ -64,6 +65,7 @@ internal static class RenderContext
         OutputPath = null;
 
         Notification = true;
+        SessionFrameHooks.Clear();
             
         EndCondition = EndConditionDefault;
         OnComplete = OnCompleteDefault;
@@ -103,6 +105,49 @@ internal class RenderManager : MonoBehaviour
     private AudioSyncCalculator SyncCalculator { get; set; } = null!;
 
     private FrameReader? _frameReader;
+    private FrameHookPipeline? _frameHookPipeline;
+    private readonly List<Action<FrameHookContext>> _activeHooksCache = new();
+    private int _cachedGlobalHooksVersion = -1;
+    private bool _hasActiveHooksCached;
+
+    public bool HasActiveFrameHooks
+    {
+        get
+        {
+            EnsureActiveHooksUpToDate();
+            return _hasActiveHooksCached;
+        }
+    }
+
+    private void EnsureActiveHooksUpToDate()
+    {
+        var globalVersion = RenderSession.GlobalHooksVersion;
+        if (_cachedGlobalHooksVersion == globalVersion) return;
+
+        _cachedGlobalHooksVersion = globalVersion;
+        _activeHooksCache.Clear();
+        if (RenderContext.SessionFrameHooks.Count > 0)
+        {
+            _activeHooksCache.AddRange(RenderContext.SessionFrameHooks);
+        }
+        RenderSession.CopyGlobalFrameHooksTo(_activeHooksCache);
+        _hasActiveHooksCached = _activeHooksCache.Count > 0;
+    }
+
+    private List<Action<FrameHookContext>> GetActiveFrameHooks()
+    {
+        EnsureActiveHooksUpToDate();
+        return _activeHooksCache;
+    }
+
+    private void ResetFrameHookState()
+    {
+        _frameHookPipeline?.Dispose();
+        _frameHookPipeline = null;
+        _activeHooksCache.Clear();
+        _cachedGlobalHooksVersion = -1;
+        _hasActiveHooksCached = false;
+    }
 
     public long frameCountForVideo;
     public long lastVideoFrameIndex = -1;
@@ -160,6 +205,8 @@ internal class RenderManager : MonoBehaviour
             
         AudioSpectrumGenerator.Clear();
 
+        ResetFrameHookState();
+
         if (_activeVideoFFmpeg != null)
         {
             Melon<RenderMod>.Logger.Msg("Game exit or RenderManager destruction detected: Disposing FFmpeg native encoder resources.");
@@ -316,7 +363,23 @@ internal class RenderManager : MonoBehaviour
         {
             lastVideoFrameIndex = videoFrameIndex;
             lastRequestedVideoFrameIndex = videoFrameIndex;
-            _frameReader?.RequestFrameCapture(texture, videoFrameIndex);
+
+            var targetTexture = texture;
+            if (HasActiveFrameHooks && _frameHookPipeline != null)
+            {
+                var videoTime = effectiveVideoFps > 0 ? videoFrameIndex / effectiveVideoFps : 0.0;
+                targetTexture = _frameHookPipeline.Process(
+                    texture,
+                    videoFrameIndex,
+                    currentFrame,
+                    videoTime,
+                    renderFPS,
+                    effectiveVideoFps,
+                    GetActiveFrameHooks()
+                ) ?? texture;
+            }
+
+            _frameReader?.RequestFrameCapture(targetTexture, videoFrameIndex);
         }
     }
 
@@ -387,6 +450,10 @@ internal class RenderManager : MonoBehaviour
             
         _frameReader?.Dispose();
         _frameReader = null;
+        _frameHookPipeline?.Dispose();
+        _frameHookPipeline = new FrameHookPipeline();
+        _cachedGlobalHooksVersion = -1;
+        EnsureActiveHooksUpToDate();
         try
         {
             StartFFmpegThread();
@@ -395,6 +462,7 @@ internal class RenderManager : MonoBehaviour
         catch (Exception ex)
         {
             Melon<RenderMod>.Logger.Error($"Encoder initialization error: {ex}");
+            ResetFrameHookState();
             CommonWarningDialogUI.ShowDialog(
                 "Encoder Error",
                 $"Failed to initialize video encoder.\nError: {ex.Message}",
@@ -687,6 +755,7 @@ internal class RenderManager : MonoBehaviour
             }
                 
             _frameReader?.Dispose();
+            ResetFrameHookState();
 
             // Clean up Debug Monitor UI
             if (_debugMonitorObj)
@@ -776,6 +845,7 @@ internal class RenderManager : MonoBehaviour
         }
 
         _frameReader?.Dispose();
+        ResetFrameHookState();
         AudioMixer?.Reset(); AudioMixer = null;
         SyncCalculator.Reset();