BaseGamePerf: GC smoothing and Nature Renderer grass streaming caps

Spreads incremental GC across more frames and caps grass-cell work so
abrupt camera looks hitch less. Density, draw distance, and simulation
stay the same. Original values restore when the module is disabled.

README.md

@@ -19,6 +19,7 @@ I originally planned on releasing individual mods, but considering my workflow o
 | Map Module        | In-game map overlay and detachable popout window for a second monitor. Themes, custom colors, opacity controls, map rotation, track & industry labels, and optional MapEnhancer integration. |
 | Physics Optimizer | Cuts CPU spent on train physics (LOD fast-path + auto-freeze), with debug car tinting. Console: `/rpf` |
 | Mesh LOD          | Adds level-of-detail to rolling stock: distant cars progressively shed detail and finally collapse to a cheap proxy box, cutting triangle count on large saves. |
+| Base Game Performance | Smooths Unity's incremental garbage collector and Nature Renderer grass streaming to reduce camera-motion hitches without lowering visual quality. |
 | Profiler          | Unified in-game performance overlay: a frame-time graph plus live readouts that adapt to whichever optimization modules are enabled. Console: `/rpf overlay` |
 
 All modules are disabled by default; enable them per-module from the S³ settings page. A game restart is required for enable/disable to take effect. More modules will follow; S³ is designed to grow.
@@ -159,6 +160,20 @@ All three LOD reductions side by side, with the transition distances set artific
 
 ---
 
+## Base Game Performance
+
+Direct per-frame profiling found that the repeatable base-game stalls were garbage-collection
+frames rather than car culling, scenery loading, world streaming, or camera ground queries.
+This module reduces Unity's incremental GC slice from the game's 3 ms default to a configurable
+1 ms starting point. The work is spread across more frames, reducing individual stalls without
+changing resolution, shadows, draw distance, scenery, rolling-stock detail, or simulation.
+
+It can also cap Nature Renderer grass-cell streaming (instance budget, queued nearby loads,
+and staggered cell expiry) so abrupt camera looks hitch less. Density and draw distance stay
+the same. The original runtime values are restored immediately when the module is disabled.
+
+---
+
 ## Profiler
 
 A unified in-game performance overlay. It always shows a render + physics frame-time graph (render, FixedUpdate, Tick, and PosCars times) and a timing report, and it grows extra sections for whichever optimization modules are enabled:

src/Main.cs

@@ -32,6 +32,7 @@ public static class Main
         // constructor. Order here is display order in the settings panel.
         _registry.Register(new Modules.PhysicsOptimizer.PhysicsOptimizerModule());
         _registry.Register(new Modules.MeshLod.MeshLodModule());
+        _registry.Register(new Modules.BaseGamePerf.BaseGamePerfModule());
         _registry.Register(new Modules.Profiler.ProfilerModule());
         _registry.Register(new Modules.Popout.PopoutModule());
 

src/Modules/BaseGamePerf/BaseGamePerfModule.cs

@@ -0,0 +1,82 @@
+using S3.Core;
+using UnityEngine;
+using UnityEngine.Scripting;
+
+namespace S3.Modules.BaseGamePerf;
+
+public sealed class BaseGamePerfModule : IModule
+{
+    const string SettingsFile = "S3.basegame.json";
+
+    static bool _hasOriginal;
+    static ulong _originalSliceNanoseconds;
+
+    public static BaseGamePerfSettings Settings { get; private set; } = new();
+
+    public BaseGamePerfModule() =>
+        Settings = SettingsStore.Load<BaseGamePerfSettings>(SettingsFile);
+
+    public string Id => "basegame";
+    public string DisplayName => "Base Game Performance";
+    public string Description =>
+        "Evidence-backed vanilla-game hitch controls. Smooths incremental GC and " +
+        "Nature Renderer grass-cell streaming without reducing density, draw distance, " +
+        "resolution, or simulation quality.";
+
+    public bool Enabled
+    {
+        get => Settings.enabled;
+        set => Settings.enabled = value;
+    }
+
+    public void OnEnable()
+    {
+        if (!_hasOriginal)
+        {
+            _originalSliceNanoseconds = GarbageCollector.incrementalTimeSliceNanoseconds;
+            _hasOriginal = true;
+        }
+        try { NatureStreamingOptimizer.Enable(); }
+        catch (System.Exception ex)
+        {
+            Log.Warn(
+                "[basegame] Nature streaming smoothing unavailable: " +
+                ex.GetBaseException().Message);
+        }
+        ApplyRuntimeSettings();
+    }
+
+    public void OnDisable()
+    {
+        NatureStreamingOptimizer.Disable();
+        if (_hasOriginal)
+        {
+            GarbageCollector.incrementalTimeSliceNanoseconds = _originalSliceNanoseconds;
+            Log.Info(
+                $"[basegame] Restored incremental GC slice to " +
+                $"{_originalSliceNanoseconds / 1_000_000.0:0.###}ms.");
+        }
+    }
+
+    public static void ApplyRuntimeSettings()
+    {
+        if (!GarbageCollector.isIncremental)
+        {
+            Log.Warn("[basegame] Unity incremental GC is disabled; smoothing was not applied.");
+            return;
+        }
+
+        ulong desired = Settings.gcSmoothingEnabled
+            ? (ulong)(Mathf.Clamp(Settings.incrementalSliceMs, 0.25f, 5f) * 1_000_000f)
+            : _originalSliceNanoseconds;
+        GarbageCollector.incrementalTimeSliceNanoseconds = desired;
+        Log.Info(
+            $"[basegame] Incremental GC slice={desired / 1_000_000.0:0.###}ms " +
+            $"(smoothing={Settings.gcSmoothingEnabled}).");
+        NatureStreamingOptimizer.ApplySettings();
+    }
+
+    public void SaveSettings() => Persist();
+    public static void Persist() => SettingsStore.Save(SettingsFile, Settings);
+    public void DrawSettings() => BaseGamePerfSettingsUI.Draw();
+}

src/Modules/BaseGamePerf/BaseGamePerfSettings.cs

@@ -0,0 +1,16 @@
+using System;
+
+namespace S3.Modules.BaseGamePerf;
+
+[Serializable]
+public sealed class BaseGamePerfSettings
+{
+    public bool enabled = false;
+    public bool gcSmoothingEnabled = true;
+    public float incrementalSliceMs = 1f;
+    public bool natureStreamingSmoothingEnabled = true;
+    public int grassInstanceBudgetPerFrame = 256;
+    public bool queueNearbyGrassLoads = true;
+    public int grassUnloadSpreadFrames = 120;
+    public bool distanceCullNatureTerrains = false;
+}

src/Modules/BaseGamePerf/BaseGamePerfSettingsUI.cs

@@ -0,0 +1,112 @@
+using UnityEngine;
+
+namespace S3.Modules.BaseGamePerf;
+
+static class BaseGamePerfSettingsUI
+{
+    public static void Draw()
+    {
+        BaseGamePerfSettings s = BaseGamePerfModule.Settings;
+        bool changed = false;
+
+        GUILayout.BeginVertical();
+        GUILayout.Label("<b>Base Game Performance</b>  — conservative vanilla hitch controls");
+        GUILayout.Space(4f);
+        GUILayout.Label(
+            "  Smooths Unity's incremental garbage collection. This does not alter\n" +
+            "  resolution, shadows, draw distance, scenery, or rolling-stock detail.",
+            GUI.skin.label);
+        GUILayout.Space(8f);
+
+        bool enabled = GUILayout.Toggle(
+            s.gcSmoothingEnabled,
+            " Shorter incremental GC slices");
+        if (enabled != s.gcSmoothingEnabled)
+        {
+            s.gcSmoothingEnabled = enabled;
+            changed = true;
+        }
+
+        GUILayout.BeginHorizontal();
+        GUILayout.Label($"Slice budget:  {s.incrementalSliceMs:0.00}ms", GUILayout.Width(150f));
+        float slice = GUILayout.HorizontalSlider(
+            s.incrementalSliceMs, 0.25f, 3f, GUILayout.Width(200f));
+        GUILayout.EndHorizontal();
+        if (Mathf.Abs(slice - s.incrementalSliceMs) > 0.01f)
+        {
+            s.incrementalSliceMs = slice;
+            changed = true;
+        }
+
+        GUILayout.Label(
+            "  Lower values reduce individual GC stalls but spread collection work\n" +
+            "  across more frames. 1.00ms is the measured starting point.",
+            GUI.skin.label);
+        GUILayout.Space(10f);
+
+        bool nature = GUILayout.Toggle(
+            s.natureStreamingSmoothingEnabled,
+            " Smooth Nature Renderer grass streaming");
+        if (nature != s.natureStreamingSmoothingEnabled)
+        {
+            s.natureStreamingSmoothingEnabled = nature;
+            changed = true;
+        }
+
+        GUILayout.BeginHorizontal();
+        GUILayout.Label(
+            $"Grass load budget:  {s.grassInstanceBudgetPerFrame} instances/terrain",
+            GUILayout.Width(250f));
+        int grassBudget = Mathf.RoundToInt(GUILayout.HorizontalSlider(
+            s.grassInstanceBudgetPerFrame, 64f, 1024f, GUILayout.Width(200f)));
+        GUILayout.EndHorizontal();
+        if (grassBudget != s.grassInstanceBudgetPerFrame)
+        {
+            s.grassInstanceBudgetPerFrame = grassBudget;
+            changed = true;
+        }
+
+        bool queueNearby = GUILayout.Toggle(
+            s.queueNearbyGrassLoads,
+            " Queue nearby grass cells instead of force-loading them");
+        if (queueNearby != s.queueNearbyGrassLoads)
+        {
+            s.queueNearbyGrassLoads = queueNearby;
+            changed = true;
+        }
+
+        GUILayout.BeginHorizontal();
+        GUILayout.Label(
+            $"Grass unload spread:  {s.grassUnloadSpreadFrames} frames",
+            GUILayout.Width(250f));
+        int unloadSpread = Mathf.RoundToInt(GUILayout.HorizontalSlider(
+            s.grassUnloadSpreadFrames, 0f, 300f, GUILayout.Width(200f)));
+        GUILayout.EndHorizontal();
+        if (unloadSpread != s.grassUnloadSpreadFrames)
+        {
+            s.grassUnloadSpreadFrames = unloadSpread;
+            changed = true;
+        }
+
+        bool distanceCull = GUILayout.Toggle(
+            s.distanceCullNatureTerrains,
+            " Unload Nature Renderer data for distant terrain tiles (experimental)");
+        if (distanceCull != s.distanceCullNatureTerrains)
+        {
+            s.distanceCullNatureTerrains = distanceCull;
+            changed = true;
+        }
+
+        GUILayout.Label(
+            "  The default 256/120 settings preserve density and draw distance while\n" +
+            "  spreading cell uploads and expiry across frames. Distant-terrain\n" +
+            "  lifecycle is off by default until portal-camera visuals are validated.",
+            GUI.skin.label);
+        GUILayout.EndVertical();
+
+        if (!changed) return;
+        if (Main.Registry.IsActive("basegame"))
+            BaseGamePerfModule.ApplyRuntimeSettings();
+        BaseGamePerfModule.Persist();
+    }
+}

src/Modules/BaseGamePerf/NatureStreamingOptimizer.cs

@@ -0,0 +1,258 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using HarmonyLib;
+using S3.Core;
+using UnityEngine;
+using VisualDesignCafe.Rendering.Instancing;
+using VisualDesignCafe.Rendering.Nature;
+
+namespace S3.Modules.BaseGamePerf;
+
+/// <summary>
+/// Conservative smoothing for Nature Renderer's terrain-detail streaming.
+/// It changes scheduling and residency only; density, render distance,
+/// materials, shadows, and terrain content are untouched.
+/// </summary>
+static class NatureStreamingOptimizer
+{
+    sealed class RendererState
+    {
+        public WeakReference<NatureRenderer> Renderer = null!;
+        public bool OnlyInitializeWithinRenderingDistance;
+    }
+
+    static readonly Dictionary<int, RendererState> OriginalRenderers = new();
+    static readonly FieldInfo? RenderingDistanceLimitField =
+        AccessTools.Field(typeof(NatureRenderer), "_renderingDistanceLimit");
+    static readonly FieldInfo? StreamingBudgetField =
+        AccessTools.Field(typeof(TerrainGrassStreamer), "_globalStreamingBudget");
+    static readonly FieldInfo? ForceNearbyField =
+        AccessTools.Field(typeof(TerrainGrassStreamer), "_globalNearbyCellLoading");
+    static readonly FieldInfo? TimersField =
+        AccessTools.Field(typeof(TerrainGrassStreamer), "_inRangeOfAnyCamera");
+
+    static Harmony? _harmony;
+    static int _originalStreamingBudget = 1024;
+    static bool _originalForceNearby = true;
+
+    public static void Enable()
+    {
+        if (_harmony != null) return;
+        CaptureGrassGlobals();
+        _harmony = new Harmony("S3.basegame.nature");
+        _harmony.CreateClassProcessor(
+            typeof(GrassBudgetSetterPatch)).Patch();
+        _harmony.CreateClassProcessor(
+            typeof(GrassNearbySetterPatch)).Patch();
+        _harmony.CreateClassProcessor(
+            typeof(NatureRendererOnEnablePatch)).Patch();
+        _harmony.CreateClassProcessor(
+            typeof(NatureRendererRangePatch)).Patch();
+        _harmony.CreateClassProcessor(
+            typeof(TerrainGrassExpiryPatch)).Patch();
+        ApplySettings();
+    }
+
+    public static void Disable()
+    {
+        _harmony?.UnpatchAll("S3.basegame.nature");
+        _harmony = null;
+        RestoreRendererSettings();
+        try
+        {
+            TerrainGrassStreamer.SetStreamingBudget(_originalStreamingBudget);
+            TerrainGrassStreamer.SetForceLoadNearbyCells(_originalForceNearby);
+        }
+        catch { }
+    }
+
+    public static void ApplySettings()
+    {
+        BaseGamePerfSettings settings = BaseGamePerfModule.Settings;
+        if (!settings.natureStreamingSmoothingEnabled)
+        {
+            RestoreRendererSettings();
+            TerrainGrassStreamer.SetStreamingBudget(_originalStreamingBudget);
+            TerrainGrassStreamer.SetForceLoadNearbyCells(_originalForceNearby);
+            return;
+        }
+
+        TerrainGrassStreamer.SetStreamingBudget(
+            Mathf.Clamp(settings.grassInstanceBudgetPerFrame, 64, 4096));
+        TerrainGrassStreamer.SetForceLoadNearbyCells(
+            !settings.queueNearbyGrassLoads);
+
+        NatureRenderer[] renderers =
+            Resources.FindObjectsOfTypeAll<NatureRenderer>();
+        for (int i = 0; i < renderers.Length; i++)
+            TrackAndApply(renderers[i]);
+
+        Log.Info(
+            $"[basegame] Nature streaming: grassBudget=" +
+            $"{settings.grassInstanceBudgetPerFrame} instances/frame, " +
+            $"queueNearby={settings.queueNearbyGrassLoads}, " +
+            $"unloadSpread={settings.grassUnloadSpreadFrames} frames, " +
+            $"distanceLifecycle={settings.distanceCullNatureTerrains}, " +
+            $"terrains={OriginalRenderers.Count}.");
+    }
+
+    static void CaptureGrassGlobals()
+    {
+        try
+        {
+            if (StreamingBudgetField?.GetValue(null) is int budget)
+                _originalStreamingBudget = budget;
+            if (ForceNearbyField?.GetValue(null) is bool force)
+                _originalForceNearby = force;
+        }
+        catch { }
+    }
+
+    static void TrackAndApply(NatureRenderer? renderer)
+    {
+        if (renderer == null || !renderer.gameObject.scene.IsValid()) return;
+        int id = renderer.GetInstanceID();
+        if (!OriginalRenderers.ContainsKey(id))
+        {
+            OriginalRenderers[id] = new RendererState
+            {
+                Renderer = new WeakReference<NatureRenderer>(renderer),
+                OnlyInitializeWithinRenderingDistance =
+                    renderer.OnlyInitializeWithinRenderingDistance,
+            };
+        }
+        renderer.OnlyInitializeWithinRenderingDistance =
+            BaseGamePerfModule.Settings.distanceCullNatureTerrains;
+    }
+
+    static void RestoreRendererSettings()
+    {
+        foreach (RendererState state in OriginalRenderers.Values)
+        {
+            if (!state.Renderer.TryGetTarget(out NatureRenderer? renderer) ||
+                renderer == null)
+                continue;
+            renderer.OnlyInitializeWithinRenderingDistance =
+                state.OnlyInitializeWithinRenderingDistance;
+        }
+        OriginalRenderers.Clear();
+    }
+
+    static bool CorrectRangeCheck(
+        NatureRenderer renderer,
+        double threshold)
+    {
+        Terrain? terrain = renderer.Terrain;
+        TerrainData? data = renderer.TerrainData;
+        if (terrain == null || data == null) return false;
+
+        Bounds bounds = data.bounds;
+        bounds.center += terrain.GetPosition();
+        float configuredLimit = 5000f;
+        try
+        {
+            if (RenderingDistanceLimitField?.GetValue(renderer) is float value)
+                configuredLimit = value;
+        }
+        catch { }
+
+        foreach (CameraRenderer cameraRenderer in RendererPool.GetCameras())
+        {
+            Camera? camera = cameraRenderer?.Camera;
+            if (camera == null ||
+                camera.cameraType == CameraType.Preview ||
+                camera.cameraType == CameraType.SceneView)
+                continue;
+
+            Vector3 position = camera.transform.position;
+            Vector3 center = bounds.center;
+            Vector3 extents = bounds.extents;
+            double dx = Math.Max(
+                0.0, Math.Abs(position.x - center.x) - extents.x);
+            double dy = Math.Max(
+                0.0, Math.Abs(position.y - center.y) - extents.y);
+            double dz = Math.Max(
+                0.0, Math.Abs(position.z - center.z) - extents.z);
+            double distance = Math.Sqrt(dx * dx + dy * dy + dz * dz);
+            double limit = Math.Min(configuredLimit, camera.farClipPlane);
+            if (distance < limit + threshold) return true;
+        }
+        return false;
+    }
+
+    [HarmonyPatch(
+        typeof(TerrainGrassStreamer),
+        nameof(TerrainGrassStreamer.SetStreamingBudget))]
+    static class GrassBudgetSetterPatch
+    {
+        static void Prefix(ref int __0)
+        {
+            BaseGamePerfSettings settings = BaseGamePerfModule.Settings;
+            if (!settings.natureStreamingSmoothingEnabled) return;
+            __0 = Mathf.Min(
+                __0, Mathf.Clamp(settings.grassInstanceBudgetPerFrame, 64, 4096));
+        }
+    }
+
+    [HarmonyPatch(
+        typeof(TerrainGrassStreamer),
+        nameof(TerrainGrassStreamer.SetForceLoadNearbyCells))]
+    static class GrassNearbySetterPatch
+    {
+        static void Prefix(ref bool __0)
+        {
+            BaseGamePerfSettings settings = BaseGamePerfModule.Settings;
+            if (settings.natureStreamingSmoothingEnabled &&
+                settings.queueNearbyGrassLoads)
+                __0 = false;
+        }
+    }
+
+    [HarmonyPatch(typeof(NatureRenderer), "OnEnable")]
+    static class NatureRendererOnEnablePatch
+    {
+        static void Postfix(NatureRenderer __instance)
+        {
+            if (BaseGamePerfModule.Settings.natureStreamingSmoothingEnabled)
+                TrackAndApply(__instance);
+        }
+    }
+
+    [HarmonyPatch(typeof(NatureRenderer), "IsInRangeOfAnyCamera")]
+    static class NatureRendererRangePatch
+    {
+        static bool Prefix(
+            NatureRenderer __instance,
+            double __0,
+            ref bool __result)
+        {
+            BaseGamePerfSettings settings = BaseGamePerfModule.Settings;
+            if (!settings.natureStreamingSmoothingEnabled ||
+                !settings.distanceCullNatureTerrains)
+                return true;
+            __result = CorrectRangeCheck(__instance, __0);
+            return false;
+        }
+    }
+
+    [HarmonyPatch(typeof(TerrainGrassStreamer), "OnCellOutOfRange")]
+    static class TerrainGrassExpiryPatch
+    {
+        static void Postfix(TerrainGrassStreamer __instance, int __1)
+        {
+            BaseGamePerfSettings settings = BaseGamePerfModule.Settings;
+            int spread = Mathf.Clamp(settings.grassUnloadSpreadFrames, 0, 600);
+            if (!settings.natureStreamingSmoothingEnabled ||
+                spread <= 0 ||
+                TimersField?.GetValue(__instance) is not int[] timers ||
+                __1 < 0 ||
+                __1 >= timers.Length)
+                return;
+
+            int hash = unchecked(
+                __instance.GetHashCode() * 397 ^ __1 * 7919) & int.MaxValue;
+            timers[__1] += hash % (spread + 1);
+        }
+    }
+}

src/S3.csproj

@@ -29,6 +29,18 @@
       <HintPath>$(GameManaged)\Map.Runtime.dll</HintPath>
       <Private>false</Private>
     </Reference>
+    <Reference Include="Definition">
+      <HintPath>$(GameManaged)\Definition.dll</HintPath>
+      <Private>false</Private>
+    </Reference>
+    <Reference Include="VisualDesignCafe.Rendering.Nature">
+      <HintPath>$(GameManaged)\VisualDesignCafe.Rendering.Nature.dll</HintPath>
+      <Private>false</Private>
+    </Reference>
+    <Reference Include="VisualDesignCafe.Rendering.Instancing">
+      <HintPath>$(GameManaged)\VisualDesignCafe.Rendering.Instancing.dll</HintPath>
+      <Private>false</Private>
+    </Reference>
   </ItemGroup>
 
   <!-- Unity -->
@@ -49,6 +61,10 @@
       <HintPath>$(GameManaged)\UnityEngine.PhysicsModule.dll</HintPath>
       <Private>false</Private>
     </Reference>
+    <Reference Include="UnityEngine.TerrainModule">
+      <HintPath>$(GameManaged)\UnityEngine.TerrainModule.dll</HintPath>
+      <Private>false</Private>
+    </Reference>
     <Reference Include="UnityEngine.JSONSerializeModule">
       <HintPath>$(GameManaged)\UnityEngine.JSONSerializeModule.dll</HintPath>
       <Private>false</Private>
@@ -65,6 +81,10 @@
       <HintPath>$(GameManaged)\UnityEngine.InputLegacyModule.dll</HintPath>
       <Private>false</Private>
     </Reference>
+    <Reference Include="Unity.InputSystem">
+      <HintPath>$(GameManaged)\Unity.InputSystem.dll</HintPath>
+      <Private>false</Private>
+    </Reference>
     <Reference Include="Unity.TextMeshPro">
       <HintPath>$(GameManaged)\Unity.TextMeshPro.dll</HintPath>
       <Private>false</Private>
@@ -73,6 +93,14 @@
       <HintPath>$(GameManaged)\Unity.RenderPipelines.Universal.Runtime.dll</HintPath>
       <Private>false</Private>
     </Reference>
+    <Reference Include="UnityEngine.ImageConversionModule">
+      <HintPath>$(GameManaged)\UnityEngine.ImageConversionModule.dll</HintPath>
+      <Private>false</Private>
+    </Reference>
+    <Reference Include="UnityEngine.TextRenderingModule">
+      <HintPath>$(GameManaged)\UnityEngine.TextRenderingModule.dll</HintPath>
+      <Private>false</Private>
+    </Reference>
   </ItemGroup>
 
   <!-- UMM + Harmony -->
@@ -85,6 +113,10 @@
       <HintPath>$(UmmDir)\0Harmony.dll</HintPath>
       <Private>false</Private>
     </Reference>
+    <Reference Include="Newtonsoft.Json">
+      <HintPath>$(GameManaged)\Newtonsoft.Json.dll</HintPath>
+      <Private>false</Private>
+    </Reference>
   </ItemGroup>
 
 </Project>