Change how loading screen fade works

Based on mosirnik/KK_MainGameVR

MainGameVR/Features/VRFade.cs

@@ -1,22 +1,27 @@
-using UnityEngine;
+using System;
+using System.Collections;
+using UnityEngine;
+using Valve.VR;
 using VRGIN.Core;
-using VRGIN.Helpers;
 
 namespace KKS_VR.Features
 {
     /// <summary>
-    /// A VR fader that synchronizes with the fader of the base game.
+    /// A VR fader that replaces the fader of the base game.
     /// </summary>
     internal class VRFade : ProtectedBehaviour
     {
         /// <summary>
         /// Reference to the image used by the vanilla SceneFade object.
         /// </summary>
-        private CanvasGroup _vanillaImage;
+        private CanvasGroup _vanillaFade;
 
-        private Material _fadeMaterial;
-        private int _fadeMaterialColorID;
-        private float _alpha = 0f;
+        private readonly Color _fadeColor = Color.white;
+        private readonly float _gridFadeTime = 1;
+        private readonly float _fadeAlphaThresholdHigh = 0.9999f;
+        private readonly float _fadeAlphaThresholdLow = 0.0001f;
+
+        private bool _isFading;
 
         public static void Create()
         {
@@ -25,31 +30,91 @@ public static void Create()
 
         protected override void OnAwake()
         {
-            _vanillaImage = Manager.Scene.sceneFadeCanvas.canvasGroup;
-            _fadeMaterial = new Material(UnityHelper.GetShader("Custom/SteamVR_Fade"));
-            _fadeMaterialColorID = Shader.PropertyToID("fadeColor");
+            _vanillaFade = Manager.Scene.sceneFadeCanvas?.canvasGroup ?? throw new ArgumentNullException(nameof(_vanillaFade), "sceneFadeCanvas or canvasGroup is null");
+        }
+
+        protected override void OnUpdate()
+        {
+            if (!_isFading && _vanillaFade && _vanillaFade.alpha > _fadeAlphaThresholdLow)
+            {
+                StartCoroutine(DeepFadeCo());
+            }
         }
 
-        private void OnPostRender()
+        /// <summary>
+        /// A coroutine for entering "deep fade", where we cut to the compositor's grid and display some overlay.
+        /// Based on https://github.com/mosirnik/KK_MainGameVR/commit/12e435f1e9a70c7d7b5dd56de416d300a2836091
+        /// </summary>
+        private IEnumerator DeepFadeCo()
         {
-            if (_vanillaImage != null)
+            if (OpenVR.Overlay == null || _isFading)
+                yield break;
+
+            _isFading = true;
+
+            // Make the world outside of the game the same color as the loading screen instead of the headset default skybox
+            SetCompositorSkyboxOverride(_fadeColor);
+
+            var compositor = OpenVR.Compositor;
+            if (compositor != null)
+            {
+                // Fade the game out so the ouside world is now seen instead of the laggy loading screen
+                compositor.FadeGrid(_gridFadeTime, true);
+
+                // It looks like we need to pause rendering here, otherwise the
+                // compositor will automatically put us back from the grid.
+                SteamVR_Render.pauseRendering = true;
+            }
+
+            // Wait for the game to fully fade in
+            while (_vanillaFade.alpha <= _fadeAlphaThresholdHigh)
+            {
+                if (!_vanillaFade || _vanillaFade.alpha < _fadeAlphaThresholdLow)
+                    goto endEarly;
+
+                yield return null;
+            }
+
+            // Wait for the game to start fading out
+            while (_vanillaFade.alpha > _fadeAlphaThresholdHigh)
+            {
+                yield return null;
+            }
+
+            // Wait for things to settle down
+            yield return null;
+            yield return null;
+
+        endEarly:
+
+            // Let the game be rendered again and fade into it
+            SteamVR_Render.pauseRendering = false;
+            if (compositor != null)
             {
-                var fadeColor = _vanillaImage.alpha;
-                _alpha = Mathf.Max(_alpha - 0.05f, fadeColor); // Use at least 20 frames to fade out.
-                fadeColor = _alpha;
-                if (_alpha > 0.0001f)
-                {
-                    _fadeMaterial.SetColor(_fadeMaterialColorID, new Color(1, 1, 1, fadeColor));
-                    _fadeMaterial.SetPass(0);
-                    GL.Begin(GL.QUADS);
-
-                    GL.Vertex3(-1, -1, 0);
-                    GL.Vertex3(1, -1, 0);
-                    GL.Vertex3(1, 1, 0);
-                    GL.Vertex3(-1, 1, 0);
-                    GL.End();
-                }
+                compositor.FadeGrid(_gridFadeTime, false);
+                yield return new WaitForSeconds(_gridFadeTime);
             }
+
+            // Wait for the game to finish fading to make sure we are synchronized
+            while (_vanillaFade && _vanillaFade.alpha > _fadeAlphaThresholdLow)
+            {
+                yield return null;
+            }
+
+            SteamVR_Skybox.ClearOverride();
+
+            _isFading = false;
+        }
+
+        private static void SetCompositorSkyboxOverride(Color fadeColor)
+        {
+            var tex = new Texture2D(1, 1);
+            var color = fadeColor;
+            color.a = 1f;
+            tex.SetPixel(0, 0, color);
+            tex.Apply();
+            SteamVR_Skybox.SetOverride(tex, tex, tex, tex, tex, tex);
+            Destroy(tex);
         }
     }
 }