feat(Locomotion): option to add skybox texture to tunnel overlay cage

The view in which the Tunnel Overlay fades out to can now have a
Cubemap texture provided to display as a static skybox to provide a
better point of reference.

The Effect Color can also be used to tint the skybox texture if
required.

Thanks to @JWNJWN for the work on this!

Author: thestonefox

Assets/VRTK/Documentation/API.md

@@ -2552,6 +2552,7 @@ Applys a tunnel overlay effect to the active VR camera when the play area is mov
  * **Minimum Speed:** Minimum movement speed for the effect to activate.
  * **Maximum Speed:** Maximum movement speed where the effect will have its max settings applied.
  * **Effect Color:** The color to use for the tunnel effect.
+ * **Effect Skybox:** An optional skybox texture to use for the tunnel effect.
  * **Initial Effect Size:** The initial amount of screen coverage the tunnel to consume without any movement.
  * **Maximum Effect Size:** Screen coverage at the maximum tracked values.
  * **Feather Size:** Feather effect size around the cut-off as fraction of screen.

Assets/VRTK/Internal/Materials/Resources/TunnelOverlay.mat

@@ -22,6 +22,10 @@ Material:
         m_Texture: {fileID: 0}
         m_Scale: {x: 1, y: 1}
         m_Offset: {x: 0, y: 0}
+    - _SecondarySkyBox:
+        m_Texture: {fileID: 0}
+        m_Scale: {x: 1, y: 1}
+        m_Offset: {x: 0, y: 0}
     m_Floats:
     - _AngularVelocity: 0
     - _FeatherSize: 0.1

Assets/VRTK/Source/Scripts/Internal/Shaders/VRTK_TunnelEffect.shader

@@ -5,7 +5,8 @@
         _Color("Color Tint", Color) = (0,0,0,1)
         _MainTex ("Texture", 2D) = "white" {}
         _AngularVelocity ("Angular Velocity", Float) = 0
-        _FeatherSize ("FeatherSize", Float) = 0.1
+        _FeatherSize ("Feather Size", Float) = 0.1
+        _SecondarySkyBox("Cage SkyBox", Cube) = "" {}
     }
 
     SubShader
@@ -46,20 +47,28 @@
             float _AngularVelocity;
             float _FeatherSize;
             half4 _Color;
+            samplerCUBE _SecondarySkyBox;
+            float4x4 _EyeProjection[2];
+            float4x4 _EyeToWorld[2];
 
             fixed4 frag (v2f i) : SV_Target
             {
                 float2 uv = UnityStereoScreenSpaceUVAdjust(i.uv, _MainTex_ST);
                 fixed4 col = tex2D(_MainTex, uv);
-
                 float2 coords = (i.uv - 0.5) * 2;
-                float radius = length(coords) / 1.414214;
+                float4 viewPos = mul(_EyeProjection[unity_StereoEyeIndex], float4(coords, 0, 1));
+                viewPos.xyz /= viewPos.w;
+
+                float radius = length(viewPos.xy / (_ScreenParams.xy / 2)) / 2;
                 float avMin = (1 - _AngularVelocity) - _FeatherSize;
                 float avMax = (1 - _AngularVelocity) + _FeatherSize;
                 float t = saturate((radius - avMin) / (avMax - avMin));
-                return lerp(col, _Color, t);
-            }
 
+                float3 rayDir = mul(_EyeToWorld[unity_StereoEyeIndex], viewPos).xyz;
+                half4 skyData = texCUBE(_SecondarySkyBox, normalize(rayDir));
+
+                return lerp(col, skyData * _Color, t);
+            }
             ENDCG
         }
     }

Assets/VRTK/Source/Scripts/Locomotion/VRTK_TunnelOverlay.cs

@@ -30,6 +30,8 @@ public class VRTK_TunnelOverlay : MonoBehaviour
 
         [Tooltip("The color to use for the tunnel effect.")]
         public Color effectColor = Color.black;
+        [Tooltip("An optional skybox texture to use for the tunnel effect.")]
+        public Texture effectSkybox;
         [Tooltip("The initial amount of screen coverage the tunnel to consume without any movement.")]
         [Range(0f, 1f)]
         public float initialEffectSize = 0f;
@@ -43,6 +45,7 @@ public class VRTK_TunnelOverlay : MonoBehaviour
         public float smoothingTime = 0.15f;
 
         protected Transform headset;
+        protected Camera headsetCamera;
         protected Transform playarea;
         protected VRTK_TunnelEffect cameraEffect;
         protected float angularVelocity;
@@ -53,9 +56,11 @@ public class VRTK_TunnelOverlay : MonoBehaviour
         protected int shaderPropertyColor;
         protected int shaderPropertyAV;
         protected int shaderPropertyFeather;
+        protected int shaderPropertySkyboxTexture;
         protected Color originalColor;
         protected float originalAngularVelocity;
         protected float originalFeatherSize;
+        protected Texture originalSkyboxTexture;
         protected float maximumEffectCoverage = 1.15f;
 
         protected virtual void Awake()
@@ -64,17 +69,25 @@ protected virtual void Awake()
             shaderPropertyColor = Shader.PropertyToID("_Color");
             shaderPropertyAV = Shader.PropertyToID("_AngularVelocity");
             shaderPropertyFeather = Shader.PropertyToID("_FeatherSize");
+            shaderPropertySkyboxTexture = Shader.PropertyToID("_SecondarySkyBox");
             VRTK_SDKManager.instance.AddBehaviourToToggleOnLoadedSetupChange(this);
         }
 
         protected virtual void OnEnable()
         {
             headset = VRTK_DeviceFinder.HeadsetCamera();
+            headsetCamera = headset.GetComponent<Camera>();
             playarea = VRTK_DeviceFinder.PlayAreaTransform();
             cameraEffect = headset.GetComponent<VRTK_TunnelEffect>();
             originalAngularVelocity = matCameraEffect.GetFloat(shaderPropertyAV);
             originalFeatherSize = matCameraEffect.GetFloat(shaderPropertyFeather);
             originalColor = matCameraEffect.GetColor(shaderPropertyColor);
+            CheckSkyboxTexture();
+            if (effectSkybox != null)
+            {
+                originalSkyboxTexture = matCameraEffect.GetTexture(shaderPropertySkyboxTexture);
+                matCameraEffect.SetTexture("_SecondarySkyBox", effectSkybox);
+            }
 
             if (cameraEffect == null)
             {
@@ -86,10 +99,14 @@ protected virtual void OnEnable()
         protected virtual void OnDisable()
         {
             headset = null;
+            headsetCamera = null;
             playarea = null;
 
             if (cameraEffect != null)
             {
+                matCameraEffect.SetTexture("_SecondarySkyBox", originalSkyboxTexture);
+                originalSkyboxTexture = null;
+
                 SetShaderFeather(originalColor, originalAngularVelocity, originalFeatherSize);
                 matCameraEffect.SetColor(shaderPropertyColor, originalColor);
                 Destroy(cameraEffect);
@@ -130,6 +147,25 @@ protected virtual void FixedUpdate()
 
             lastForward = fwd;
             lastPosition = pos;
+
+            if (effectSkybox != null)
+            {
+                matCameraEffect.SetMatrixArray("_EyeToWorld", new Matrix4x4[2]
+                {
+                headsetCamera.GetStereoViewMatrix(Camera.StereoscopicEye.Left).inverse,
+                headsetCamera.GetStereoViewMatrix(Camera.StereoscopicEye.Right).inverse
+                });
+
+                Matrix4x4[] eyeProjection = new Matrix4x4[2];
+                eyeProjection[0] = headsetCamera.GetStereoProjectionMatrix(Camera.StereoscopicEye.Left);
+                eyeProjection[1] = headsetCamera.GetStereoProjectionMatrix(Camera.StereoscopicEye.Right);
+                eyeProjection[0] = GL.GetGPUProjectionMatrix(eyeProjection[0], true).inverse;
+                eyeProjection[1] = GL.GetGPUProjectionMatrix(eyeProjection[1], true).inverse;
+                eyeProjection[0][1, 1] *= -1f;
+                eyeProjection[1][1, 1] *= -1f;
+
+                matCameraEffect.SetMatrixArray("_EyeProjection", eyeProjection);
+            }
         }
 
         protected virtual void SetShaderFeather(Color givenTunnelColor, float givenAngularVelocity, float givenFeatherSize)
@@ -138,5 +174,24 @@ protected virtual void SetShaderFeather(Color givenTunnelColor, float givenAngul
             matCameraEffect.SetFloat(shaderPropertyAV, givenAngularVelocity);
             matCameraEffect.SetFloat(shaderPropertyFeather, givenFeatherSize);
         }
+
+        protected virtual void CheckSkyboxTexture()
+        {
+            if (effectSkybox == null)
+            {
+                Cubemap tempTexture = new Cubemap(1, TextureFormat.ARGB32, false);
+                tempTexture.SetPixel(CubemapFace.NegativeX, 0, 0, Color.white);
+                tempTexture.SetPixel(CubemapFace.NegativeY, 0, 0, Color.white);
+                tempTexture.SetPixel(CubemapFace.NegativeZ, 0, 0, Color.white);
+                tempTexture.SetPixel(CubemapFace.PositiveX, 0, 0, Color.white);
+                tempTexture.SetPixel(CubemapFace.PositiveY, 0, 0, Color.white);
+                tempTexture.SetPixel(CubemapFace.PositiveZ, 0, 0, Color.white);
+                effectSkybox = tempTexture;
+            }
+            else if (effectColor.r < 0.15f && effectColor.g < 0.15 && effectColor.b < 0.15)
+            {
+                VRTK_Logger.Warn("`VRTK_TunnelOverlay` has an `Effect Skybox` texture but the `Effect Color` is too dark which will tint the texture so it is not visible.");
+            }
+        }
     }
 }