shader mirror reflection: reduce reflections

// two texture cards: full thing Subshader { Pass { SetTexture[_MainTex] { combine texture } SetTexture[_ReflectionTex] { matrix [_ProjMatrix] combine texture * previous } } }

// fallback: just main texture Subshader { Pass { SetTexture [_MainTex] { combine texture } } }

// This is in fact just the Water script from Pro Standard Assets, // just with refraction stuff removed.

[ExecuteInEditMode] // Make mirror live-update even when not in play mode public class MirrorReflection : MonoBehaviour { public bool m_DisablePixelLights = true; public int m_TextureSize = 256; public float m_ClipPlaneOffset = 0.07f;

 public LayerMask m_ReflectLayers = -1;

 private Hashtable m_ReflectionCameras = new Hashtable(); // Camera -> Camera table

 private RenderTexture m_ReflectionTexture = null;
 private int m_OldReflectionTextureSize = 0;

 private static bool s_InsideRendering = false;

 // This is called when it's known that the object will be rendered by some
 // camera. We render reflections and do other updates here.
 // Because the script executes in edit mode, reflections for the scene view
 // camera will just work!
 public void OnWillRenderObject()
 {
     if( !enabled || !renderer || !renderer.sharedMaterial || !renderer.enabled )
         return;

     Camera cam = Camera.current;
     if( !cam )
         return;

     // Safeguard from recursive reflections.        
     if( s_InsideRendering )
         return;
     s_InsideRendering = true;

     Camera reflectionCamera;
     CreateMirrorObjects( cam, out reflectionCamera );

     // find out the reflection plane: position and normal in world space
     Vector3 pos = transform.position;
     Vector3 normal = transform.up;

     // Optionally disable pixel lights for reflection
     int oldPixelLightCount = QualitySettings.pixelLightCount;
     if( m_DisablePixelLights )
         QualitySettings.pixelLightCount = 0;

     UpdateCameraModes( cam, reflectionCamera );

     // Render reflection
     // Reflect camera around reflection plane
     float d = -Vector3.Dot (normal, pos) - m_ClipPlaneOffset;
     Vector4 reflectionPlane = new Vector4 (normal.x, normal.y, normal.z, d);

     Matrix4x4 reflection = Matrix4x4.zero;
     CalculateReflectionMatrix (ref reflection, reflectionPlane);
     Vector3 oldpos = cam.transform.position;
     Vector3 newpos = reflection.MultiplyPoint( oldpos );
     reflectionCamera.worldToCameraMatrix = cam.worldToCameraMatrix * reflection;

     // Setup oblique projection matrix so that near plane is our reflection
     // plane. This way we clip everything below/above it for free.
     Vector4 clipPlane = CameraSpacePlane( reflectionCamera, pos, normal, 1.0f );
     Matrix4x4 projection = cam.projectionMatrix;
     CalculateObliqueMatrix (ref projection, clipPlane);
     reflectionCamera.projectionMatrix = projection;

     reflectionCamera.cullingMask = ~(1<<4) & m_ReflectLayers.value; // never render water layer
     reflectionCamera.targetTexture = m_ReflectionTexture;
     GL.SetRevertBackfacing (true);
     reflectionCamera.transform.position = newpos;
     Vector3 euler = cam.transform.eulerAngles;
     reflectionCamera.transform.eulerAngles = new Vector3(0, euler.y, euler.z);
     reflectionCamera.Render();
     reflectionCamera.transform.position = oldpos;
     GL.SetRevertBackfacing (false);
     Material[] materials = renderer.sharedMaterials;
     foreach( Material mat in materials ) {
         if( mat.HasProperty("_ReflectionTex") )
             mat.SetTexture( "_ReflectionTex", m_ReflectionTexture );
     }

     // Set matrix on the shader that transforms UVs from object space into screen
     // space. We want to just project reflection texture on screen.
     Matrix4x4 scaleOffset = Matrix4x4.TRS(
         new Vector3(0.5f,0.5f,0.5f), Quaternion.identity, new Vector3(0.5f,0.5f,0.5f) );
     Vector3 scale = transform.lossyScale;
     Matrix4x4 mtx = transform.localToWorldMatrix * Matrix4x4.Scale( new Vector3(1.0f/scale.x, 1.0f/scale.y, 1.0f/scale.z) );
     mtx = scaleOffset * cam.projectionMatrix * cam.worldToCameraMatrix * mtx;
     foreach( Material mat in materials ) {
         mat.SetMatrix( "_ProjMatrix", mtx );
     }

     // Restore pixel light count
     if( m_DisablePixelLights )
         QualitySettings.pixelLightCount = oldPixelLightCount;

     s_InsideRendering = false;
 }


 // Cleanup all the objects we possibly have created
 void OnDisable()
 {
     if( m_ReflectionTexture ) {
         DestroyImmediate( m_ReflectionTexture );
         m_ReflectionTexture = null;
     }
     foreach( DictionaryEntry kvp in m_ReflectionCameras )
         DestroyImmediate( ((Camera)kvp.Value).gameObject );
     m_ReflectionCameras.Clear();
 }


 private void UpdateCameraModes( Camera src, Camera dest )
 {
     if( dest == null )
         return;
     // set camera to clear the same way as current camera
     dest.clearFlags = src.clearFlags;
     dest.backgroundColor = src.backgroundColor;        
     if( src.clearFlags == CameraClearFlags.Skybox )
     {
         Skybox sky = src.GetComponent(typeof(Skybox)) as Skybox;
         Skybox mysky = dest.GetComponent(typeof(Skybox)) as Skybox;
         if( !sky || !sky.material )
         {
             mysky.enabled = false;
         }
         else
         {
             mysky.enabled = true;
             mysky.material = sky.material;
         }
     }
     // update other values to match current camera.
     // even if we are supplying custom camera&projection matrices,
     // some of values are used elsewhere (e.g. skybox uses far plane)
     dest.farClipPlane = src.farClipPlane;
     dest.nearClipPlane = src.nearClipPlane;
     dest.orthographic = src.orthographic;
     dest.fieldOfView = src.fieldOfView;
     dest.aspect = src.aspect;
     dest.orthographicSize = src.orthographicSize;
 }

 // On-demand create any objects we need
 private void CreateMirrorObjects( Camera currentCamera, out Camera reflectionCamera )
 {
     reflectionCamera = null;

     // Reflection render texture
     if( !m_ReflectionTexture || m_OldReflectionTextureSize != m_TextureSize )
     {
         if( m_ReflectionTexture )
             DestroyImmediate( m_ReflectionTexture );
         m_ReflectionTexture = new RenderTexture( m_TextureSize, m_TextureSize, 16 );
         m_ReflectionTexture.name = "__MirrorReflection" + GetInstanceID();
         m_ReflectionTexture.isPowerOfTwo = true;
         m_ReflectionTexture.hideFlags = HideFlags.DontSave;
         m_OldReflectionTextureSize = m_TextureSize;
     }

     // Camera for reflection
     reflectionCamera = m_ReflectionCameras[currentCamera] as Camera;
     if( !reflectionCamera ) // catch both not-in-dictionary and in-dictionary-but-deleted-GO
     {
         GameObject go = new GameObject( "Mirror Refl Camera id" + GetInstanceID() + " for " + currentCamera.GetInstanceID(), typeof(Camera), typeof(Skybox) );
         reflectionCamera = go.camera;
         reflectionCamera.enabled = false;
         reflectionCamera.transform.position = transform.position;
         reflectionCamera.transform.rotation = transform.rotation;
         reflectionCamera.gameObject.AddComponent("FlareLayer");
         go.hideFlags = HideFlags.HideAndDontSave;
         m_ReflectionCameras[currentCamera] = reflectionCamera;
     }        
 }

 // Extended sign: returns -1, 0 or 1 based on sign of a
 private static float sgn(float a)
 {
     if (a > 0.0f) return 1.0f;
     if (a < 0.0f) return -1.0f;
     return 0.0f;
 }

 // Given position/normal of the plane, calculates plane in camera space.
 private Vector4 CameraSpacePlane (Camera cam, Vector3 pos, Vector3 normal, float sideSign)
 {
     Vector3 offsetPos = pos + normal * m_ClipPlaneOffset;
     Matrix4x4 m = cam.worldToCameraMatrix;
     Vector3 cpos = m.MultiplyPoint( offsetPos );
     Vector3 cnormal = m.MultiplyVector( normal ).normalized * sideSign;
     return new Vector4( cnormal.x, cnormal.y, cnormal.z, -Vector3.Dot(cpos,cnormal) );
 }

 // Adjusts the given projection matrix so that near plane is the given clipPlane
 // clipPlane is given in camera space. See article in Game Programming Gems 5.
 private static void CalculateObliqueMatrix (ref Matrix4x4 projection, Vector4 clipPlane)
 {
     Vector4 q = projection.inverse * new Vector4(
         sgn(clipPlane.x),
         sgn(clipPlane.y),
         1.0f,
         1.0f
     );
     Vector4 c = clipPlane * (2.0F / (Vector4.Dot (clipPlane, q)));
     // third row = clip plane - fourth row
     projection[2] = c.x - projection[3];
     projection[6] = c.y - projection[7];
     projection[10] = c.z - projection[11];
     projection[14] = c.w - projection[15];
 }

 // Calculates reflection matrix around the given plane
 private static void CalculateReflectionMatrix (ref Matrix4x4 reflectionMat, Vector4 plane)
 {
     reflectionMat.m00 = (1F - 2F*plane[0]*plane[0]);
     reflectionMat.m01 = (   - 2F*plane[0]*plane[1]);
     reflectionMat.m02 = (   - 2F*plane[0]*plane[2]);
     reflectionMat.m03 = (   - 2F*plane[3]*plane[0]);

     reflectionMat.m10 = (   - 2F*plane[1]*plane[0]);
     reflectionMat.m11 = (1F - 2F*plane[1]*plane[1]);
     reflectionMat.m12 = (   - 2F*plane[1]*plane[2]);
     reflectionMat.m13 = (   - 2F*plane[3]*plane[1]);

     reflectionMat.m20 = (   - 2F*plane[2]*plane[0]);
     reflectionMat.m21 = (   - 2F*plane[2]*plane[1]);
     reflectionMat.m22 = (1F - 2F*plane[2]*plane[2]);
     reflectionMat.m23 = (   - 2F*plane[3]*plane[2]);

     reflectionMat.m30 = 0F;
     reflectionMat.m31 = 0F;
     reflectionMat.m32 = 0F;
     reflectionMat.m33 = 1F;
 }