Mirror solution in URP

Hello,

I need a mirror solution for my archviz project, since Box Projection of Reflection Probes is not yet supported in URP I started to look for some custom scripts.
One that I found works in the editor but due to `Camera.Render()` call it gives "Recursive rendering is not supported in SRP (are you calling Camera.Render from within a render pipeline?)." Error.

I suspect that `ScriptableRendererFeature` may allow this script to work but I have no idea how it could be refactored.

I ask for help with achieving realistic mirror effect, possibly without spending any money.

Spoiler: Mirror Script

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3. using Varunit.Utility;
4.  
5. // This is in fact just the Water script from Pro Standard Assets,
6. // just with refraction stuff removed.
7. [ExecuteInEditMode] // Make mirror live-update even when not in play mode
8. public class MirrorReflection : MonoBehaviour
9. {
10.     [SerializeField, Collect]
11.     private Renderer _renderer;
12.  
13.     [SerializeField,TagSelector]
14.     private string _observerCameraTag;
15.  
16.     private Camera _observator;
17.  
18.     public bool m_DisablePixelLights = true;
19.     public int m_TextureSize = 256;
20.     public float m_ClipPlaneOffset = 0.07f;
21.  
22.     public LayerMask m_ReflectLayers = -1;
23.  
24.     private Hashtable m_ReflectionCameras = new Hashtable(); // Camera -> Camera table
25.  
26.     private RenderTexture m_ReflectionTexture = null;
27.     private int m_OldReflectionTextureSize = 0;
28.  
29.     private static bool s_InsideRendering = false;
30.  
31.     // This is called when it's known that the object will be rendered by some
32.     // camera. We render reflections and do other updates here.
33.     // Because the script executes in edit mode, reflections for the scene view
34.     // camera will just work!
35.     public void OnWillRenderObject()
36.     {
37.         if (!enabled || !_renderer || !_renderer.sharedMaterial || !_renderer.enabled)
38.             return;
39.      
40.         Camera cam = Camera.current;
41.         if (!cam)
42.             return;
43.  
44.         // Safeguard from recursive reflections.      
45.         if (s_InsideRendering)
46.             return;
47.         s_InsideRendering = true;
48.  
49.         Camera reflectionCamera;
50.         CreateMirrorObjects(cam, out reflectionCamera);
51.  
52.         // find out the reflection plane: position and normal in world space
53.         Vector3 pos = transform.position;
54.         Vector3 normal = transform.up;
55.  
56.         // Optionally disable pixel lights for reflection
57.         int oldPixelLightCount = QualitySettings.pixelLightCount;
58.         if (m_DisablePixelLights)
59.             QualitySettings.pixelLightCount = 0;
60.  
61.         UpdateCameraModes(cam, reflectionCamera);
62.  
63.         // Render reflection
64.         // Reflect camera around reflection plane
65.         float d = -Vector3.Dot(normal, pos) - m_ClipPlaneOffset;
66.         Vector4 reflectionPlane = new Vector4(normal.x, normal.y, normal.z, d);
67.  
68.         Matrix4x4 reflection = Matrix4x4.zero;
69.         CalculateReflectionMatrix(ref reflection, reflectionPlane);
70.         Vector3 oldpos = cam.transform.position;
71.         Vector3 newpos = reflection.MultiplyPoint(oldpos);
72.         reflectionCamera.worldToCameraMatrix = cam.worldToCameraMatrix * reflection;
73.  
74.         // Setup oblique projection matrix so that near plane is our reflection
75.         // plane. This way we clip everything below/above it for free.
76.         Vector4 clipPlane = CameraSpacePlane(reflectionCamera, pos, normal, 1.0f);
77.         //Matrix4x4 projection = cam.projectionMatrix;
78.         Matrix4x4 projection = cam.CalculateObliqueMatrix(clipPlane);
79.         reflectionCamera.projectionMatrix = projection;
80.  
81.         reflectionCamera.cullingMask = ~(1 << 4) & m_ReflectLayers.value; // never render water layer
82.         reflectionCamera.targetTexture = m_ReflectionTexture;
83.  
84.         GL.invertCulling = true;
85.  
86.         reflectionCamera.transform.position = newpos;
87.         Vector3 euler = cam.transform.eulerAngles;
88.         reflectionCamera.transform.eulerAngles = new Vector3(0, euler.y, euler.z);
89.         reflectionCamera.Render();
90.         reflectionCamera.transform.position = oldpos;
91.  
92.         GL.invertCulling = false;
93.  
94.         Material[] materials = _renderer.sharedMaterials;
95.         foreach (Material mat in materials)
96.         {
97.             if (mat.HasProperty("_ReflectionTex"))
98.                 mat.SetTexture("_ReflectionTex", m_ReflectionTexture);
99.         }
100.  
101.         // Restore pixel light count
102.         if (m_DisablePixelLights)
103.             QualitySettings.pixelLightCount = oldPixelLightCount;
104.  
105.         s_InsideRendering = false;
106.     }
107.  
108.  
109.     // Cleanup all the objects we possibly have created
110.     void OnDisable()
111.     {
112.         if (m_ReflectionTexture)
113.         {
114.             DestroyImmediate(m_ReflectionTexture);
115.             m_ReflectionTexture = null;
116.         }
117.         foreach (DictionaryEntry kvp in m_ReflectionCameras)
118.             DestroyImmediate(((Camera)kvp.Value).gameObject);
119.         m_ReflectionCameras.Clear();
120.     }
121.  
122.  
123.     private void UpdateCameraModes(Camera src, Camera dest)
124.     {
125.         if (dest == null)
126.             return;
127.         // set camera to clear the same way as current camera
128.         dest.clearFlags = src.clearFlags;
129.         dest.backgroundColor = src.backgroundColor;
130.         if (src.clearFlags == CameraClearFlags.Skybox)
131.         {
132.             Skybox sky = src.GetComponent(typeof(Skybox)) as Skybox;
133.             Skybox mysky = dest.GetComponent(typeof(Skybox)) as Skybox;
134.             if (!sky || !sky.material)
135.             {
136.                 mysky.enabled = false;
137.             }
138.             else
139.             {
140.                 mysky.enabled = true;
141.                 mysky.material = sky.material;
142.             }
143.         }
144.         // update other values to match current camera.
145.         // even if we are supplying custom camera&projection matrices,
146.         // some of values are used elsewhere (e.g. skybox uses far plane)
147.         dest.farClipPlane = src.farClipPlane;
148.         dest.nearClipPlane = src.nearClipPlane;
149.         dest.orthographic = src.orthographic;
150.         dest.fieldOfView = src.fieldOfView;
151.         dest.aspect = src.aspect;
152.         dest.orthographicSize = src.orthographicSize;
153.     }
154.  
155.     // On-demand create any objects we need
156.     private void CreateMirrorObjects(Camera currentCamera, out Camera reflectionCamera)
157.     {
158.         reflectionCamera = null;
159.  
160.         // Reflection render texture
161.         if (!m_ReflectionTexture || m_OldReflectionTextureSize != m_TextureSize)
162.         {
163.             if (m_ReflectionTexture)
164.                 DestroyImmediate(m_ReflectionTexture);
165.             m_ReflectionTexture = new RenderTexture(m_TextureSize, m_TextureSize, 16);
166.             m_ReflectionTexture.name = "__MirrorReflection" + GetInstanceID();
167.             m_ReflectionTexture.isPowerOfTwo = true;
168.             m_ReflectionTexture.hideFlags = HideFlags.DontSave;
169.             m_OldReflectionTextureSize = m_TextureSize;
170.         }
171.  
172.         // Camera for reflection
173.         reflectionCamera = m_ReflectionCameras[currentCamera] as Camera;
174.         if (!reflectionCamera) // catch both not-in-dictionary and in-dictionary-but-deleted-GO
175.         {
176.             GameObject go = new GameObject("Mirror Refl Camera id" + GetInstanceID() + " for " + currentCamera.GetInstanceID(), typeof(Camera), typeof(Skybox));
177.             reflectionCamera = go.GetComponent<Camera>();
178.             reflectionCamera.enabled = false;
179.             reflectionCamera.transform.position = transform.position;
180.             reflectionCamera.transform.rotation = transform.rotation;
181.             reflectionCamera.gameObject.AddComponent<FlareLayer>();
182.             reflectionCamera.transform.parent = transform;
183.             //go.hideFlags = HideFlags.HideAndDontSave;
184.             m_ReflectionCameras[currentCamera] = reflectionCamera;
185.         }
186.     }
187.  
188.     // Extended sign: returns -1, 0 or 1 based on sign of a
189.     private static float sgn(float a)
190.     {
191.         if (a > 0.0f) return 1.0f;
192.         if (a < 0.0f) return -1.0f;
193.         return 0.0f;
194.     }
195.  
196.     // Given position/normal of the plane, calculates plane in camera space.
197.     private Vector4 CameraSpacePlane(Camera cam, Vector3 pos, Vector3 normal, float sideSign)
198.     {
199.         Vector3 offsetPos = pos + normal * m_ClipPlaneOffset;
200.         Matrix4x4 m = cam.worldToCameraMatrix;
201.         Vector3 cpos = m.MultiplyPoint(offsetPos);
202.         Vector3 cnormal = m.MultiplyVector(normal).normalized * sideSign;
203.         return new Vector4(cnormal.x, cnormal.y, cnormal.z, -Vector3.Dot(cpos, cnormal));
204.     }
205.  
206.     // Calculates reflection matrix around the given plane
207.     private static void CalculateReflectionMatrix(ref Matrix4x4 reflectionMat, Vector4 plane)
208.     {
209.         reflectionMat.m00 = (1F - 2F * plane[0] * plane[0]);
210.         reflectionMat.m01 = (-2F * plane[0] * plane[1]);
211.         reflectionMat.m02 = (-2F * plane[0] * plane[2]);
212.         reflectionMat.m03 = (-2F * plane[3] * plane[0]);
213.  
214.         reflectionMat.m10 = (-2F * plane[1] * plane[0]);
215.         reflectionMat.m11 = (1F - 2F * plane[1] * plane[1]);
216.         reflectionMat.m12 = (-2F * plane[1] * plane[2]);
217.         reflectionMat.m13 = (-2F * plane[3] * plane[1]);
218.  
219.         reflectionMat.m20 = (-2F * plane[2] * plane[0]);
220.         reflectionMat.m21 = (-2F * plane[2] * plane[1]);
221.         reflectionMat.m22 = (1F - 2F * plane[2] * plane[2]);
222.         reflectionMat.m23 = (-2F * plane[3] * plane[2]);
223.  
224.         reflectionMat.m30 = 0F;
225.         reflectionMat.m31 = 0F;
226.         reflectionMat.m32 = 0F;
227.         reflectionMat.m33 = 1F;
228.     }
229. }

 

@ErnestSurys did you have any luck with fixing this? I'm having the same issue, but everything with the reflection still seems to work.

 

i would suggest to have a look into unity's boat attack demo which you can find on github.

 

hi have you found how to make mirror under URP?