Dans cette vidéo je vous propose de créer un miroir trés rapidement grâce au Shader. Nous utiliserons un Plane afin de simuler le miroir.

Vous pouvez retrouver les scripts ci dessous utiliser dans cette vidéo (Source http://wiki.unity3d.com)

Shader "FX/MirrorReflection"
{
    Properties
    {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        [HideInInspector] _ReflectionTex ("", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100
 
        Pass {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 refl : TEXCOORD1;
                float4 pos : SV_POSITION;
            };
            float4 _MainTex_ST;
            v2f vert(float4 pos : POSITION, float2 uv : TEXCOORD0)
            {
                v2f o;
                o.pos = mul (UNITY_MATRIX_MVP, pos);
                o.uv = TRANSFORM_TEX(uv, _MainTex);
                o.refl = ComputeScreenPos (o.pos);
                return o;
            }
            sampler2D _MainTex;
            sampler2D _ReflectionTex;
            fixed4 frag(v2f i) : SV_Target
            {
                fixed4 tex = tex2D(_MainTex, i.uv);
                fixed4 refl = tex2Dproj(_ReflectionTex, UNITY_PROJ_COORD(i.refl));
                return tex * refl;
            }
            ENDCG
        }
    }
}

using UnityEngine;
using System.Collections;
 
// 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()
    {
        var rend = GetComponent<Renderer>();
        if (!enabled || !rend || !rend.sharedMaterial || !rend.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;
        Matrix4x4 projection = cam.CalculateObliqueMatrix(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 = rend.sharedMaterials;
        foreach( Material mat in materials ) {
            if( mat.HasProperty("_ReflectionTex") )
                mat.SetTexture( "_ReflectionTex", m_ReflectionTexture );
        }
 
        // 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) );
    }
 
    // 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;
    }
}