Unity3D--镜面反射

首先，新建一个Shader：

Shader "FX/Mirror Reflection"{
Properties {
_MainTex (“Base (RGB)”, 2D) = “white” {}
_ReflectionTex (“Reflection”, 2D) = “white” { TexGen ObjectLinear }
}
// 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 }
}
}
}

 

第二，新建一个脚本MirrorReflection.cs:

注意：被赋予脚本的物体不能缩放也就是物体的Rransform.scale的值均为1。

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()
{
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;
}
}