Unity3D shader——水的折射与反射

水的折射与反射原理其实差不多，只是一个用ComputeGrabScreenPos(o.pos)来取得贴图，一个用ComputeScreenPos(o.pos)来取得贴图。另外还需要两个脚本，一个是工具类的脚本，一个是得到反射贴图的脚本。 

这里直接放上核心源码：

Shader "GameCore/Mobile/Water/Diffuse"
{
Properties {
_BaseColor("BaseColor",color)=(1,1,1,1)
_MainTex("Texture",2D)="white"{}
_ReflectionTex("ReflectionTex",2D)=""{}
_Bias("Bias",range(0,1))=0
_Scale("Scale",range(0,1))=0
_Pow("Pow",range(0,5))=1
}
SubShader {
Tags {"RenderType"="Opaque" "Queue"="transparent"}

LOD 100
grabpass{}
Pass {
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
#include "Lighting.cginc"

float4 _BaseColor;
sampler2D _MainTex;
float4 _MainTex_ST;
sampler2D _GrabTexture;
sampler2D _ReflectionTex;
float _Bias,_Scale,_Pow;

struct v2f {
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
float4 proj:TEXCOORD1;
float4 refl:TEXCOORD2;
float3 L:TEXCOORD3;
float3 V:TEXCOORD4;
};

v2f vert(appdata_tan v){

v2f o;

o.pos=UnityObjectToClipPos(v.vertex);
o.uv=TRANSFORM_TEX(v.texcoord.xy,_MainTex);
o.proj=ComputeGrabScreenPos(o.pos);
o.refl=ComputeScreenPos(o.pos);
o.L=ObjSpaceLightDir(v.vertex);
o.V=ObjSpaceViewDir(v.vertex);

TANGENT_SPACE_ROTATION;
o.L=mul(rotation,o.L);
o.V=mul(rotation,o.V);

return o;
}

float4 frag(v2f IN):SV_Target{
float4 col1=tex2D(_MainTex,IN.uv+float2(_Time.x,0));
float4 col2=tex2D(_MainTex,float2(1-IN.uv.y,IN.uv.x)+float2(_Time.x,0)); //水的波动
float4 col=(col1+col2)/2;

float3 N=normalize(UnpackNormal(col));  //法向量
float off_xy=dot(N,float3(0,1,0));      //法向量和竖直方向向量的点积

IN.proj.xy+=off_xy*0.1;                //顶点加上偏移量
float4 gcol=tex2Dproj(_GrabTexture,IN.proj);  //折射效果

float diff=max(0,dot(N,normalize(IN.L)));  //法线与灯光的点积
float3 H=normalize(normalize(IN.L)+normalize(IN.V));
float spec=pow(max(0,dot(N,H)),128);   //高光效果

float4 diffCol=diff*_BaseColor;
diffCol.rgb+=spec*_LightColor0.rgb;
IN.refl.xy+=off_xy*0.3;
float4 reflcol=tex2Dproj(_ReflectionTex,IN.refl);
float4 fresnel=_Bias+_Scale*pow(1+dot(N,-normalize(IN.V)),_Pow);
float4 finalColor=lerp(gcol,reflcol,fresnel);
//fixed4 finalColor=lerp(fresnel,gcol,diffCol);
return finalColor;

}
ENDCG
}
}
}

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效果： 



其中：工具类脚本CodeTool.cs

using System.Collections;
using System;
using UnityEngine;

/// <summary>
/// 工具类
/// </summary>
public static class CoreTool
{
#region Config配置
/// <summary>
/// 验证当前文件是否为配置文件
/// </summary>
/// <param name="filePath">文件路径</param>
/// <returns></returns>
public static bool IsConfig(string filePath)
{
return true;
}
#endregion

#region Camera
/// <summary>
/// 将源摄像机状态克隆到目标相机
/// </summary>
/// <param name="src">源相机</param>
/// <param name="dest">目标相机</param>
public static void CloneCameraModes(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.depth = src.depth;
dest.farClipPlane = src.farClipPlane;
dest.nearClipPlane = src.nearClipPlane;
dest.orthographic = src.orthographic;
dest.fieldOfView = src.fieldOfView;
dest.aspect = src.aspect;
dest.orthographicSize = src.orthographicSize;
}

/// <summary>
/// 计算反射矩阵
/// </summary>
/// <param name="reflectionMat">原始矩阵</param>
/// <param name="plane">反射平面</param>
/// <returns>反射矩阵</returns>
public static Matrix4x4 CalculateReflectionMatrix(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;
return reflectionMat;
}

/// <summary>
/// 计算指定平面在摄像机中的空间位置
/// </summary>
/// <param name="cam">摄像机</param>
/// <param name="pos">平面上的点</param>
/// <param name="normal">平面法线</param>
/// <param name="sideSign">1：平面正面，-1：平面反面</param>
/// <param name="clipPlaneOffset">平面法线位置偏移量</param>
/// <returns></returns>
public static Vector4 CameraSpacePlane(Camera cam, Vector3 pos, Vector3 normal, float sideSign,float clipPlaneOffset)
{
Vector3 offsetPos = pos + normal * 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));
}

/// <summary>
/// 由剪裁面计算投影倾斜矩阵
/// </summary>
/// <param name="projection">投影矩阵</param>
/// <param name="clipPlane">剪裁面</param>
/// <param name="sideSign">剪裁平面(-1:平面下面,1:平面上面)</param>
public static Matrix4x4 CalculateObliqueMatrix(Matrix4x4 projection, Vector4 clipPlane,float sideSign)
{
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 + Mathf.Sign(sideSign)*projection[3];
projection[6] = c.y + Mathf.Sign(sideSign) * projection[7];
projection[10] = c.z + Mathf.Sign(sideSign) * projection[11];
projection[14] = c.w + Mathf.Sign(sideSign) * projection[15];
return projection;
}

private static float sgn(float a)
{
if (a > 0.0f) return 1.0f;
if (a < 0.0f) return -1.0f;
return 0.0f;
}

/// <summary>
/// 由水平、垂直距离修改倾斜矩阵
/// </summary>
/// <param name="projMatrix">倾斜矩阵</param>
/// <param name="horizObl">水平方向</param>
/// <param name="vertObl">垂直方向</param>
/// <returns>修改后的倾斜矩阵</returns>
public static Matrix4x4 CalculateObliqueMatrix(Matrix4x4 projMatrix, float horizObl, float vertObl)
{
Matrix4x4 mat = projMatrix;
mat[0, 2] = horizObl;
mat[1, 2] = vertObl;
return mat;
}
#endregion

#region Shader Matrix4x4
/// <summary>
/// tex2DProj到tex2D的uv纹理转换矩阵
/// 在shader中,
/// vert=>o.posProj = mul(_ProjMatrix, v.vertex);
/// frag=>tex2D(_RefractionTex,float2(i.posProj) / i.posProj.w)
/// </summary>
/// <param name="transform">要显示纹理的对象</param>
/// <param name="cam">当前观察的摄像机</param>
/// <returns>返回转换矩阵</returns>
public static Matrix4x4 UV_Tex2DProj2Tex2D(Transform transform,Camera cam)
{
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 _ProjMatrix = transform.localToWorldMatrix * Matrix4x4.Scale(new Vector3(1.0f / scale.x, 1.0f / scale.y, 1.0f / scale.z));
_ProjMatrix = scaleOffset * cam.projectionMatrix * cam.worldToCameraMatrix * _ProjMatrix;
return _ProjMatrix;
}
#endregion
}

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得到反射贴图的脚本：ReflectionEffect.cs

using UnityEngine;
using System.Collections;
using System;

/// <summary>
/// 反射效果
/// </summary>
[AddComponentMenu("GameCore/SpecialEffect/Reflection")]
[ExecuteInEditMode]
public class ReflectionEffect : MonoBehaviour
{
public Camera MainCamera;
public bool DisablePixelLights = true;
public int TextureSize = 512;
public float ClipPlaneOffset = 0;
public LayerMask 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 || !GetComponent<Renderer>() || !GetComponent<Renderer>().sharedMaterial || !GetComponent<Renderer>().enabled)
return;

Camera cam = MainCamera;
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 (DisablePixelLights)
QualitySettings.pixelLightCount = 0;

CoreTool.CloneCameraModes(cam, reflectionCamera);

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

Matrix4x4 reflection = CoreTool.CalculateReflectionMatrix(Matrix4x4.zero, 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 = CoreTool.CameraSpacePlane(reflectionCamera, pos, normal, 1.0f, ClipPlaneOffset);

Matrix4x4 projection = cam.projectionMatrix;

projection = CoreTool.CalculateObliqueMatrix(projection, clipPlane,1);

reflectionCamera.projectionMatrix = projection;

reflectionCamera.cullingMask = ~(1 << 4) & 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 = GetComponent<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 (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();
}

// 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 != TextureSize)
{
if (m_ReflectionTexture)
DestroyImmediate(m_ReflectionTexture);
m_ReflectionTexture = new RenderTexture(TextureSize, TextureSize,0);
m_ReflectionTexture.name = "__MirrorReflection" + GetInstanceID();
m_ReflectionTexture.isPowerOfTwo = true;
m_ReflectionTexture.hideFlags = HideFlags.DontSave;
m_ReflectionTexture.antiAliasing = 4;
m_ReflectionTexture.anisoLevel = 0;
m_OldReflectionTextureSize = 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.GetComponent<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;
}
}
}

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当然，以上的水的波纹可以按照需求调整。 

有一篇博客写得挺好的，那篇博客把波浪和水深的渐变加进去了，效果相当棒。如果用那篇文章的内容加上本篇的内容，基本上就把水的各种技术问题解决了。 
http://blog.csdn.net/mobilebbki399/article/details/50493117

最后的效果如下图：有波纹、有反射、折射、有浪花、有水深颜色渐变。