unity自带的资源中有水的例子，导入步骤为：Assets-Import Package-Water (Pro Only)，熟悉相关参数就可以调出很漂亮的水效果，但是作为程序员不能只停留在使用层，了解其中的原理才是我们追寻的目标。
先看看效果，这样学习兴趣会更大。
因为unity自带demo集成的比较多，作为新手很难进行学习，所以就在网上先找关于反射的资料，不找不知道一找吓一跳，反射才不简单！不过现在不用看懂它会用就好，在这里反射被封装为一个名为Mirror的cs脚本，将这个脚本绑定到水的对象上就可以获取当前反射的贴图，然后将贴图传到shader中就可以显示。之前有接触过grabpass，法线贴图，所以现在只需要加上反射就能实现一个普通水的效果，显然通过设置参数这个shader还可以用于镜面反射，玻璃效果等等。而在这之前完全不懂这些是啥，所以获得经验：有规划的进行学习终究有所收获。
原理和shader代码如下(有不对的地方希望能指出)：
Shader "Mirrors/Transparent Bumped Specular Flat" {
Properties {
_Speed ("UV移动速度", Range (-1,1)) = 0
_Transparency("材质透明度", Range (0, 1)) = 1
_Distortion ("针对法线贴图的扭曲程度", range (0,0.4)) = 0
_Color ("主色", Color) = (1,1,1,1)
_MainTex ("主材质", 2D) = "white" {}
_BlendLevel("主材质显示强度",Range(0,1))=1
_SpecColor ("镜面颜色", Color) = (0.5, 0.5, 0.5, 1)
_Shininess ("镜面强度", Range (0.01, 1)) = 0.078125
_BumpMap ("法线贴图", 2D) = "bump" {}
_Bumpness ("法线颜色强度",Range(0,1))= 1
_Ref ("来自镜面反射", 2D) = "white" {}
}
SubShader {
Tags { "Queue"="Transparent" "RenderType"="Opaque" }
GrabPass {
Name "BASE"
Tags { "LightMode" = "Always" }
}
CGPROGRAM
#pragma surface surf BlinnPhong
#pragma target 3.0
half _Speed;// uv移动速度
half _Transparency;//材质透明度
half _Distortion;// 扭曲强度
fixed4 _Color;//主色
sampler2D _MainTex;// 主材质图
half _BlendLevel;// 主材质强度
half _Shininess;// 镜面强度
sampler2D _BumpMap;// 法线贴图
half _Bumpness;// 法线颜色强度
sampler2D _Ref;// 反射贴图
sampler2D _GrabTexture;// 屏幕纹理
struct Input {
float2 uv_MainTex;// 主贴图
float2 uv_BumpMap;// 法线贴图
float4 screenPos;// 顶点在屏幕坐标的位置
};
void surf (Input IN, inout SurfaceOutput o) {
// 移动法线纹理的X
IN.uv_BumpMap.x = IN.uv_BumpMap.x + _Speed * _Time;
// 对法线贴图进行采样
fixed3 nor = UnpackNormal (tex2D(_BumpMap, IN.uv_BumpMap));
// 对主材质进行采样
fixed4 tex = tex2D(_MainTex, IN.uv_MainTex);
// 【将反射的图像正常显示在此对象上】
// 获取屏幕纹理坐标信息
float2 screenUV = IN.screenPos.xy / IN.screenPos.w;
// 针对法线纹理做法线扭曲，_Distortion为扭曲强度
screenUV += nor.xy * _Distortion ;
// 对反射纹理进行采样，通过屏幕纹理
fixed4 ref = tex2D(_Ref, screenUV);
// 【将屏幕的纹理正常显示在此对象上】，如果不需要半透明可去掉
// 获取顶点在屏幕的坐标为纹理
float4 screenUV2 = IN.screenPos;
// 以下是根据平台来判断是否需要倒置Y坐标
// D3D:scale=-1，那么screenUV2.y = -1 * screenUV2.y + screenUV2.w;【倒置后+w让值域保持为0到1】
// OpenGL:scale=1，那么screenUV2.y = screenUV2.y;
#if UNITY_UV_STARTS_AT_TOP
float scale = -1.0;
#else
float scale = 1.0;
#endif
screenUV2.y = (screenUV2.y - screenUV2.w * 0.5) * scale + screenUV2.w * 0.5;
screenUV2.xy = screenUV2.xy / screenUV2.w;
// 针对法线纹理做的法线扭曲,_Distortion为强度
screenUV2.xy += nor.xy * _Distortion;
// 对屏幕纹理进行采样
fixed4 trans = tex2D(_GrabTexture,screenUV2.xy);
// 最终颜色 = 主材质颜色 * 主颜色 * 主色显示强度
o.Albedo = tex.rgb * _Color.rgb * _BlendLevel;
// 反射颜色 = 反射材质颜色和【屏幕纹理颜色】的插值
o.Emission = lerp(ref.rgb,trans.rgb,_Transparency);
// 法线值 = 法线材质颜色 * 法线强度
o.Normal = nor.rgb * _Bumpness;
// 发光强度 = 主纹理A
o.Gloss = tex.a;
// 透明度 = 主色
o.Alpha = tex.a * _Color.a;
// 镜面高光【高光需要针对针对非立方体，如果是平面BlinnPhong也无效】
o.Specular = _Shininess * _SpecColor;
}
ENDCG
}//end subshader
}
镜子代码Mirror 如下：
using UnityEngine;
using System.Collections;
[ExecuteInEditMode]
public class Mirror : MonoBehaviour
{
public bool m_DisablePixelLights = true;
public int m_TextureSize = 256;
public float m_ClipPlaneOffset = 0.07f;
public bool m_IsFlatMirror = true;
public LayerMask m_ReflectLayers = -1;
private Hashtable m_ReflectionCameras = new Hashtable();
private RenderTexture m_ReflectionTexture = null;
private int m_OldReflectionTextureSize = 0;
private static bool s_InsideRendering = false;
public void OnWillRenderObject()
{
if( !enabled || !renderer || !renderer.sharedMaterial || !renderer.enabled )
return;
Camera cam = Camera.current;
if( !cam )
return;
if( s_InsideRendering )
return;
s_InsideRendering = true;
Camera reflectionCamera;
CreateMirrorObjects( cam, out reflectionCamera );
Vector3 pos = transform.position;
Vector3 normal;
if(m_IsFlatMirror){
normal = transform.up;
}
else{
normal= transform.position - cam.transform.position ;
normal.Normalize();
}
int oldPixelLightCount = QualitySettings.pixelLightCount;
if( m_DisablePixelLights )
QualitySettings.pixelLightCount = 0;
UpdateCameraModes( cam, reflectionCamera );
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;
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;
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("_Ref") )
mat.SetTexture( "_Ref", m_ReflectionTexture );
}
if( m_DisablePixelLights )
QualitySettings.pixelLightCount = oldPixelLightCount;
s_InsideRendering = false;
}
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;
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;
}
}
dest.farClipPlane = src.farClipPlane;
dest.nearClipPlane = src.nearClipPlane;
dest.orthographic = src.orthographic;
dest.fieldOfView = src.fieldOfView;
dest.aspect = src.aspect;
dest.orthographicSize = src.orthographicSize;
dest.renderingPath = src.renderingPath;
}
private void CreateMirrorObjects( Camera currentCamera, out Camera reflectionCamera )
{
reflectionCamera = null;
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;
}
reflectionCamera = m_ReflectionCameras[currentCamera] as Camera;
if( !reflectionCamera )
{
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;
}
}
private static float sgn(float a)
{
if (a > 0.0f) return 1.0f;
if (a < 0.0f) return -1.0f;
return 0.0f;
}
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) );
}
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)));
projection[2] = c.x - projection[3];
projection[6] = c.y - projection[7];
projection[10] = c.z - projection[11];
projection[14] = c.w - projection[15];
}
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;
}
}
转自：http://blog.sina.com.cn/s/blog_89d90b7c0102vgk1.html
