Shader案例篇—《镜子1》

    废话不多说先上效果图，我使用的是在.3.3版本。

Mirror.gif

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一、原理

1、首先要准备的素材是三个，对没错，就是三个因为镜子里面的那个物体其实是实物的复制体而已；一个Plane作为镜子，还有一个实物和虚物体。

2、新建一个材质使用下面的Shader代码，并将此材质球赋给那个虚物体

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Shader "Custom/Cg shader for virtual objects in mirrors" {          Properties{                  _Color( "Virtual Object's Color" , Color) = (1, 1, 1, 1)          }                  SubShader{                  Tags{ "Queue" = "Transparent+20" }                    Pass{                  Blend OneMinusDstAlpha DstAlpha                    CGPROGRAM   #pragma vertex vert #pragma fragment frag   #include "UnityCG.cginc"                    uniform float4 _Color;          uniform float4x4 _WorldToMirror;            struct vertexInput {                  float4 vertex : POSITION;          };          struct vertexOutput {                  float4 pos : SV_POSITION;                  float4 posInMirror : TEXCOORD0;          };            vertexOutput vert(vertexInput input)          {                  vertexOutput output;                    output.posInMirror = mul(_WorldToMirror,                          mul(_Object2World, input.vertex));                  output.pos = mul(UNITY_MATRIX_MVP, input.vertex);                  return output;          }            float4 frag(vertexOutput input) : COLOR          {                  //如果镜子里的物体出来了就剔除掉                  if (input.posInMirror.y > 0.0)                  {                          discard;                  }          return float4(_Color.rgb, 0.0);          }                    ENDCG          }          } }

3、另外在建一个材质使用下面的Shader代码，并将此材质球赋值给实物体

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Shader "Unlit/Cg shader for Real objects" {          Properties{                  _Color( "Virtual Object's Color" , Color) = (1, 1, 1, 1)          }     SubShader {        Pass {           CGPROGRAM             #pragma vertex vert           #pragma fragment frag                  uniform float4 _Color;           float4 vert(float4 vertexPos : POSITION) : SV_POSITION           {              return mul(UNITY_MATRIX_MVP, vertexPos);           }             float4 frag( void ) : COLOR           {              return float4(_Color.rgb, 1.0);           }             ENDCG        }     } }

4、在建一个材质使用下面的Shader代码，并将这个材质赋值给作为镜子的面板

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Shader "Unlit/Mirrors" {          Properties{                  _Color( "Mirrors's Color" , Color) = (1, 1, 1, 1)          }                  SubShader{                  Tags{ "Queue" = "Transparent+10" }                  // draw after all other geometry has been drawn                  // because we mess with the depth buffer                  //确保在所有的真实物体渲染之后再渲染                    // 1st pass: mark mirror with alpha = 0                  Pass{                  CGPROGRAM   #pragma vertex vert #pragma fragment frag                    float4 vert(float4 vertexPos : POSITION) : SV_POSITION          {                  return mul(UNITY_MATRIX_MVP, vertexPos);          }                    float4 frag( void ) : COLOR          {                  return float4(1.0, 0.0, 0.0, 0.0);          // this color should never be visible,          // only alpha is important          }                  ENDCG          }                    // 2nd pass: set depth to far plane such that                  // we can use the normal depth test for the reflected geometry                  Pass{                  ZTest Always                  Blend OneMinusDstAlpha DstAlpha                  //==float4 result = float4(1.0 - pixel_color.a) * fragment_output + float4(pixel_color.a) * pixel_color;                    CGPROGRAM   #pragma vertex vert #pragma fragment frag                    uniform float4 _Color;          // user-specified background color in the mirror            float4 vert(float4 vertexPos : POSITION) : SV_POSITION          {                  float4 pos = mul(UNITY_MATRIX_MVP, vertexPos);                  pos.z = pos.w;                  // the perspective division will divide pos.z                  // by pos.w; thus, the depth is 1.0,                  // which represents the far clipping plane                  return pos;          }                    float4 frag( void ) : COLOR          {                  return float4(_Color.rgb, 0.0);          // set alpha to 0.0 and          // the color to the user-specified background color          }                  ENDCG          }          } }

5、最后新建一个C#脚本，代码如下，将此代码赋给虚物体，并将Plane和虚物体拖动赋值给里面的对应两个变量

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using UnityEngine; using System.Collections;   [ExecuteInEditMode] public class PlacingTheVirtualObj : MonoBehaviour {        public GameObject objectInFrontOfMirror;      public GameObject mirrorPlane;        // Use this for initialization      void Start () {                    }        // Update is called once per frame      void Update() {          if ( null != mirrorPlane)          {              //这句话决定了镜子里的物体是否可见              GetComponent<Renderer>().sharedMaterial.SetMatrix( "_WorldToMirror" ,mirrorPlane.GetComponent<Renderer>().worldToLocalMatrix);              if ( null != objectInFrontOfMirror)              {                  //将实物的颜色值赋给镜中的物体                  Color realColor = objectInFrontOfMirror.GetComponent<Renderer>().material.GetColor( "_Color" );                  GetComponent<Renderer>().material.SetColor( "_Color" , realColor);                    transform.position = objectInFrontOfMirror.transform.position;                  transform.rotation = objectInFrontOfMirror.transform.rotation;                  transform.localScale =                     -objectInFrontOfMirror.transform.localScale;                  //new Vector3(0.0f, 1.0f, 0.0f)为表面的法线方向                  transform.RotateAround(objectInFrontOfMirror.transform.position,mirrorPlane.transform.TransformDirection( new Vector3(0.0f, 1.0f, 0.0f)), 180.0f);                Vector3  positionInMirrorSpace  =                     mirrorPlane.transform.InverseTransformPoint(objectInFrontOfMirror.transform.position);                  positionInMirrorSpace.y = -positionInMirrorSpace.y;                  transform.position = mirrorPlane.transform.TransformPoint(                     positionInMirrorSpace);              }          }      } }

二、此方案的优劣

1、优点：性能开销比较小，镜子里的虚物体清晰

2、缺点：目前虚物体只能实时的同步实物体的颜色，贴图和其他纹理或者模型面数复杂的情况都没有响应的处理、并不是完全的实时反射物体，因为要实现创建好虚物体。

3、有待发现…..

三、后续待….

原贴地址 蛮牛网凯尔八阿哥转载请注明出处

之前有童鞋没有实现出来，是我太粗心了，一激动少说了一个Shader脚本，就是第四个，现在已经添加进来了，还是附上最后的工程文件吧，方便大家学习和参考。

工程文件下载地址 https://pan.baidu.com/s/1o84hcdO