Unity Shader案例篇-镜子（一）
发表于2018-06-12
本篇文章和大家介绍下使用shader实现镜子效果，先上效果图：
其中使用的Unity版本是在5.3.3。
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
Shader "Custom/Cg shader for virtual objects in mirrors" ｛
Properties｛
_Color("Virtual Object's Color", Color) = (1, 1, 1, 1)
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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;
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struct vertexOutput ｛
float4 pos : SV_POSITION;
float4 posInMirror : TEXCOORD0;
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vertexOutput vert(vertexInput input)
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vertexOutput output;
output.posInMirror = mul(_WorldToMirror,
mul(_Object2World, input.vertex));
output.pos = mul(UNITY_MATRIX_MVP, input.vertex);
return output;
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float4 frag(vertexOutput input) : COLOR
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//如果镜子里的物体出来了就剔除掉
if (input.posInMirror.y > 0.0)
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discard;
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return float4(_Color.rgb, 0.0);
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ENDCG
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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
Shader "Unlit/Cg shader for Real objects"
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Properties｛
_Color("Virtual Object's Color", Color) = (1, 1, 1, 1)
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SubShader ｛
Pass ｛
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
uniform float4 _Color;
float4 vert(float4 vertexPos : POSITION) : SV_POSITION
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return mul(UNITY_MATRIX_MVP, vertexPos);
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float4 frag(void) : COLOR
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return float4(_Color.rgb, 1.0);
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ENDCG
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4、建立一个镜子的材质并将下面的Shader代码赋给作为镜子的那个面板
Shader "Unlit/Mirrors"
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Properties｛
_Color("Mirrors's Color", Color) = (1, 1, 1, 1)
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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
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return mul(UNITY_MATRIX_MVP, vertexPos);
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float4 frag(void) : COLOR
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return float4(1.0, 0.0, 0.0, 0.0);
// this color should never be visible,
// only alpha is important
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ENDCG
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// 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
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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;
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float4 frag(void) : COLOR
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return float4(_Color.rgb, 0.0);
// set alpha to 0.0 and
// the color to the user-specified background color
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ENDCG
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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
using UnityEngine;
using System.Collections;
[ExecuteInEditMode]
public class PlacingTheVirtualObj : MonoBehaviour ｛
public GameObject objectInFrontOfMirror;
public GameObject mirrorPlane;
// Use this for initialization
void Start () ｛
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// Update is called once per frame
void Update() ｛
if (null != mirrorPlane)
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//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)
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//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);
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