Unity Shader实现3D翻页效果

Shader "Unlit/PaperTurnMilkShader"
{
 Properties
 {
  //正面图
  _MainTex ("Texture", 2D) = "white" {}
  //背面图
  _SrcTex("SrcTex", 2D) = "white"{}
  //旋转角度
  _Angle("Angle", Range(0,180)) = 0
  //弯曲程度
  _WeightY("Weight Y", Range(0,3)) = 0.2
  //收缩程度（值越大翻页时纸张越往内部靠拢)具体情况可测试
  _WeightX("Weight X", Range(0,1)) = 0
  //波长（值越大翻页时的弯曲次数越多）
  _WaveLength("WaveLength", Range(0,2)) = 0.4
 }
 SubShader
 {
  //关闭批处理（因为修改了顶点位置)
  Tags { "RenderType"="Opaque" "IgnoreProjector" = "True" "Queue" = "Geometry" "DisableBatching" = "True"}
  LOD 100
  //渲染正面
  Pass
  {
   Cull Back
   CGPROGRAM
   #pragma vertex vert
   #pragma fragment frag   
   
   #include "UnityCG.cginc"
 
   struct appdata
   {
    float4 vertex : POSITioN;
    float2 uv : TEXCOORD0;
   };
 
   struct v2f
   {
    float2 uv : TEXCOORD0;    
    float4 vertex : SV_POSITION;
   };
 
   sampler2D _MainTex;
   float4 _MainTex_ST;
   float _Angle;
   float _WeightY;
   float _WeightX;
   float _WaveLength;
   
   v2f vert (appdata v)
   {
    v2f o;
    //对顶点进行往X正方向偏移5个单位是为了离开旋转中心点,不然翻页时的旋转点是会在纸张中心进行围绕Z轴旋转（Z轴是纸张垂直线）
    v.vertex += float4(5, 0, 0, 0);
    float s;
    float c;
    //使用sincos获取 sin(弧度), cos(弧度)  ，radians(角度)=弧度 ,_Angle前加负号是控制旋转方向，可根据DX是右手法则顺时针旋转，故应该逆向翻页要取负数
    sincos(radians(-_Angle), s, c);
    //围绕Z轴旋转变换矩阵
    float4x4 rotate = {
     c,s,0,0,
     -s,c,0,0,
     0,0,1,0,
     0,0,0,1
    };
    //weight：_Angle在[0,90]变换区间时，weight会从0变为1；_Angle在[90,180]变换区间时，weight会从1变为0. 
    //weight可理解为是刚开始翻页（0°）到翻页到垂直时（90°）时，对其弯曲程度从小变大；（这个是对顶点Y值影响的结果）
    //同理，收缩程度也是一样道理
    float weight = 1 - abs(90 - _Angle) / 90;
    v.vertex.y += sin(v.vertex.x * _WaveLength) * weight * _WeightY;
    v.vertex.x -= v.vertex.x * weight * _WeightX;
    //在进行偏移之后，再对顶点进行围绕Z轴旋转_Angle角度
    v.vertex = mul(rotate, v.vertex);
 
    //之后要偏移回来，因为我们已经做完了上面的旋转操作了
    v.vertex -= float4(5, 0, 0, 0);
    o.vertex = UnityObjectToClipPos(v.vertex);
    o.uv = TRANSFORM_TEX(v.uv, _MainTex);    
    return o;
   }
   
   fixed4 frag (v2f i) : SV_Target
   {    
    fixed4 col = tex2D(_MainTex, i.uv);    
    return col;
   }
   ENDCG
  }
 
  //渲染背面(和上方渲染正面PASS唯一的差别是：片元着色器的采样纹理改为_SrcTex(背面图）
  Pass
  {
   Cull Front
   CGPROGRAM
   #pragma vertex vert
   #pragma fragment frag   
 
   #include "UnityCG.cginc"
 
   struct appdata
   {
    float4 vertex : POSITION;
    float2 uv : TEXCOORD0;
   };
 
   struct v2f
   {
    float2 uv : TEXCOORD0;
    float4 vertex : SV_POSITION;
   };
 
   sampler2D _SrcTex;
   float4 _MainTex_ST;
   float _Angle;
   float _WeightY;
   float _WeightX;
   float _WaveLength;
   v2f vert(appdata v)
   {
    v2f o;
    v.vertex += float4(5, 0, 0, 0);
    float s;
    float c;
    //使用sincos获取 sin(弧度), cos(弧度)  ，radians(角度)=弧度
    sincos(radians(-_Angle), s, c);
    //围绕Z轴旋转变换矩阵
    float4x4 rotate = {
     c,s,0,0,
     -s,c,0,0,
     0,0,1,0,
     0,0,0,1
    };
    float weight = 1 - abs(90 - _Angle) / 90;
    v.vertex.y += sin(v.vertex.x * _WaveLength) * weight * _WeightY;
    v.vertex.x -= v.vertex.x * weight * _WeightX;
    v.vertex = mul(rotate, v.vertex);
 
    v.vertex -= float4(5, 0, 0, 0);
 
    o.vertex = UnityObjectToClipPos(v.vertex);
    o.uv = TRANSFORM_TEX(v.uv, _MainTex);
    return o;
   }
 
   fixed4 frag(v2f i) : SV_Target
   {
    fixed4 col = tex2D(_SrcTex, i.uv);
    return col;
   }
   ENDCG
  }
 }
}