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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
}
}
}
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