Unity Shader学习随笔

 Pass
{
    CGPROGRAM
    #pragma vertex vert
    #pragma fragment frag

    #include "UnityCG.cginc"

    struct v2f
    {
        float2 uv : TEXCOORD0;
    };

    sampler2D _GrabTex;
    sampler2D _MainTex;float4 _MainTex_ST;
    fixed _SpeedX, _SpeedY, _Distort;

    v2f vert (float4 vertex : POSITION, float2 uv : TEXCOORD0, out float4 pos : SV_POSITION)
    {
        pos = UnityObjectToClipPos(vertex);
        v2f o;
        o.uv = TRANSFORM_TEX(uv, _MainTex) + float2(_SpeedX, _SpeedY) * _Time.x;
        return o;
    }
    //由于VPOS和SV_POSITION冲突，因此需要在vert里out
    fixed4 frag (v2f i, UNITY_VPOS_TYPE screenPos:VPOS) : SV_Target
    {
        //最初的版本，通过unity参数去计算，_ScreenParams.xy是屏幕的宽高
        fixed2 uv = lerp(screenPos.xy / _ScreenParams.xy, tex2D(_MainTex, i.uv).xy, _Distort);
        fixed4 grabTex = tex2D(_GrabTex, uv);
        return grabTex;
    }
    ENDCG
}

 Pass
{
    CGPROGRAM
    #pragma vertex vert
    #pragma fragment frag

    #include "UnityCG.cginc"

    struct a2f
    {
        float4 vertex : POSITION;
        float2 uv : TEXCOORD0;
    };

    struct v2f
    {
        float2 uv : TEXCOORD0;
        float4 pos : SV_POSITION;
        float2 screenUV : TEXCOORD1;
    };

    sampler2D _GrabTex;
    sampler2D _MainTex;float4 _MainTex_ST;
    fixed _SpeedX, _SpeedY, _Distort;

    v2f vert (a2f v)
    {
        v2f o;
        o.uv = TRANSFORM_TEX(v.uv, _MainTex) + float2(_SpeedX, _SpeedY) * _Time.x;
        o.pos = UnityObjectToClipPos(v.vertex);
        //1.此时pos是放在正交矩形中的顶点
        //2.因此可以直接拿该值当做屏幕坐标
        //3.但要注意pos的范围是-1到1
        //4.因此需要把它规范到0到1，但OpenGL和DX11的屏幕坐标原点不同
        //5.OpenGL的在左下角，仅需将xy * 0.5 + 0.5即可
        //6.但DX11的在左上角，需要将y轴反转，即y = 1 - y
        // o.screenUV = o.pos.xy / o.pos.w * 0.5 + 0.5;
        // o.screenUV.y = 1 - o.screenUV.y;
        //7.上面就是根据正交中的顶点坐标转换成屏幕坐标的操作
        //8.可以注意到稍微有点扭曲，原因是顶点不是片元，顶点和顶点之间的参数都是靠插值算出来的
        // o.screenUV = ComputeScreenPos(o.pos) / o.pos.w;
        //9.当然，unitycg提供了方法，上面
        //10.这里除以一个w是因为：正交矩形中是正交的，而相机是透视的，要将其还原
        return o;
    }

    fixed4 frag (v2f i) : SV_Target
    {
        fixed2 uv = lerp(i.screenUV, tex2D(_MainTex, i.uv).xy, _Distort);
        fixed4 grabTex = tex2D(_GrabTex, uv);
        return grabTex;
    }
    ENDCG
}

 Pass
{
    CGPROGRAM
    #pragma vertex vert
    #pragma fragment frag

    #include "UnityCG.cginc"

    struct a2f
    {
        float4 vertex : POSITION;
        float2 uv : TEXCOORD0;
    };

    struct v2f
    {
        float2 uv : TEXCOORD0;
        float4 pos : SV_POSITION;
        float2 screenUV : TEXCOORD1;
    };

    sampler2D _GrabTex;
    sampler2D _MainTex;float4 _MainTex_ST;
    fixed _SpeedX, _SpeedY, _Distort;

    v2f vert (a2f v)
    {
        v2f o;
        o.uv = TRANSFORM_TEX(v.uv, _MainTex) + float2(_SpeedX, _SpeedY) * _Time.x;
        o.pos = UnityObjectToClipPos(v.vertex);
        o.screenUV = o.pos;
        return o;
    }

    fixed4 frag (v2f i) : SV_Target
    {
        // return i.screenUV.x;
        // return i.pos.x;
        //可以看到，我明明对screenUV赋了pos的值，但上面两个居然不一样
        //那是因为SV_POSITION在中间经过了改变
        //在经过计算后,pos就是屏幕像素大小了,不再是-1到1了,那这样就更方便了;
        i.screenUV = i.pos.xy / _ScreenParams.xy;
        //OK，就上面这一行就解决战斗了
        fixed2 uv = lerp(i.screenUV, tex2D(_MainTex, i.uv).xy, _Distort);
        fixed4 grabTex = tex2D(_GrabTex, uv);
        return grabTex;
    }
    ENDCG
}