_MainTex_ST表示

纹理偏移和缩放

S是Scale的首字母对应tiling, T是Translation的首字母对应Offset

  

Shader "My/Unlit"
{
    Properties
    {
        _MainTex("Main Tex", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType" = "Opaque" }

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 texcoord : TEXCOORD0;
            };

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

            sampler2D _MainTex;
            float4 _MainTex_ST;

            v2f vert(appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
                return o;
            }

            fixed4 frag(v2f i) : SV_Target
            {
                fixed4 c = tex2D(_MainTex, i.uv);
                return c;
            }

            ENDCG
        }
    } //SubShader
}

 

TRANSFORM_TEX宏

#define TRANSFORM_TEX(tex,name) (tex.xy * name##_ST.xy + name##_ST.zw)

o.uv = TRANSFORM_TEX(v.texcoord, _MainTex); 其实就相当于v.texcoord.xy * _MainTex_ST.xy + _MainTex_ST.zw

1) _MainTex_ST.xy对应Tiling的xy值

2) _MainTex_ST.zw对应Offset的xy值

 

参考

UnityShader精要笔记六 基础纹理 - 简书 (jianshu.com)