What is _ maintex_st?

【What is _ maintex_st?]

In Unity's built-in unbind/texture, float4 _ maintex_st is referenced as follows:

// Unlit shader. Simplest possible textured shader.// - no lighting// - no lightmap support// - no per-material colorShader "Unlit/Texture" {Properties {    _MainTex ("Base (RGB)", 2D) = "white" {}}SubShader {    Tags { "RenderType"="Opaque" }    LOD 100        Pass {          CGPROGRAM            #pragma vertex vert            #pragma fragment frag                        #include "UnityCG.cginc"            struct appdata_t {                float4 vertex : POSITION;                float2 texcoord : TEXCOORD0;            };            struct v2f {                float4 vertex : SV_POSITION;                half2 texcoord : TEXCOORD0;            };            sampler2D _MainTex;            float4 _MainTex_ST;                        v2f vert (appdata_t v)            {                v2f o;                o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);                o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);                return o;            }                        fixed4 frag (v2f i) : SV_Target            {                fixed4 col = tex2D(_MainTex, i.texcoord);                return col;            }        ENDCG    }}}

View code

Transform_tex macro:

　　

Indeed for any texture property, Unity provides value for float4 with "_ ST" suffix. the X, Y contains texture scale, and Z, W contains translation (offset ).

The _ st variable has four values, XY is texture scale, and ZW is offset.

　　

In material, tiling can be set to XY, and offset to ZW.

Reference: http://forum.unity3d.com/threads/what-is-_maintex_st.24962/

What is _ maintex_st?