Accessing uv offset in Cg shader

Questions & Answers
1

How does one access the "Tiling" and "Offset" values set on a Texture in a Cg shader? I assume it's set somewhere, but I can't find documentation about it.

3

Inside the UnityCG.cginc, you will find a macro:

// Transforms 2D UV by scale/bias property
#define TRANSFORM_TEX(tex,name) (tex.xy * name##_ST.xy + name##_ST.zw)

Where the first parameter is the texcoord and the second parameter is the texture:

Example:

TRANSFORM_TEX(v.texcoord, _MainTex);
5

I’ve made an example, there are two lines that are of interest, Ive marked them with “LOOK”

 //Flat color texture, does not support alpha channels
    Shader "Viking/FlatAdv"
    {
    	Properties
    	{
    		_MainTex ( "Main Texture", 2D ) = "white" {}
    	}
    	
    	SubShader
    	{
    		Tags { "Queue" = "Geometry" }
    		ZWrite On
    		Blend SrcAlpha OneMinusSrcAlpha
    		
    		Pass
    		{
    CGPROGRAM
    #pragma exclude_renderers ps3 xbox360 flash
    #pragma fragmentoption ARB_precision_hint_fastest
    #pragma vertex vert
    #pragma fragment frag
    
    #include "UnityCG.cginc"
    
    
    // uniforms
    uniform sampler2D _MainTex;
    //LOOK! The texture name + ST is needed to get the tiling/offset
    uniform float4 _MainTex_ST; 
    
    
    struct vertexInput
    {
    	float4 vertex : POSITION; 
    	float4 texcoord : TEXCOORD0;
    };
    
    
    struct fragmentInput
    {
    	float4 pos : SV_POSITION;
    	half2 uv : TEXCOORD0;
    };
    
    
    fragmentInput vert( vertexInput i )
    {
    	fragmentInput o;
    	o.pos = mul( UNITY_MATRIX_MVP, i.vertex );

//This is a standard defined function in Unity, 
//Does exactly the same as the next line of code
    	//o.uv = TRANSFORM_TEX( i.texcoord, _MainTex );
    
//LOOK! _MainTex_ST.xy is tiling and _MainTex_ST.zw is offset
        o.uv =  i.texcoord.xy * _MainTex_ST.xy + _MainTex_ST.zw;
    
    	return o;
    }
    
    
    half4 frag( fragmentInput i ) : COLOR
    {
    	return half4( tex2D( _MainTex, i.uv ).rgb, 1.0);
    }
    
    ENDCG
    		} // end Pass
    	} // end SubShader
    	
    	FallBack "Diffuse"
    }
4

Hi, I think this will be to late for an answer but if you are interested you can try this:

// this is the main form to access the tile (scale) and offset in a texture property.
renderer.material.SetTextureOffset("_MainTex", Vector2(.25,.15));
renderer.material.SetTextureScale("_MainTex", Vector2(2,3));

This use the properties in the shader no matter it’s a CG or not, with you can manipulate it using a simple script, you can check this to see how it’s applied. ;-), the previous answer is to use it inside the shader.

2

This is a bit old, I guess, but if you’re still looking, there’s some information in:
http://unity3d.com/support/documentation/Manual/ShaderTut2.html

There’s a function in UnityCG.cginc that handles the offset and scaling, so going through that would be a good place to start.