Morten Nobel's Blog

In Unity there is two settings of a texture UV mode: Repeat: simply repeat that the textures (usable for tileable texture images) and Clamp: clamps the UV coordinates to  a value between 0.0 and 1.0. In this blog I’ll show how to get a third option: Mirror: mirrors the texture whenever the UV crosses a integer number.

The three UV texture modes are:

Even though Unity’s texture import settings only has the repeat and clamp, it is very easy to get a mirror effect as well. All it takes is to create a new shader that mirrors the texture coordinates before looking up in the texture.

To create a mirror effect you can use the following cg-code:

// makes the UV repeat between 0.0 and 2.0
float2 t = frac(IN.uv_MainTex*0.5)*2.0; 
float2 length = {1.0,1.0};
// compute the mirror effect
float2 mirrorTexCoords = length-abs(t-length); 

I have created a diffuse shader with the mirrored UV coordinates (it is based on “Normal-Diffuse.shader” from Builtin Unity Shaders):

Shader "Custom/DiffuseUVMirrowShader" {
Properties {
	_Color ("Main Color", Color) = (1,1,1,1)
	_MainTex ("Base (RGB)", 2D) = "white" {}
}
SubShader {
	Tags { "RenderType"="Opaque" }
	LOD 200

CGPROGRAM
#pragma surface surf Lambert

sampler2D _MainTex;
float4 _Color;

struct Input {
	float2 uv_MainTex;
};

void surf (Input IN, inout SurfaceOutput o) {
	// makes the UV repeat between 0.0 and 2.0
	float2 t = frac(IN.uv_MainTex*0.5)*2.0; 
	float2 length = {1.0,1.0};
	float2 mirrorTexCoords = length-abs(t-length); 
	// compute the mirror effect
	half4 c = tex2D(_MainTex,  mirrorTexCoords) * _Color;
	o.Albedo = c.rgb;
	o.Alpha = c.a;
}
ENDCG
}

Fallback "VertexLit"
}