Unity custom shaders and z-fighting
- by Heisenbug
I've just readed a chapter of Unity iOS Essential by Robert Wiebe.
It shows a solution for handling z-figthing problem occuring while rendering a street on a plane with the same y offset.
Basically it modified Normal-Diffuse shader provided by Unity, specifing the (texture?) offset in -1, -1.
Here's basically what the shader looks like:
Shader "Custom/ModifiedNormalDiffuse" {
Properties {
_Color ("Main Color", Color) = (1,1,1,1)
_MainTex ("Base (RGB)", 2D) = "white" {}
}
SubShader {
Offset -1,-1 //THIS IS THE ADDED LINE
Tags { "RenderType"="Opaque" }
LOD 200
CGPROGRAM
#pragma surface surf Lambert
sampler2D _MainTex;
fixed4 _Color;
struct Input {
float2 uv_MainTex;
};
void surf (Input IN, inout SurfaceOutput o) {
half4 c = tex2D (_MainTex, IN.uv_MainTex) *_Color;
o.Albedo = c.rgb;
o.Alpha = c.a;
}
ENDCG
}
FallBack "Diffuse"
}
Ok. That's simple and it works.
The author says about it:
...we could use a copy of the shader that draw the road at an Offset
of -1, -1 so that whenever the two textures are drawn, the road is
always drawn last.
I don't know CG nor GLSL, but I've a little bit of experience with HLSL. Anyway I can't figure out what exactly is going on.
Could anyone explain me what exactly Offset directly does, and how is solves z-fighting problems?
