ShaderLab 'if' statement

Graphics Shaders & Materials
1

In my shader I like to change the used UV channel. the condition does NOT change for the selected material so doing the if statement for very vertex for every frame is unnecessary.

_UVChannel ("UV Channel", Int) = 1

...

fixed2 uv        : TEXCOORD0;
fixed2 uv2    : TEXCOORD1;

...

if( _UVChannel == 1.0)
    uv = v.uv;
else
    uv = v.uv2;

o.uv = TRANSFORM_TEX(uv, _MainTex);

I could have created multiple shaders, but is there other solution?
Wondering can there be anything like:

Category {
  if (_UVChannel > 0)
    SubShader { ... }
  else {
    SubShader { ... }
  }
}

Unanswered 7 year old topic exists:
http://forum.unity3d.com/threads/shaderlab-if-statement.8904/

P.S can not reply the old thread because:
“(You have insufficient privileges to reply here.)”

2344766–158647–UnlitSelectTexture.shader (978 Bytes)

2

Yo can use #pragma multi_compile directive to create multiple shader variants and “KeywordEnum” property drawer to enable\disable keywords.

But be careful with keywords. There is a limit of 128 keywords in project.

1 Like
3

If it’s a material setting exposed in the material editor, it’s advised to use shader_feature instead of multi_compile.

So then it becomes something like:

#pragma shader_feature _ _USE_UV1_FOR_UV0

#ifdef _USE_UV1_FOR_UV0
fixed2 uv    : TEXCOORD1;
#else
fixed2 uv    : TEXCOORD0;
#endif

You’ll need to use a script to actually define or undefine the _USE_UV1_FOR_UV0 keyword.

4

In fact you don’t.

[Toggle(_USE_UV1_FOR_UV0)] _SwapUVs (“Swap UVs”, Float) = 1.0

http://docs.unity3d.com/ScriptReference/MaterialPropertyDrawer.html