shader not support more than two uv sets in mobile

Unity Engine
1

i write a shader use more than two uv sets. it works in editor and pc. but fails in mobile device, test on android and ios, both fail. i see BindChannels: maximum two uv sets? . I use 2017.2.0f3 .
Is this a bug or not support now?

struct v2f
{
fixed2 uv0 : TEXCOORD0;
fixed2 uv1 : TEXCOORD1;
fixed2 uv2 : TEXCOORD2;
fixed4 vertex : SV_POSITION;
};

sampler2D _MainTex;
sampler2D _AlphaTex;
fixed4 _MainTex_ST;

v2f vert(appdata v)
{
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv0 = TRANSFORM_TEX(v.uv, _MainTex);
o.uv1 = v.uv;
o.uv2 = v.uv;
return o;
}

fixed4 frag(v2f i) : SV_Target
{
// sample the texture
fixed4 col = tex2D(_MainTex, i.uv0);
col.a = tex2D(_AlphaTex, i.uv1).a;
col.a *= tex2D(_AlphaTex, i.uv2).a;
return col ;
}

2

What do you mean by fail? Is there a compilation error when you make the build? Does the object not render, or render pink, or just look funny?

If it just doesn’t look like you expect, but does render, it’s likely because you’re using fixed2 for the v2f UVs. The fixed variable type is defined as:

On desktop, GPUs just use either a full 32 bit or 16 bit float (the float and half variable types respectively, depending on the GPU) when you use fixed. Both of those variable types have significantly more precision and range than the fixed variable definition needs, but the definition just has a minimum range and precision, not maximum.

On mobile, a fixed variable may really be just that minimum range and precision implemented as an 11 bit float. So that means something that might work in the editor with fixed might not on a mobile device.

TLDR; You should use float2 or half2 instead of fixed2 for UVs. Similarly the SV_POSITION should always be a float4, as should the _MainTex_ST. The use of fixed variables should be limited to color values.

3

in mobile device，it is pink。 when compile bundle ，no error。 i check log use ADB， i not find erroe log

4

Post the entire shader then, and please use the [ code ] tag. And try changing the SV_Position to float4.