// Packs the metallic-smoothness WORK layout into the URP _MetallicGlossMap layout.
//
// While painting, the metallic-smoothness map is kept in a "work" RenderTexture as
//   R = metallic, G = smoothness, A = coverage (painted marker for the dilation pass).
// This lets the same brush + dilate shaders (which use alpha as the coverage marker)
// drive it exactly like the albedo map. But URP's _MetallicGlossMap expects
//   R = metallic, A = smoothness.
// This pass converts work -> final after each stroke: out = (work.r, 0, 0, work.g).
//
// Both work and final are linear RenderTextures (metallic/smoothness are data, not
// color), so no gamma conversion happens.
Shader "Hidden/MeshPaintPackMS"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType" = "Opaque" }
        Pass
        {
            ZTest Always
            ZWrite Off
            Cull Off
            Blend Off

            CGPROGRAM
            #pragma vertex vert_img
            #pragma fragment frag
            #include "UnityCG.cginc"

            sampler2D _MainTex;

            fixed4 frag (v2f_img i) : SV_Target
            {
                fixed4 c = tex2D(_MainTex, i.uv);
                return fixed4(c.r, 0.0, 0.0, c.g); // R = metallic, A = smoothness
            }
            ENDCG
        }
    }
    Fallback Off
}