// Packs the mask-map WORK layout into the URP mask-map layout.
//
// While painting, the mask map is kept in a "work" RenderTexture as
//   R = metallic, G = smoothness, B = occlusion, A = coverage (painted marker for dilation).
// This lets the same brush + dilate shaders (which use alpha as the coverage marker)
// drive it exactly like the albedo map. The packed result is one texture bound to BOTH
//   _MetallicGlossMap (URP reads R = metallic, A = smoothness) and
//   _OcclusionMap     (URP reads G = occlusion).
// This pass converts work -> final after each stroke: out = (work.r, work.b, 0, work.g)
//   = (metallic, occlusion, 0, smoothness).
//
// Both work and final are linear RenderTextures (these 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);
                // work (R=metallic, G=smoothness, B=occlusion) -> (metallic, occlusion, 0, smoothness)
                return fixed4(c.r, c.b, 0.0, c.g);
            }
            ENDCG
        }
    }
    Fallback Off
}