Shader "VRCBoard/VRCBoardAtlasShader"
{
    Properties
    {
        // _MainTex
        _MainTexAtlas("Albedo", 2D) = "white" {}
        [HideInInspector] _MainTexAtlasSize("Atlas Size", int) = 1
        [HideInInspector] _MainTexAtlasIndex("Atlas Position", int) = 0
        [HideInInspector] _MainTexColor("Color", Color) = (1,1,1,1)

        // _EmissionMap
        _EmissionMapAtlas("Emission", 2D) = "black" {}
        [HideInInspector] _EmissionMapAtlasSize("Emission Atlas Size", int) = 1
        [HideInInspector] _EmissionMapAtlasIndex("Emission Atlas Position", int) = 0
        [HideInInspector] _EmissionColor("Emission Color", Color) = (1,1,1,1)

        // _NormalMap
        _NormalMapAtlas("Normal", 2D) = "bump" {}
        [HideInInspector] _NormalMapAtlasSize("Normal Atlas Size", int) = 1
        [HideInInspector] _NormalMapAtlasIndex("Normal Atlas Position", int) = 0
        [HideInInspector] _NormalMapScale("Normal Scale", float) = 1

    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 200

        CGPROGRAM
        #pragma surface surf Standard fullforwardshadows

        #pragma target 3.0

        sampler2D _MainTexAtlas;
        sampler2D _EmissionMapAtlas;
        sampler2D _NormalMapAtlas;

        uint _MainTexAtlasSize;
        uint _MainTexAtlasIndex;
        float4 _MainTexColor;


        uint _EmissionMapAtlasSize;
        uint _EmissionMapAtlasIndex;
        float4 _EmissionColor;

        uint _NormalMapAtlasSize;
        uint _NormalMapAtlasIndex;
        float _NormalMapScale;

        struct Input
        {
            float2 uv_MainTexAtlas;
            float2 uv_EmissionMapAtlas;
            float2 uv_NormalMapAtlas;
        };

        // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
        // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
        // #pragma instancing_options assumeuniformscaling
        UNITY_INSTANCING_BUFFER_START(Props)
        UNITY_INSTANCING_BUFFER_END(Props)

        void surf (Input IN, inout SurfaceOutputStandard o)
        {
            _MainTexAtlasIndex = _MainTexAtlasIndex+_MainTexAtlasSize;
            _EmissionMapAtlasIndex = _EmissionMapAtlasIndex+_EmissionMapAtlasSize;
            _NormalMapAtlasIndex = _NormalMapAtlasIndex+_NormalMapAtlasSize;

            float2 MainTexAtlasUV = float2(
                (float(_MainTexAtlasIndex % _MainTexAtlasSize) + IN.uv_MainTexAtlas.x) / _MainTexAtlasSize,
                1.0 - (float(_MainTexAtlasIndex / _MainTexAtlasSize) - IN.uv_MainTexAtlas.y) / _MainTexAtlasSize
            );

            float2 EmissionMapAtlasUV = float2(
                (float(_EmissionMapAtlasIndex % _EmissionMapAtlasSize) + IN.uv_EmissionMapAtlas.x) / _EmissionMapAtlasSize,
                1.0 - (float(_EmissionMapAtlasIndex / _EmissionMapAtlasSize) - IN.uv_EmissionMapAtlas.y) / _EmissionMapAtlasSize
            );

            float2 NormalMapAtlasUV = float2(
                (float(_NormalMapAtlasIndex % _NormalMapAtlasSize) + IN.uv_NormalMapAtlas.x) / _NormalMapAtlasSize,
                1.0 - (float(_NormalMapAtlasIndex / _NormalMapAtlasSize) - IN.uv_NormalMapAtlas.y) / _NormalMapAtlasSize
            );

            
            fixed4 c = tex2D (_MainTexAtlas, MainTexAtlasUV);
            fixed4 e = tex2D (_EmissionMapAtlas, EmissionMapAtlasUV);
            fixed4 n = tex2D (_NormalMapAtlas, NormalMapAtlasUV);
            
            o.Albedo = c.rgb * _MainTexColor.rgb;
            o.Emission = e.rgb * _EmissionColor.rgb;
            o.Normal = UnpackNormal(n);
        }
        ENDCG
    }
    FallBack "Diffuse"
    CustomEditor "VRCBoard.VRCBoardShaderEditor"
}