Shader "Hidden/ProBuilder/LineBillboard"
{
    Properties
    {
        _Color ("Color", Color) = (1,1,1,1)
        _Scale ("Scale", Range(0, 20)) = 7
        _HandleZTest ("_HandleZTest", Int) = 8
        _HandleZWrite("_HandleZWrite", Int) = 0
    }

    SubShader
    {
        Tags
        {
            "ProBuilderPicker"="EdgePass"
            "RenderType"="Geometry"
            "Queue"="Geometry"
            "DisableBatching"="True"
            "ForceNoShadowCasting"="True"
            "IgnoreProjector"="True"
        }

        Lighting Off
        ZTest [_HandleZTest]
        ZWrite [_HandleZWrite]
        Cull Off
        Blend Off
        Offset -1, -1

        Pass
        {
            Name "EdgePass"

            CGPROGRAM
            #pragma target 4.0
            #pragma vertex vert
            #pragma geometry geo
            #pragma fragment frag
            #pragma exclude_renderers metal
            #include "UnityCG.cginc"
            #include "ProBuilderCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                fixed4 color : COLOR;
            };

            struct v2f
            {
                float4 pos : SV_POSITION;
                fixed4 color : COLOR;
            };

            float _Scale;
            float4 _Color;

            v2f vert (appdata v)
            {
                v2f o;

                o.pos = float4(UnityObjectToViewPos(v.vertex.xyz), 1);

                // pull closer to camera and into clip space
                o.pos *= .99;
                o.pos = mul(UNITY_MATRIX_P, o.pos);
                // convert clip -> ndc -> screen, build billboards in geo shader, then screen -> ndc -> clip
                o.pos = ClipToScreen(o.pos);
                o.color = v.color;
                return o;
            }

            [maxvertexcount(4)]
            void geo(line v2f p[2], inout TriangleStream<v2f> triStream)
            {
                float2 perp = normalize(float2(-(p[1].pos.y - p[0].pos.y), p[1].pos.x - p[0].pos.x)) * _Scale;

                v2f geo_out;

                geo_out.pos = ScreenToClip( float4(p[1].pos.x + perp.x, p[1].pos.y + perp.y, p[1].pos.z, p[1].pos.w) );
                geo_out.color = p[1].color;
                triStream.Append(geo_out);

                geo_out.pos =  ScreenToClip( float4(p[1].pos.x - perp.x, p[1].pos.y - perp.y, p[1].pos.z, p[1].pos.w) );
                geo_out.color = p[1].color;
                triStream.Append(geo_out);

                geo_out.pos =  ScreenToClip( float4(p[0].pos.x + perp.x, p[0].pos.y + perp.y, p[0].pos.z, p[0].pos.w) );
                geo_out.color = p[0].color;
                triStream.Append(geo_out);

                geo_out.pos =  ScreenToClip( float4(p[0].pos.x - perp.x, p[0].pos.y - perp.y, p[0].pos.z, p[0].pos.w) );
                geo_out.color = p[0].color;
                triStream.Append(geo_out);
            }

            fixed4 frag (v2f i) : COLOR
            {
                return i.color * _Color;
            }

            ENDCG
        }
    }

    Fallback Off
}