Shader "DBV/Kristo/UnlitClip"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Color ("Main color", Color) = (1,1,1,1)
        _BackFaceColor ("Inside color", Color) = (1,1,1,1)
        _FadeColor ("Rim color", Color) = (1,1,1,1) 
        _FadeDistance ("Fade distance", Float) = 10
        _FadeSmooth ("Fade smooth distance", Float) = 1

        _DitherTex ("Texture", 2D) = "grey" {}
    }
    SubShader {
        Tags { 
            "RenderType"="Opaque" 
            }
        LOD 100

        Pass {
            Cull Back
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            
            #pragma multi_compile_fog// make fog work

            #include "UnityCG.cginc"

            struct appdata {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                float4 screenPos : TEXCOORD1;
                };

            struct v2f {
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
                float4 worldSpace : TEXCOORD1;
                float4 screenPos : TEXCOORD2;
                };

            sampler2D _MainTex, _DitherTex;
            float4 _DitherTex_TexelSize;
            float4 _MainTex_ST;

            float4 _FadeColor, _BackFaceColor, _Color;
            float _FadeDistance, _FadeSmooth;

            v2f vert (appdata v) {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.worldSpace = mul(unity_ObjectToWorld, v.vertex);
                o.screenPos = ComputeScreenPos(o.vertex);
                UNITY_TRANSFER_FOG(o,o.vertex);
                return o;
                }

            fixed4 frag (v2f i) : SV_Target {
                // sample the texture
                fixed4 col = tex2D(_MainTex, i.uv) * _Color;
                fixed3 vec = i.worldSpace.xyz - _WorldSpaceCameraPos;
                float dis = vec.x*vec.x + vec.y*vec.y + vec.z*vec.z;

                float fadeDis = _FadeDistance * _FadeDistance;
                float fade = _FadeSmooth * _FadeSmooth;
                float fadeSmooth = fadeDis + fade;

                if(dis < fadeDis) {
                    col = 0;
                    clip(-1);
                    }
                else if (dis < fadeSmooth) {
                    float v = (1-(fadeSmooth-dis)/fade);
                    //Do dither fade
                    //https://www.ronja-tutorials.com/2019/05/11/dithering.html
                    float2 screenPos = i.screenPos.xy / i.screenPos.w;
                    float2 ditherCoordinate = screenPos * _ScreenParams.xy * _DitherTex_TexelSize.xy;
                    float ditherValue = tex2D(_DitherTex, ditherCoordinate).r;
                    clip(v - ditherValue);
                    col = col * v + (1-v) * _FadeColor;
                    }
                else{
                    //col.rgb *= i.worldSpace.xyz;
                    }
                
                // apply fog
                UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
                }
            ENDCG
            }

        Pass {
            Cull Front
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            
            #pragma multi_compile_fog// make fog work

            #include "UnityCG.cginc"

            struct appdata {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                float4 screenPos : TEXCOORD1;
                };

            struct v2f {
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
                float4 worldSpace : TEXCOORD1;
                float4 screenPos : TEXCOORD2;
                };

            float4 _BackFaceColor;
            float _FadeDistance, _FadeSmooth;

            sampler2D _DitherTex;
            float4 _DitherTex_TexelSize;

            v2f vert (appdata v) {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.worldSpace = mul(unity_ObjectToWorld, v.vertex);
                return o;
                }

            fixed4 frag (v2f i) : SV_Target {
                fixed3 vec = i.worldSpace.xyz - _WorldSpaceCameraPos;
                float dis = vec.x*vec.x + vec.y*vec.y + vec.z*vec.z;

                float fadeDis = _FadeDistance * _FadeDistance;
                float fade = _FadeSmooth * _FadeSmooth;
                float fadeSmooth = fadeDis + fade;

                if(dis < fadeDis) {
                    clip(-1);
                    }
                else if (dis < fadeSmooth) {
                    float v = (1-(fadeSmooth-dis)/fade);
                    //Do dither fade
                    //https://www.ronja-tutorials.com/2019/05/11/dithering.html
                    float2 screenPos = i.screenPos.xy / i.screenPos.w;
                    float2 ditherCoordinate = screenPos * _ScreenParams.xy * _DitherTex_TexelSize.xy;
                    float ditherValue = tex2D(_DitherTex, ditherCoordinate).r;
                    clip(v - ditherValue);
                    }
                return _BackFaceColor;
                }
            ENDCG
            }

        }
    }