Shader "Custom/shd-watercol-post"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _DispTex ("Texture", 2D) = "white" {}
        _PaintTex ("Texture", 2D) = "white" {}
        _PaperTex ("Texture", 2D) = "white" {}
        _GrowInk ("Grow ink", Range(0.0, 1.0)) = 1.0
        _RadiusInk ("Radius ink", Float) = 0.2
    }
    SubShader
    {
        // No culling or depth
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

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

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            sampler2D _MainTex;
            sampler2D _DispTex;
            sampler2D _PaintTex;
            sampler2D _PaperTex;
            float _GrowInk;
            float _RadiusInk;

            fixed intensity(fixed3 a)
            {
                return a.r * 0.3 + a.g * 0.59 + a.b * 0.11;
            }

            fixed3 blended(fixed3 a, fixed3 b, fixed disp)
            {
                fixed ai = intensity(a);
                fixed bi = intensity(b);

                fixed alpha = (ai > bi) ? (0.35 + 0.5 * disp) : 1.075;
                fixed3 c = alpha * a + (1.0 - alpha) * b;

                return c;
            }

            fixed3 rgbmin(fixed3 c)
            {
                return max(c, 0.275);
            }

            fixed4 brush(fixed2 uv)
            {
                // må bruka noko slags verdsposisjon istf uv/skjerm for ser rart ut i rørelse!

                // akkurat no kan ting ikkje bli heilt svarte om det er lite ljos, fiks!

                fixed ratio = _ScreenParams.y / _ScreenParams.x;
                fixed factor = (_ScreenParams.x / 1920.0);
                fixed2 uv2 = fixed2(uv.x, uv.y * ratio) * 3.0;
                fixed2 uv3 = fixed2(uv.x, uv.y * ratio) * 3.0;

                fixed disp = tex2D(_DispTex, uv2 * 0.5).r;
                fixed paint = tex2D(_PaintTex, uv2 * 1.75).r;
                fixed paper = tex2D(_PaperTex, uv3 * 4.0 * factor).r;

                //float depth = clamp(tex2D(_CameraDepthTexture, uv).r - 0.15, 0.0, 0.5) * 2.2;
                //float offs = _Offset + pow(min(depth, 2.0), 21.0);

                fixed4 col = tex2D(_MainTex, uv);
                float offs = 12.0 - disp * paint * paper;
                fixed2 o = fixed2(offs / _ScreenParams.x, offs / _ScreenParams.y);

                o *= disp * 0.5;

                fixed2 curve2 = fixed2(0.35, 0.5) + paint * 0.4;
                fixed fy = -0.5;

                fixed3 a = tex2D(_MainTex, uv + fixed2(0.0, o.y * curve2.y)).rgb;
                fixed3 b = tex2D(_MainTex, uv + fixed2(o.x * curve2.x, o.y * curve2.y * fy)).rgb;
                fixed3 c = tex2D(_MainTex, uv + fixed2(o.x * curve2.x, -o.y * curve2.y * fy)).rgb;
                fixed3 d = tex2D(_MainTex, uv + fixed2(0.0, -o.y * curve2.y)).rgb;
                fixed3 e = tex2D(_MainTex, uv + fixed2(-o.x * curve2.x, -o.y * curve2.y * fy)).rgb;
                fixed3 f = tex2D(_MainTex, uv + fixed2(-o.x * curve2.x, o.y * curve2.y * fy)).rgb;

                fixed3 corr = col.rgb * fixed3(1.2, 0.85, 1.0);

                //disp = paint * 2.5;
                disp *= 1.6;

                col.rgb = blended(col.rgb, a, disp * 1.5);
                col.rgb = blended(col.rgb, b, disp * 0.25);
                col.rgb = blended(col.rgb, c, disp * 0.5);
                col.rgb = blended(col.rgb, d, disp);
                col.rgb = blended(col.rgb, e, disp * 0.5);
                col.rgb = blended(col.rgb, f, disp);

                col.rgb = rgbmin(col.rgb);
                a.rgb = rgbmin(a.rgb);
                b.rgb = rgbmin(b.rgb);
                c.rgb = rgbmin(c.rgb);
                d.rgb = rgbmin(d.rgb);
                e.rgb = rgbmin(e.rgb);
                f.rgb = rgbmin(f.rgb);

                col *= paper * 1.15;

                return col;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                //fixed4 col = tex2D(_MainTex, i.uv);
                fixed4 col = brush(i.uv);
                return col;
            }
            ENDCG
        }
    }
}