Shader "Unlit/triplanar"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
                float4 tangent : TANGENT;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float3 worldPos : TEXCOORD1;
                float3 tangentForward : TEXCOORD3;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

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

                fixed3 worldNormal = UnityObjectToWorldNormal(v.normal);
                fixed3 worldTangent = UnityObjectToWorldDir(v.tangent.xyz);
                fixed3 worldBinormal = cross(worldNormal, worldTangent) * v.tangent.w;

                float4x4 tangentToWorld = float4x4(worldTangent.x, worldBinormal.x, worldNormal.x, 0.0,
                    worldTangent.y, worldBinormal.y, worldNormal.y, 0.0,
                    worldTangent.z, worldBinormal.z, worldNormal.z, 0.0,
                    0.0, 0.0, 0.0, 1.0);

                o.tangentForward = mul(tangentToWorld,float4(0, 0, 1, 0)).xyz;
                o.tangentForward = mul(unity_WorldToObject, o.tangentForward);
                return o;
            }

            float4 CalculateContrast(float contrastValue, float4 colorTarget)
            {
                float t = 0.5 * (1.0 - contrastValue);
                return mul(float4x4(
                    contrastValue, 0, 0, t,
                    0, contrastValue, 0, t,
                    0, 0, contrastValue, t,
                    0, 0, 0, 1), colorTarget);
            }

            fixed4 frag (v2f i) : SV_Target
            {
                float3 pos = mul(unity_WorldToObject, i.worldPos) / 1024;

                float3 dir = pow(abs(i.tangentForward), 160);
                dir /= dot(dir, 1);
                dir = CalculateContrast(512, float4(dir,0)).rgb;

                float2 uvs = pos.rg * dir.z + pos.gb * dir.x + pos.rb * dir.y;
                fixed4 col = tex2D(_MainTex, uvs);
                return col;
            }
            ENDCG
        }
    }
}