Shader "Unlit/GradientShader"
{
	Properties
	{

		_MainTex("MainTex",2D) = "white" {}
		_LightGradient("LitGradient", 2D) = "white" {}
		_LitColor("LitColor", Color) = (1,0,0,1)
		_ShadowColor("ShadowColor", Color) = (0,0,1,1)

		_SpecGradient("SpecGradient", 2D) = "white" {}
		_SpecColor("SpecColor", Color) = (1,1,0,1)
		_SpecStart("SpecStart", Range(0, 1)) = 1
		_SpecEnd("SpecEnd", Range(0, 1)) = 0
		_SpecStrength("SpecStrength", Range(0,1)) = 1

		_RimGradient("RimGradient", 2D) = "white" {}
		_RimColor("RimColor", Color) = (0,1,1,1)
		_RimStart("RimStart", Range(0, 1)) = 1
		_RimEnd("RimEnd", Range(0, 1)) = 0
		_RimStrength("RimStrength", Range(0,1)) = 0.35

	}
		SubShader
		{
			Tags { 
			"RenderType" = "Opaque"
			"LightMode" = "ForwardBase"
			"PassFlags" = "OnlyDirectional"
			}
			LOD 100

			Cull off

			Pass
			{
				CGPROGRAM
				#pragma vertex vert
				#pragma fragment frag
				#pragma multi_compile_fwdbase

				#include "UnityCG.cginc"
				#include "AutoLight.cginc"

				struct appdata
				{
					float4 vertex : POSITION;
					float2 uv : TEXCOORD0;
					float3 normal : NORMAL;

				};

				struct v2f
				{
					float2 uv : TEXCOORD0;
					float4 pos : SV_POSITION;
					float3 worldNormal : NORMAL;
					float3 viewDir : TEXCOORD1;
					SHADOW_COORDS(2)
				};

				//Base Lit color and shadow color
				sampler2D _LightGradient;
				//float4 _LightGradient_ST;
				fixed4 _LitColor;
				fixed4 _ShadowColor;

				//Specular Setting
				sampler2D _SpecGradient;
				fixed4 _SpecColor;
				float _SpecStart;
				float _SpecEnd;
				float _SpecStrength;

				//Rim
				sampler2D _RimGradient;
				fixed4 _RimColor;
				float _RimStart;
				float _RimEnd;
				float _RimStrength;

				sampler2D _MainTex;
				float4 _MainTex_ST;

				v2f vert(appdata v)
				{
					v2f o;
					o.pos = UnityObjectToClipPos(v.vertex);
					o.worldNormal = UnityObjectToWorldNormal(v.normal);
					o.viewDir = WorldSpaceViewDir(v.vertex);

					o.uv = v.uv + _MainTex_ST.xy * _MainTex_ST.zw;
					TRANSFER_SHADOW(o)

					return o;
				}

				fixed4 frag(v2f i) : SV_Target
				{
					half4 maintex = tex2D(_MainTex,i.uv);

					//(value - from1) / (to1 - from1) * (to2 - from2) + from2;
					float shadow = SHADOW_ATTENUATION(i);

					float3 normal = normalize(i.worldNormal);
					float3 viewDir = normalize(i.viewDir);
					float NdotL = dot(_WorldSpaceLightPos0, normal);

					float3 halfVector = normalize(_WorldSpaceLightPos0 + viewDir);
					float NdotH = dot(normal, halfVector);

					float specFac = clamp((NdotL * clamp(NdotH, 0.5, 1) - _SpecStart) / (_SpecEnd - _SpecStart),0,1);
					float specValue = 1 - tex2D(_SpecGradient, specFac).r;
					fixed4 LitColor = lerp(_LitColor, _SpecColor, specValue * _SpecStrength);

					float LitFac = (NdotL + 1) / 2;
					float LitValue = tex2D(_LightGradient, NdotL).r;
					fixed4 shadowreceivedColor = lerp(_ShadowColor, LitColor, shadow);
					fixed4 shadedColor = lerp(_ShadowColor, shadowreceivedColor, LitValue);

					float rimFac = clamp((dot(normal, viewDir) - _RimStart) / (_RimEnd - _RimStart) ,0,1);
					float rimValue = tex2D(_RimGradient, rimFac).r;
					fixed4 rimColor = lerp(shadedColor, _RimColor, rimValue * _RimStrength) * maintex;

					return rimColor;

				}
				ENDCG
			}

			UsePass "Legacy Shaders/VertexLit/SHADOWCASTER"

		}
}