Shader "NPR/Trippy Plasma Skull"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
		_Tint("Colour Tint", Color) = (1,1,1,1)
		_Speed("Speed", Range(1, 100)) = 10
		_Scale1("Scale 1", Range(0.1, 10)) = 2
		_Scale2("Scale 2", Range(0.1, 10)) = 2
		_Scale3("Scale 3", Range(0.1, 10)) = 2
		_Scale4("Scale 4", Range(0.1, 10)) = 2
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" "LightMode" = "ForwardBase"}
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

			#include "UnityCG.cginc"
			#include "Lighting.cginc"

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

            struct v2f
            {
                float2 uv : TEXCOORD0;
				float3 diffusecolor : COLOR;
                float4 vertex : SV_POSITION;
				float3 worldPos : TEXCOORD1;
				float3 worldNormal : TEXCOORD2;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
			float2 uv_MainTex;
			float3 worldPos;
			float4 _Tint;
			float _Speed;
			float _Scale1;
			float _Scale2;
			float _Scale3;
			float _Scale4;
			fixed4 _Diffuse;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
				o.worldPos = mul(unity_ObjectToWorld, v.vertex);
				o.worldNormal = mul(v.normal, (float3x3)unity_WorldToObject);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
				const float PI = 3.141592653589793238462;
				float timePassed = _Time.x * _Speed;

				//screen coordinates: small values for the sin
				float xpos = i.vertex.x * 0.001;
				float ypos = i.vertex.y * 0.001;

				//vertical
				float plasmaColour = sin(i.worldPos.x * _Scale1 + timePassed);

				//horizontal
				plasmaColour += sin(i.worldPos.z * _Scale2 + timePassed);

				//diagonal
				plasmaColour += sin(_Scale3 * worldPos.x * sin(timePassed / 2.0) + worldPos.z * cos(timePassed / 3) + timePassed);

				//circular
				float plasmaColour1 = pow(xpos + 0.5 * sin(timePassed / 5), 2);
				float plasmaColour2 = pow(ypos + 0.5 * sin(timePassed / 5), 2);
				plasmaColour += sin(sqrt(_Scale4 * (plasmaColour1 + plasmaColour2) + 1 + timePassed));

				//get ambient term
				float4 ambient = UNITY_LIGHTMODEL_AMBIENT.xyzw;
				float worldNormal = normalize(i.worldNormal);

				fixed4 worldLightDir = normalize(_WorldSpaceLightPos0.xyzw);
				//compute diffuse term
				fixed4 diffuse = _LightColor0.rgba *_Diffuse.rgba * saturate(dot(worldNormal, worldLightDir));
				fixed3 diffuseColor = ambient + diffuse;

                float finalColor = tex2D(_MainTex, i.uv) * _Tint * diffuseColor;

				// vertical color
				finalColor.r = sin(plasmaColour / 4.0 * PI);

                return finalColor;
            }
            ENDCG
        }
    }
}