"Spine/Special/Skeleton Grayscale" shader

## Spine-Special-Skeleton-Grayscale.shader
// - Unlit
// - Premultiplied Alpha Blending (Optional straight alpha input)
// - Double-sided, no depth

Shader "Spine/Special/Skeleton Grayscale" {
	Properties {
		_GrayPhase ("Phase", Range(0, 1)) = 1
		[NoScaleOffset] _MainTex ("MainTex", 2D) = "white" {}
		_Cutoff ("Shadow alpha cutoff", Range(0,1)) = 0.1
		[Toggle(_STRAIGHT_ALPHA_INPUT)] _StraightAlphaInput("Straight Alpha Texture", Int) = 0
	}
	SubShader {
		Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" "PreviewType"="Plane" }
		Blend One OneMinusSrcAlpha
		Cull Off
		ZWrite Off
		Lighting Off

		Pass {
			CGPROGRAM
			#pragma shader_feature _ _STRAIGHT_ALPHA_INPUT
			#pragma vertex vert
			#pragma fragment frag
			#include "UnityCG.cginc"
			sampler2D _MainTex;
			float _GrayPhase;

			struct VertexInput {
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
				float4 vertexColor : COLOR;
			};

			struct VertexOutput {
				float4 pos : SV_POSITION;
				float2 uv : TEXCOORD0;
				float4 vertexColor : COLOR;
			};

			VertexOutput vert (VertexInput v) {
				VertexOutput o = (VertexOutput)0;
				o.uv = v.uv;
				o.vertexColor = v.vertexColor;
				o.pos = UnityObjectToClipPos(v.vertex);
				return o;
			}

			float4 frag (VertexOutput i) : COLOR {
				float4 rawColor = tex2D(_MainTex,i.uv);
				float finalAlpha = (rawColor.a * i.vertexColor.a);

				#if defined(_STRAIGHT_ALPHA_INPUT)
				rawColor.rgb *= rawColor.a;
				#endif

				rawColor.rgb *= i.vertexColor.rgb;

				float3 finalColor = lerp(rawColor.rgb, dot(rawColor.rgb, float3(0.3, 0.59, 0.11)), _GrayPhase);
				return fixed4(finalColor, finalAlpha);
			}
			ENDCG
		}

		Pass {
			Name "Caster"
			Tags { "LightMode"="ShadowCaster" }
			Offset 1, 1
			ZWrite On
			ZTest LEqual

			Fog { Mode Off }
			Cull Off
			Lighting Off

			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma multi_compile_shadowcaster
			#pragma fragmentoption ARB_precision_hint_fastest
			#include "UnityCG.cginc"
			sampler2D _MainTex;
			fixed _Cutoff;

			struct VertexOutput {
				V2F_SHADOW_CASTER;
				float2 uv : TEXCOORD1;
			};

			VertexOutput vert (appdata_base v) {
				VertexOutput o;
				o.uv = v.texcoord;
				TRANSFER_SHADOW_CASTER(o)
				return o;
			}

			float4 frag (VertexOutput i) : COLOR {
				fixed4 texcol = tex2D(_MainTex, i.uv);
				clip(texcol.a - _Cutoff);
				SHADOW_CASTER_FRAGMENT(i)
			}
			ENDCG
		}
	}
	FallBack "Diffuse"
}