Multiply blend mode shader for Spine.

Skeleton PMAMultiply.shader

// Spine/Skeleton PMA Multiply
// - single color multiply tint
// - unlit
// - Premultiplied alpha Multiply blending
// - No depth, no backface culling, no fog.
// - ShadowCaster pass

Shader "Spine/Skeleton PMA Multiply" {
	Properties {
		_Color ("Tint Color", Color) = (1,1,1,1)
		[NoScaleOffset] _MainTex ("MainTex", 2D) = "black" {}
		_Cutoff ("Shadow alpha cutoff", Range(0,1)) = 0.1
	}

	SubShader {
		Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }
		LOD 100

		Fog { Mode Off }
		Cull Off
		ZWrite Off
		Blend DstColor OneMinusSrcAlpha
		Lighting Off

		Pass {
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#include "UnityCG.cginc"
			uniform sampler2D _MainTex;
			uniform float4 _Color;

			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;
				o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
				o.uv = v.uv;
				o.vertexColor = v.vertexColor * float4(_Color.rgb * _Color.a, _Color.a); // Combine a PMA version of _Color with vertexColor.
				return o;
			}

			float4 frag (VertexOutput i) : COLOR {
				float4 texColor = tex2D(_MainTex, i.uv);
				return (texColor * i.vertexColor);
			}
			ENDCG
		}

		Pass {
			Name "Caster"
			Tags { "LightMode"="ShadowCaster" }
			Offset 1, 1

			ZWrite On
			ZTest LEqual

			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma multi_compile_shadowcaster
			#pragma fragmentoption ARB_precision_hint_fastest
			#include "UnityCG.cginc"
			struct v2f { 
				V2F_SHADOW_CASTER;
				float2 uv : TEXCOORD1;
			};

			uniform float4 _MainTex_ST;

			v2f vert (appdata_base v) {
				v2f o;
				TRANSFER_SHADOW_CASTER(o)
				o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
				return o;
			}

			uniform sampler2D _MainTex;
			uniform fixed _Cutoff;

			float4 frag (v2f i) : COLOR {
				fixed4 texcol = tex2D(_MainTex, i.uv);
				clip(texcol.a - _Cutoff);
				SHADOW_CASTER_FRAGMENT(i)
			}
			ENDCG
		}
	}
}