How do I add transparency to a cg vertex lit shader

Questions & Answers
1

I have a scrolling background shader that I am trying to add transparency two, but I can’t seem to get it working. Can anyone help me out with this?

Shader "BRS/Environment/Scrolling Background with Alpha" {
    Properties {
    	_MainTex ("Base layer (RGB)", 2D) = "white" {}
    	//_DetailTex ("2nd layer (RGB)", 2D) = "white" {}
    	_ScrollX ("Base layer Scroll speed X", Float) = 1.0
    	_ScrollY ("Base layer Scroll speed Y", Float) = 0.0
    	//_Scroll2X ("2nd layer Scroll speed X", Float) = 1.0
    	//_Scroll2Y ("2nd layer Scroll speed Y", Float) = 0.0
    	_Intensity ("Intensity", Float) = 0.5
    	_Alpha ("Alpha", Range(0.0, 1.0)) = 1.0
    }
    
    SubShader {
    	Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }
    	
    	Lighting Off 
    	Fog { Mode Off }
    	ZWrite Off
    	
    	LOD 100
    	
    		
    	CGINCLUDE
    	#pragma multi_compile LIGHTMAP_OFF LIGHTMAP_ON
    	#include "UnityCG.cginc"
    	sampler2D _MainTex;
    	//sampler2D _DetailTex;
    
    	float4 _MainTex_ST;
    	//float4 _DetailTex_ST;
    	
    	float _ScrollX;
    	float _ScrollY;
    	//float _Scroll2X;
    	//float _Scroll2Y;
    	float _Intensity;
    	float _Alpha;
    	
    	struct v2f {
    		float4 pos : SV_POSITION;
    		float2 uv : TEXCOORD0;
    		//float2 uv2 : TEXCOORD1;
    		fixed4 color : TEXCOORD1;		
    	};
    
    	
    	v2f vert (appdata_full v)
    	{
    		v2f o;
    		o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
    		o.uv = TRANSFORM_TEX(v.texcoord.xy,_MainTex) + frac(float2(_ScrollX, _ScrollY) * _Time);
    		//o.uv2 = TRANSFORM_TEX(v.texcoord.xy,_DetailTex) + frac(float2(_Scroll2X, _Scroll2Y) * _Time);
    		o.color = fixed4(_Intensity, _Intensity, _Intensity, _Alpha);
    
    		return o;
    	}
    	ENDCG
    
    
    	Pass {
    		CGPROGRAM
    		#pragma vertex vert
    		#pragma fragment frag
    		#pragma fragmentoption ARB_precision_hint_fastest		
    		fixed4 frag (v2f i) : COLOR
    		{
    			fixed4 o;
    			fixed4 tex = tex2D (_MainTex, i.uv);
    			//fixed4 tex2 = tex2D (_DetailTex, i.uv2);
    			
    			//o = (tex * tex2) * i.color;
    			o = tex * i.color;
    			
    			return o;
    		}
    		ENDCG 
    	}	
    }
    }
2

Add the blend mode after ZWrite Off:

    ...
    ZWrite Off
    Blend SrcAlpha OneMinusSrcAlpha
3

Sure. Instead of multiplying to overlay a texture with alpha, you need to use lerp.

// - Unlit

// - Scroll 3 layers /w Multiplicative op

Shader “BRS/Environment/Scroll 3 Layers” {
Properties {
_MainTex (“Base layer (RGB)”, 2D) = “white” {}
_FarTex (“2nd layer (RGB)”, 2D) = “black” {}
_NearTex (“2nd layer (RGB)”, 2D) = “black” {}
_ScrollX (“Base layer Scroll speed X”, Float) = 0.1
_ScrollY (“Base layer Scroll speed Y”, Float) = 0.0
_Scroll2X (“2nd layer Scroll speed X”, Float) = 0.5
_Scroll2Y (“2nd layer Scroll speed Y”, Float) = 0.0
_Scroll3X (“3nd layer Scroll speed X”, Float) = 1.0
_Scroll3Y (“3nd layer Scroll speed Y”, Float) = 0.0
_ColorIntensity (“Layer Multiplier”, Float) = 0.5
}

SubShader{
	Tags {"Queue"="Background" "IgnoreProjector"="True" "RenderType"="Background"}
	LOD 100
	
	ZWrite Off
	Lighting Off

	CGPROGRAM
	#pragma surface surf NoLighting

	half4 LightingNoLighting (SurfaceOutput s, half3 lightDir, half atten) {
		half4 c;
		c.rgb = s.Albedo;
		return c;
	}

	struct Input {
		float2 uv_MainTex;
		float2 uv_FarTex;
		float2 uv_NearTex;
	};
	
	sampler2D _MainTex;
	sampler2D _FarTex;
	sampler2D _NearTex;
	
	half _ScrollX;
	half _ScrollY;
	half _Scroll2X;
	half _Scroll2Y;
	half _Scroll3X;
	half _Scroll3Y;
	
	fixed _ColorIntensity;
	
	void surf (Input IN, inout SurfaceOutput o) {
		float2 mainTex_uv = IN.uv_MainTex;
		float2 farTex_uv = IN.uv_FarTex;
		float2 nearTex_uv = IN.uv_NearTex;
		
		mainTex_uv.x += _ScrollX * _Time.x;
		mainTex_uv.y += _ScrollY * _Time.x;
		
		farTex_uv.x += _Scroll2X * _Time.x;
		farTex_uv.y += _Scroll2Y * _Time.x;
		
		nearTex_uv.x += _Scroll3X * _Time.x;
		nearTex_uv.y += _Scroll3Y * _Time.x;
		
		float4 mainTex = tex2D (_MainTex, mainTex_uv);
		float4 farTex = tex2D (_FarTex, farTex_uv);
		float4 nearTex = tex2D (_NearTex, nearTex_uv);
		
		float3 previous = lerp(mainTex.rgb, farTex.rgb, farTex.a);
	    o.Albedo = lerp(previous.rgb, nearTex.rgb, nearTex.a) * _ColorIntensity;
	}
	
	ENDCG
}

}