Fragment shader shows alpha, surface shader doesn't

Unity Engine
1

I have 2 shaders that do the same, which is nothing… just pass the color.

As a fragment shader

Shader "EffectBakers/FogBaker"
    {
        Properties
        {
            [PerRendererData] _MainTex ("Color (RGB) Alpha (A)", 2D) = "black" {}
            [MaterialToggle] PixelSnap( "Pixel snap", Float) = 0
  
            [HideInInspector]_FogTexture( "Fog Ramp Texture", 2D) = "black" { }
            [HideInInspector]_01FogDepthVerticals( "Linear Depth 01 And Verticals", Vector) = (0.0, 0.0, 0.0, 0.0)        
            [HideInInspector]_IsWarm( "Warm texture or Cold texture", Range(0,1)) = 0
        }
  
        SubShader
        {
            Tags
            {
                "Queue"="Transparent"
                "IgnoreProjector"="True"
                "RenderType"="Transparent"
                "PreviewType"="Plane"
                "CanUseSpriteAtlas"="True"
            }
  
            Cull Off
            Lighting Off
            ZWrite Off
            Fog { Mode Off }
            Blend One OneMinusSrcAlpha
  
            Pass
            {
            CGPROGRAM
                #pragma vertex vert
                #pragma fragment frag
                #pragma multi_compile DUMMY PIXELSNAP_ON
                #include "UnityCG.cginc"
  
                struct appdata_t
                {
                    float4 vertex   : POSITION;
                    float2 texcoord : TEXCOORD0;
                };
  
                struct v2f
                {
                    float4 vertex   : SV_POSITION;
                    half2 texcoord  : TEXCOORD0;
                };
  
                fixed4 _Color;
  
                v2f vert(appdata_t IN)
                {
                    v2f OUT;
                    OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
                    OUT.texcoord = IN.texcoord;
                    #ifdef PIXELSNAP_ON
                    OUT.vertex = UnityPixelSnap (OUT.vertex);
                    #endif
  
                    return OUT;
                }
  
                sampler2D _MainTex;
  
                fixed4 frag(v2f IN) : SV_Target
                {
                    fixed4 c = tex2D(_MainTex, IN.texcoord);
                    c.rgb *= c.a;
                    return c;
                }
            ENDCG
            }
        }
    }

And as a surface Shader:

Shader "EffectBakers/FogBaker"
        {
            Properties
            {
                _MainTex ("Color (RGB) Alpha (A)", 2D) = "white" {}
                _Color("Tint", Color) = (1, 1, 1, 1)
                [MaterialToggle] PixelSnap( "Pixel snap", Float) = 0
      
                [HideInInspector]_FogTexture( "Fog Ramp Texture", 2D) = "black" { }
                [HideInInspector]_01FogDepthVerticals( "Linear Depth 01 And Verticals", Vector) = (0.0, 0.0, 0.0, 0.0)        
                [HideInInspector]_IsWarm( "Warm texture or Cold texture", Range(0,1)) = 0
            }
      
            SubShader
            {
                Tags
                {
                    "Queue"="Transparent"
                    "IgnoreProjector"="True"
                    "RenderType"="Transparent"
                    "PreviewType"="Plane"
                    "CanUseSpriteAtlas"="True"
                }
      
                Cull Off
                Lighting Off
                ZWrite Off
                Fog { Mode Off }
                Blend One OneMinusSrcAlpha
      
                CGPROGRAM
                #pragma surface surf Lambert vertex:vert nofog keepalpha
                #pragma target 3.0
                #pragma multi_compile _PIXELSNAP_ON 
      
                sampler2D _MainTex;     
      
                fixed4 _Color;     
      
                struct Input
                {
                    float2 uv_MainTex ;
                    float3 worldPos;
                } ;
      
              
                void vert( inout appdata_full v, out Input o )
                {
                    #if defined( PIXELSNAP_ON )
                        v.vertex = UnityPixelSnap(v_.vertex);
                    #endif
      
                        UNITY_INITIALIZE_OUTPUT(Input, o);
                    o.worldPos = mul( _Object2World, v.vertex );
                }
      
                sampler2D _FogTexture;  
                fixed4 _01FogDepthVerticals;
                int _IsWarm;
      
      
                void surf(Input i, inout SurfaceOutput o)
                {
                    fixed4 color = tex2D( _MainTex, i.uv_MainTex );      
                  
                    o.Albedo = color.rgb * color.a;
                    o.Alpha = color.a;
                }
                ENDCG
            }
      
            FallBack "Transparent/Cutout/VertexLit"
        }

why the fragment shader displays the sprite with alpha channel and no problems, but the surface one shows the transparency as black and everything is opaque?

Thanks for the help.

2

Try

#pragma surface surf Lambert vertex:vert nofog alpha:premul

instead of keepalpha. As for why that works and the other doesn’t … I don’t have a good answer.

3

Thanks for the help.

alpha:premul shows nothing but black… (Not even all transparent)

4

The surface shader is using a Lambert lighting model. Do you have no lighting in your scene? If you don’t want to have lighting do anything there’s no reason to use a surface shader.

5

It’s actually a baker, I Blit a texture to get a new one with some process and then use it in the game, so I don’t need to take the lightning in account at all. I’ll use a fragment shader, but I would like to know why a surface shader doesn’t have alpha channel in this case.