Trying to get vertex color from SpriteRenderer in shader

Unity Engine
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1

here’s the code:

Shader "Debug/VertexColor"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" { }      // SpriteRenderer needs this
    }

    SubShader
    {
        Tags
        {
            "Queue" = "Transparent"
            "RenderType" = "Transparent"
            "RenderPipeline" = "UniversalPipeline"
        }
        
        Cull Off
        ZWrite Off
        ZTest Always
        Blend SrcAlpha OneMinusSrcAlpha
        
        Pass
        {
            Tags { "LightMode" = "Universal2D" }

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct Attributes
            {
                float3 position   : POSITION;
                float4 color      : COLOR;
            };
            
            struct v2f
            {
                float4 position : SV_POSITION;
                float4 color : COLOR;
            };
            
            v2f vert(Attributes v)
            {
                v2f o;
                o.position = UnityObjectToClipPos(v.position);
                o.color = v.color;
                return o;
            }
            
            float4 frag(v2f i) : SV_Target
            {
                return i.color;
            }
            
            ENDCG
        }
    }
}

I’m using SpriteRenderer to test the material, and the returned i.color is always white.
I created another shader by ShaderGraph, with a Vertex Color node inside, and it performed well.
I created my own mesh with mesh.SetColors, and render it using MeshRenderer, this shader then can display vertex color as well.
Why this shader fails to access vertex color from SpriteRenderer?
I think there’s something I’ve missed…
btw I’m using URP 2D.

2

The issue you’re facing occurs because SpriteRenderer in Unity doesn’t use per-vertex color attributes directly in the same way as a MeshRenderer. Instead, it handles color by applying a uniform tint color (_Color) across the entire sprite, and this tint is not stored in the vertex attributes (COLOR semantics).

Updated Shader

Shader "Debug/VertexColor"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" { }  
        _Color ("Color Tint", Color) = (1, 1, 1, 1)  // SpriteRenderer color
    }

    SubShader
    {
        Tags
        {
            "Queue" = "Transparent"
            "RenderType" = "Transparent"
            "RenderPipeline" = "UniversalPipeline"
        }

        Cull Off
        ZWrite Off
        ZTest Always
        Blend SrcAlpha OneMinusSrcAlpha

        Pass
        {
            Tags { "LightMode" = "Universal2D" }

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct Attributes
            {
                float3 position : POSITION;
                float4 color : COLOR;
            };

            struct v2f
            {
                float4 position : SV_POSITION;
                float4 color : COLOR;
            };

            UNITY_DECLARE_COLOR;

            v2f vert(Attributes v)
            {
                v2f o;
                o.position = UnityObjectToClipPos(v.position);
                o.color = v.color * UNITY_ACCESS_COLOR; // Multiply by SpriteRenderer color
                return o;
            }

            float4 frag(v2f i) : SV_Target
            {
                return i.color;
            }

            ENDCG
        }
    }
}

Hope this helps

3

wow, this is the first time I realize that Vertex Color is not only the color attribute from vertex input… Thanks a lot.

4

what, wait, this post Changing the Sprite Renderer's Color property has no effect in my Custom Shader is telling me that it access ‘color’ vertex input attribute…? I’m now confused because _Color looks not working somethimes, for example this shader doesn’t work in unity 6:

  Shader "Custom/RectAlphaFade"
  {
      Properties
      {
          _MainTex ("Texture", 2D) = "white" {}
          _Color ("Color", Color) = (1,1,1,1)
          _OpaqueMin ("Opaque Rect Min (World)", Vector) = (-10,-10,0)
          _OpaqueMax ("Opaque Rect Max (World)", Vector) = (10,10,0)
          _TransparentMin ("Transparent Rect Min (World)", Vector) = (-5,-5,0)
          _TransparentMax ("Transparent Rect Max (World)", Vector) = (5,5,0)
      }
      SubShader
      {
          Tags { "RenderType"="Transparent" "Queue"="Transparent" }
          LOD 100
          Blend SrcAlpha OneMinusSrcAlpha, One OneMinusSrcAlpha
          ZWrite Off
  
          Pass
          {
              CGPROGRAM
              #pragma vertex vert
              #pragma fragment frag
              #include "UnityCG.cginc"
  
              struct appdata
              {
                  float4 vertex : POSITION;
              };
  
              struct v2f
              {
                  float4 pos : SV_POSITION;
                  float3 worldPos : TEXCOORD0;
              };
  
              fixed4 _Color;
              float4 _OpaqueMin, _OpaqueMax;
              float4 _TransparentMin, _TransparentMax;
  
              v2f vert (appdata v)
              {
                  v2f o;
                  o.pos = UnityObjectToClipPos(v.vertex);
                  o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                  return o;
              }

              fixed4 frag (v2f i) : SV_Target
              {
                  return _Color;
              }
              ENDCG
          }
      }
  }