[Polybrush] Vertex Painting with Transparency

Unity Engine
1

Hi,

I am trying to create a Plane wich is part vertex painted, part transparent. In other words, I would like to have a transparent plane, then start painting on it with Polybrush. Wherever I don’t put vertex paint on, I want the plane to remain transparent.

I have tried doing this using the shader Polybrush/Standard Vertex Color.

However, I am having a problem. While the shader does have an alpha setting in the inspector, modifying this setting does not seem to achieve anything. My plane always remains opaque.

Can someone help me solve this?

Is it perhaps a bug in the shader code?

Thanks

2

The builtin shader probably just doesn’t support transparency.
Here’s something i stitched together that should work (it uses color for transparency, not the vertex alpha, as you said):

Shader "Custom/VertexColoredTransparent" {
    Properties {
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
        _Glossiness ("Smoothness", Range(0,1)) = 0.5
        _Metallic ("Metallic", Range(0,1)) = 0.0
        _Cutoff("Alpha Cutoff", Range(0,1)) = 0.5
    }
    SubShader {
        Tags { "RenderType"="Transparent" "Queue"="Transparent"}
        LOD 200
        blend SrcAlpha OneMinusSrcAlpha

        CGPROGRAM
        // Physically based Standard lighting model, and enable shadows on all light types
        #pragma surface surf Standard fullforwardshadows alphatest:_Cutoff addshadow

        // Use shader model 3.0 target, to get nicer looking lighting
        #pragma target 3.0

        sampler2D _MainTex;

        struct Input {
            float2 uv_MainTex;
            float4 color:COLOR;
        };

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
        // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
        // #pragma instancing_options assumeuniformscaling
        UNITY_INSTANCING_BUFFER_START(Props)
            // put more per-instance properties here
        UNITY_INSTANCING_BUFFER_END(Props)

        void surf (Input IN, inout SurfaceOutputStandard o) {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color*IN.color;
            o.Albedo = c.rgb;
            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a*(1-IN.color);
        }
        ENDCG
    }
    FallBack "Transparent/Cutout/VertexLit"
}