How to fix normals on shader

Question

I have a problem with a shader I made/cobbled together from bits of code

Initially my plan was to was a shader at runtime Shader on disabled object? But this seems to be the wrong thing to do, as its my understanding now that shaders can't be swapped at runtime.

So I would like to be able to correct the shader I have so that I can fade from colour to greyscale but not have part of the model disappearing. I really don't understand shaders...

The code I have so far

Shader "Custom/GreyScaleToColour"
{
Properties
{
    [PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}
    _Color("Tint", Color) = (1,1,1,1)
    [MaterialToggle] PixelSnap("Pixel snap", Float) = 0
    [HideInInspector] _RendererColor("RendererColor", Color) = (1,1,1,1)
    [HideInInspector] _Flip("Flip", Vector) = (1,1,1,1)
    [PerRendererData] _AlphaTex("External Alpha", 2D) = "white" {}
    [PerRendererData] _EnableExternalAlpha("Enable External Alpha", Float) = 0
    _EffectAmount("Effect Amount", Range(0, 1)) = 1.0
    _Brightness("Brightness", Range(0, 1.5)) = 0.5
}

    SubShader
    {
        Tags
        {
            "Queue" = "Transparent"
            "IgnoreProjector" = "True"
            "RenderType" = "Transparent"
            "PreviewType" = "Plane"
            "CanUseSpriteAtlas" = "True"
        }

        //Cull Off
        Lighting Off
        ZWrite Off
        Blend One OneMinusSrcAlpha

        CGPROGRAM
        #pragma surface surf Lambert vertex:vert nofog nolightmap nodynlightmap keepalpha noinstancing
        #pragma multi_compile _ PIXELSNAP_ON
        #pragma multi_compile _ ETC1_EXTERNAL_ALPHA
        #include "UnitySprites.cginc"

        struct Input
        {
            float2 uv_MainTex;
            fixed4 color;
        };

        void vert(inout appdata_full v, out Input o)
        {
            v.vertex.xy *= _Flip.xy;

            #if defined(PIXELSNAP_ON)
            v.vertex = UnityPixelSnap(v.vertex);
            #endif

            UNITY_INITIALIZE_OUTPUT(Input, o);
            o.color = v.color * _Color * _RendererColor;
        }
        uniform float _EffectAmount;
        uniform float _Brightness;

        void surf(Input IN, inout SurfaceOutput o)
        {
            fixed4 c = SampleSpriteTexture(IN.uv_MainTex) * IN.color;
            c.rgb = lerp(c.rgb, dot(c.rgb, float3(0.3, 0.59, 0.11)), _EffectAmount);
            //o.Albedo = c.rgb * c.a;
            o.Albedo = c.rgb * _Brightness;
            //o.Albedo = (c.r + c.g + c.b) / 3 * _Brightness;
            o.Alpha = c.a;
        }
        ENDCG
    }

        Fallback "Sprite/Diffuse"
}

Part of the model disappears...

Strange artifacts appear

How it should look approximately

With thanks Natalie

Answer 1

Regarding the swapping of Shaders at runtime - you don't need to swap the Shaders at runtime. You can simply enable/disable different GameObjects with the correct shaders on them.

// Assigned in the Editor
GameObject disabledGO; // Contains the Material with the Disabled Shader
GameObject normalGO; // Contains the Material with the Normal Shader

bool isDisabled = false;

private void Start()
{
    disabledGO.SetActive(isDisabled);
    normalGO.SetActive(!isDisabled);
}

private void Update()
{
    if (Input.GetKey(KeyCode.E))
    {
        isDisabled = !isDisabled;
        disabledGO.SetActive(isDisabled);
        normalGO.SetActive(!isDisabled);
    }
}