当被光线触碰时，Unity会使物体褪色

Question

I have objects in my game I want to be invisible when they get hit by light

The effect I'm looking for is something like the lens of truth from Zelda Ocarina of Time

I got it working by doing Raycasts from the lightsource in the direction of my objects and it's corners

But now I want to see if I can get it to work like the lens of truth (if the light hits a part of the object it only fades that part.

Shader "Custom/Matte Shadow" {

Properties{
    _Color("Main Color", Color) = (1,1,1,1)
    _MainTex("Base (RGB) Trans (A)", 2D) = "white" {}
_Cutoff("Alpha cutoff", Range(0,1)) = 0.5
}

    SubShader{
    Tags{ "Queue" = "AlphaTest" "RenderType" = "TransparentCutout" }
    LOD 200
    Blend Zero SrcColor
    Offset 0, -1

    CGPROGRAM

#pragma surface surf ShadowOnly alphatest:_Cutoff fullforwardshadows

    fixed4 _Color;

    struct Input {
        float2 uv_MainTex;
    };

    inline fixed4 LightingShadowOnly(SurfaceOutput s, fixed3 lightDir, fixed atten) {
        fixed4 c;

        c.rgb = s.Albedo*atten;
        c.a = s.Alpha;
        return c;
    }

    void surf(Input IN, inout SurfaceOutput o) {
        fixed4 c = _Color;
        o.Albedo = c.rgb;
        o.Alpha = 0.0f;
    }
ENDCG
}
Fallback "Transparent/Cutout/VertexLit"
}

currently I have this shader.

it makes the object transparent but when lit it receives shadows.

The problem is that it's still visible, I need it to be invisible under the LIGHT and VISIBLE in the SHADOWS.

Answer 1

If your objects are complex enough you could modify the alpha channel per vertex based on the amount of light hitting it.

Someone used a similar approach here for fog of war. Not in C#, but to give you an idea:

function RefreshFog()
{
    while(true)
    {
        var mesh : Mesh = GetComponent(MeshFilter).mesh;
        var vertices = mesh.vertices;
        var colors = mesh.colors;

        for(i=0;i<colors.length;i++)
        {
            //if the alpha of the mesh isnt 1, add 0.25 alpha on each time
            //this should cause less of a flicker than a full reset to 1 alpha causes
            //giving the fog a gradual regrowth feel
            if(colors[i].a <= 1)
            {
                //getting the current colours alpha in a var
                var f : float = colors[i].a;
                //incrementing the alpha by 1/4
                f += 0.1;
                //f shouldnt go above 1, but incase this sets the alpha correctly
                if(f > 1)
                {
                    f = 1;
                }
                colors[i].a = f;

            }

        }
        mesh.colors = colors;

        yield WaitForSeconds(1);
    }
}