Health "tattoo" projector shader issue

Graphics Shaders & Materials
1

Im making a VR game and i needed a good way of showing the player health, so i decided to show it as a “tattoo” that can change like a ´health bar during runtime. After some digging it seemed like the best way of doing this was using a custom projector shader. Since i have no experience im amazed i managed to get it working, BUT i got issues with projection on the other side of the model and saw that the standard projectors solve this using a falloff texture. The issue is that i cant get it to work together with the falloff code. Either i get “show through” or the “bar adjustment” dont work.

Here is the code, first texture is a mask to project whatever shape you want, and the alpha will control the “bar adjust” thing. The commended lines are the falloff thing i got from the standard projector and that i cant seem to get to work together with the rest.

Shader "Projector/Healthbar" {
    Properties {
        _MaskTex ("Cookie", 2D) = "white" {}
        _FalloffTex ("FallOff", 2D) = "white" {}
        _Color ("Color", Color) = (1,1,1,1)
    }
    Subshader {
        Tags {"Queue"="Transparent"}
        Pass {
            ZWrite Off
            ColorMask RGB
            Blend DstColor Zero
            Offset -1, -1

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fog
            #include "UnityCG.cginc"
           
            struct v2f {
                float4 uvMask : TEXCOORD0;
                float4 uvFalloff : TEXCOORD1;
                UNITY_FOG_COORDS(2)
                float4 pos : SV_POSITION;
            };
           
            float4x4 unity_Projector;
            float4x4 unity_ProjectorClip;
           
            v2f vert (float4 vertex : POSITION)
            {
                v2f o;
                o.pos = mul (UNITY_MATRIX_MVP, vertex);
                o.uvMask = mul (unity_Projector, vertex);
                o.uvFalloff = mul (unity_ProjectorClip, vertex);
                UNITY_TRANSFER_FOG(o,o.pos);
                return o;
            }
           
            sampler2D _MaskTex;
            sampler2D _FalloffTex;
            float4 _Color;
           
            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 texS = tex2Dproj (_MaskTex, UNITY_PROJ_COORD(i.uvMask));
                texS.a = 1.0 - texS.a;

                //fixed4 texF = tex2Dproj (_FalloffTex, UNITY_PROJ_COORD(i.uvFalloff));
                //fixed4 res = lerp(fixed4(1,1,1,0), texS, texF.a);

                fixed4 res = 1 - texS;
                //res = 1 - res;
                if (res.r == 1)
                    res = floor((1 - i.uvMask.y) + _Color.a * res);

                float4 tmp = 1 - _Color;
                tmp.a = 1;
                UNITY_APPLY_FOG_COLOR(i.fogCoord, res, fixed4(1,1,1,1));
                return 1 - (res * tmp);
            }
            ENDCG
        }
    }
}
2

You’re better off using a custom surface shader rather than a projector. You can use a secondary UV to map where the tattoo should show up.

3

Well, as i said, i suck at shaders so i have no idea how to make that work and how to place it on my character where i want it to be : p