Fresnel shaders, HDR, Overlay

FresnelOverlay_Add1.shader

Shader "Custom/FresnelOverlay_Add1"
{
    Properties
    {
        [HDR]_RimColor   ("Fresnel Color (HDR)", Color) = (3,3,3,1)
        _RimPower        ("Fresnel Power", Range(0.1, 8)) = 3.0
        _RimStrength     ("Fresnel Strength", Range(0, 10)) = 1.0
        _DoubleSided     ("Double-Sided (0=Back,1=Off,2=Front)", Range(0,2)) = 2
        _DepthBias       ("Depth Bias (to avoid misses)", Float) = 0.0
    }

    SubShader
    {
        Tags { "Queue"="Transparent+10" "RenderType"="Transparent" }

        // Additive overlay on top of what’s already rendered
        Blend One One
        ZWrite Off
        ZTest Equal          // draw only where depth already matches (on the mesh)
        Cull Back            // default: draw front faces only
        ColorMask RGB

        Pass
        {
            CGPROGRAM
            #pragma vertex   vert
            #pragma fragment frag
            #pragma target 3.0
            #pragma multi_compile_instancing

            #include "UnityCG.cginc"

            float4 _RimColor;
            float  _RimPower;
            float  _RimStrength;
            float  _DoubleSided;  // 0=Back, 1=Off (both), 2=Front
            float  _DepthBias;

            struct appdata
            {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct v2f
            {
                float4 pos      : SV_POSITION;
                float3 worldPos : TEXCOORD0;
                float3 worldNrm : TEXCOORD1;
                UNITY_VERTEX_INPUT_INSTANCE_ID
                UNITY_VERTEX_OUTPUT_STEREO
            };

            v2f vert (appdata v)
            {
                v2f o;
                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_OUTPUT(v2f, o);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);

                float3 worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                float3 worldNrm = UnityObjectToWorldNormal(v.normal);

                // Optional tiny depth bias to make ZTest Equal more forgiving
                float4 clip = UnityObjectToClipPos(v.vertex);
                clip.z += _DepthBias * clip.w;

                o.pos      = clip;
                o.worldPos = worldPos;
                o.worldNrm = worldNrm;
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                // Handle sidedness quickly
                float3 N = normalize(i.worldNrm);
                float3 V = normalize(_WorldSpaceCameraPos - i.worldPos);

                // Which faces to keep:
                //  Front: dot(N,V) > 0
                //  Back:  dot(N,V) < 0
                //  Both:  no discard
                float ndotv = dot(N, V);
                if (_DoubleSided < 0.5)        // Back faces only
                {
                    if (ndotv > 0) discard;
                }
                else if (_DoubleSided > 1.5)   // Front faces only
                {
                    if (ndotv < 0) discard;
                }
                // else: both sides

                // Fresnel
                ndotv = saturate(abs(ndotv));  // abs for double-sided consistency
                float rim = pow(1.0 - ndotv, _RimPower);

                float3 color = _RimColor.rgb * (rim * _RimStrength);
                return float4(color, 1);
            }
            ENDCG
        }
    }

    Fallback Off
}

FresnelOverlay_Add2.shader

Shader "Custom/FresnelOverlay_Add2"
{
    Properties
    {
        [HDR]_RimColor      ("Fresnel Color (HDR)", Color) = (3,3,3,1)
        _RimPower           ("Fresnel Power", Range(0.1, 8)) = 3.0
        _RimStrength        ("Fresnel Strength", Range(0, 10)) = 1.0
        [HDR]_OverlayColor  ("Overlay Color (HDR, fill)", Color) = (0,0,0,0)
        _DoubleSided        ("Double-Sided (0=Back,1=Both,2=Front)", Range(0,2)) = 2
        _DepthBias          ("Depth Bias (to avoid misses)", Float) = 0.0
    }

    SubShader
    {
        Tags { "Queue"="Transparent+10" "RenderType"="Transparent" }

        // Additive overlay on top of what's already rendered
        Blend One One
        ZWrite Off
        ZTest Equal          // only on the mesh where depth matches
        Cull Back
        ColorMask RGB

        Pass
        {
            CGPROGRAM
            #pragma vertex   vert
            #pragma fragment frag
            #pragma target 3.0
            #pragma multi_compile_instancing

            #include "UnityCG.cginc"

            float4 _RimColor;
            float  _RimPower;
            float  _RimStrength;
            float4 _OverlayColor;
            float  _DoubleSided;  // 0=Back, 1=Both, 2=Front
            float  _DepthBias;

            struct appdata
            {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct v2f
            {
                float4 pos      : SV_POSITION;
                float3 worldPos : TEXCOORD0;
                float3 worldNrm : TEXCOORD1;
                UNITY_VERTEX_INPUT_INSTANCE_ID
                UNITY_VERTEX_OUTPUT_STEREO
            };

            v2f vert (appdata v)
            {
                v2f o;
                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_OUTPUT(v2f, o);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);

                float4 clip = UnityObjectToClipPos(v.vertex);
                clip.z += _DepthBias * clip.w; // tiny bias if needed

                o.pos      = clip;
                o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                o.worldNrm = UnityObjectToWorldNormal(v.normal);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                float3 N = normalize(i.worldNrm);
                float3 V = normalize(_WorldSpaceCameraPos - i.worldPos);

                float ndotv = dot(N, V);

                // Sidedness gating
                if (_DoubleSided < 0.5)        // back faces only
                {
                    if (ndotv > 0) discard;
                }
                else if (_DoubleSided > 1.5)   // front faces only
                {
                    if (ndotv < 0) discard;
                }

                // Fresnel rim
                ndotv = saturate(abs(ndotv));  // abs for double-sided consistency
                float rim = pow(1.0 - ndotv, _RimPower);
                float3 rimCol = _RimColor.rgb * (rim * _RimStrength);

                // Full-surface overlay (set to black to disable)
                float3 fillCol = _OverlayColor.rgb;

                return float4(rimCol + fillCol, 1);
            }
            ENDCG
        }
    }

    Fallback Off
}

PBR_FresnelRim.shader

Shader "Custom/PBR_FresnelRim"
{
    Properties
    {
        _Color       ("Base Color", Color) = (1,1,1,1)
        _MainTex     ("Albedo (RGB) Alpha (A)", 2D) = "white" {}
        _Metallic    ("Metallic", Range(0,1)) = 0.0
        _Glossiness  ("Smoothness", Range(0,1)) = 0.5

        [NoScaleOffset]_BumpMap ("Normal Map", 2D) = "bump" {}
        _BumpScale   ("Normal Scale", Range(0,2)) = 1.0

        [HDR]_RimColor   ("Fresnel Edge Color (HDR)", Color) = (4,4,4,1)
        _RimPower    ("Fresnel Power (falloff)", Range(0.1, 8)) = 3.0
        _RimStrength ("Fresnel Strength (intensity)", Range(0, 10)) = 1.0
    }

    SubShader
    {
        Tags { "RenderType"="Opaque" "Queue"="Geometry" }
        LOD 300

        CGPROGRAM
        #pragma surface surf Standard fullforwardshadows
        #pragma target 3.0
        #pragma multi_compile_instancing

        sampler2D _MainTex;
        fixed4 _Color;
        half _Metallic;
        half _Glossiness;

        sampler2D _BumpMap;
        half _BumpScale;

        fixed4 _RimColor;
        half _RimPower;
        half _RimStrength;

        struct Input
        {
            float2 uv_MainTex;
            float2 uv_BumpMap;
            float3 worldPos;
            float3 viewDir;   // Unity provides world-space view direction
        };

        UNITY_INSTANCING_BUFFER_START(Props)
        UNITY_INSTANCING_BUFFER_END(Props)

        inline float3 UnpackNormalScaled(sampler2D nmap, float2 uv, float scale)
        {
            float3 n = UnpackNormal(tex2D(nmap, uv));
            n.xy *= scale;
            n = normalize(n);
            return n;
        }

        void surf (Input IN, inout SurfaceOutputStandard o)
        {
            fixed4 albedo = tex2D(_MainTex, IN.uv_MainTex) * _Color;
            o.Albedo     = albedo.rgb;
            o.Metallic   = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha      = albedo.a;

            // Normal mapping (optional)
            float3 N = float3(0,0,1);
            if (_BumpScale > 0.0001)
                N = UnpackNormalScaled(_BumpMap, IN.uv_BumpMap, _BumpScale);
            else
                N = normalize(o.Normal);

            // Fresnel rim: pow(1 - N·V, power)
            float3 V = normalize(IN.viewDir);
            float ndotv = saturate(dot(N, V));
            float rim   = pow(1.0 - ndotv, _RimPower);

            // Emission drives the glow; HDR color recommended
            o.Emission = _RimColor.rgb * rim * _RimStrength;
        }
        ENDCG
    }

    FallBack "Diffuse"
}