Would I need a Custom Shader?

Is it possible to render a reflection probe’s data onto an invisible object in the scene?

What I want to accomplish: I have a real photograph and I am working with forced perspective to create a 2.5D environment. In this image I have a reflective surface. I would like to cast reflections onto an invisible plane and position in between the camera and the image to give the illusion of the 2D image having reflection when a 3D character walks by it. But the plane must be invisible, rendering only the reflection probe data. I guess this would be similar to casting “Shadows Only?”

Ive attached a picture to help explain. I want to have only Ethan’s reflection rendered and not the plane its reflecting on.

Hope I described that clearly and thanks in advance so much for any help

Shader “Reflection” {
Properties {
_Tint (“Tint”, Color) = (1,1,1,1)

    SubShader {
        Tags { "Queue"="Transparent" }

        Pass {
            Blend SrcAlpha OneMinusSrcAlpha
            ZWrite Off
            #pragma vertex vert
            #pragma fragment frag
            #pragma target 3.0
            #include "UnityCG.cginc"

            fixed4 _Tint;

            struct v2f {
                float4 pos : SV_POSITION;
                float3 worldNorm : TEXCOORD0;
                float3 viewDir : TEXCOORD1;

            v2f vert (appdata_full v) {
                v2f o;
                o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
                o.worldNorm = UnityObjectToWorldNormal (v.normal);
                float3 worldPos = mul (unity_Object2World, v.vertex);
                o.viewDir = normalize (worldPos - _WorldSpaceCameraPos);
                return o;

            half4 frag (v2f i) : SV_Target
                float3 worldRefl = reflect (i.worldNorm, -i.viewDir);
                half4 refl = UNITY_SAMPLE_TEXCUBE (unity_SpecCube0, worldRefl) * _Tint;
                return refl;

Something like that is how you would go about it, although I’m not entirely sure you can get the alpha value of a reflection probe. Try it with the probe set to ‘Depth Only’ or something like that, only rendering the player object.