Occlude objects based on pre rendered zbuffer texture

Unity Engine
1

Hi, i am quite new in programming shaders so please bear with me.

I have a prerendered 360 fractal color + zbuffer texture.
My goal is to clip objects based on the fractal zbuffer.

It kinda works, but when I rotate the camera the position of the sphere shifts.

480×540 94.6 KB

I created the camera shader below to occlude the objects.
Could somebody please tell me what I am missing?

Many thanks!

Shader "Custom/CameraClipEffect"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _ZBufferTex("Texture", 2D) = "white" {}
        _ColorTex("Texture", 2D) = "white" {}
    }
    SubShader
    {
        // No culling or depth
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
           
            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }
           
            sampler2D _MainTex;
            sampler2D _CameraDepthTexture;
            sampler2D _ZBufferTex;
            sampler2D _ColorTex;
            fixed _DepthPower;

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 output;

                fixed4 colorCam = tex2D(_MainTex, i.uv);

                fixed4 zbufferTex = tex2D(_ZBufferTex, i.uv);
                zbufferTex = 1 - zbufferTex;
                fixed4 colorTex = tex2D(_ColorTex, i.uv);

                // get lineardepth value
                float d = UNITY_SAMPLE_DEPTH(tex2D(_CameraDepthTexture, i.uv));
                d = Linear01Depth(d);

                // compare depth value with zbuffer r channel
                if (d - zbufferTex.g < 0) {
                    output = colorCam;
                }
                else
                {
                    output = colorTex;
                }

                return output;
            }
            ENDCG
        }
    }
}
2

Instead of sampling the depth texture you could just render a sphere with a shader that has “Cull front” set in it that has ZWrite on and outputs the color you want. Then any shaders that do ZTesting (most of them), will be clipped past the outter of the sphere object. Set the render queue for the sphere very low, like “Background+1” so it renders before nearly everything else.