Resolved Struggling to get custom fog to work with scene

Sorry for the awful title, but oh well. So, I have been working on a volumetric fog system for my project in URP, I have got the raymarching stuff set up and that all works, but I am now struggling to get this fog (which is being applied as a full-screen pass) to interact with the scene, it's currently behaving as though there was nothing there and it is just being pasted on top of it. I know why this is happening, and that's because I need to combine the depth textures, but I am struggling to find a way to do it. Here's the code:

Code (CSharp):

1. half sdScene(half3 p, half h)
2. {
3.     return p.y - h; // Signed distance field, kinda, i think...
4. }
5.  
6. inline void CalculateVolumeDensity_half(int samples, half maxDist, half3 rayOrigin, half3 rayDir, half height, out float accum)
7. {
8.     half stepSize = maxDist / half(samples);
9.  
10.     half d = 0.0; // Distance
11.     half a = 0.0; // Accumulation
12.     for(int i = 0; i < samples; i++)
13.     {
14.         half3 p = rayOrigin + rayDir * d; // Position
15.         half s = sdScene(p, height); // Distance to scene at any point.
16.  
17.         // Check if we are inside the fog (below the specified height value),
18.         // If we are, use a fixed step rate.
19.         if(s < 0.01)
20.         {
21.             d += stepSize;
22.             a += stepSize;
23.         }
24.         // If we are not inside the fog, but still in range, use Spheretracing.
25.         else if(s >= 0.01 && d < maxDist)
26.         {
27.             d += s;
28.         }
29.         // If we are outside of the fog's range, just break out of the loop.
30.         else
31.         {
32.             break;
33.         }
34.     }
35.     //return the accumulated fog.
36.     accum = a;
37. }

Thank you to anyone who is able to help, and sorry for wording this whole thing poorly.

 

After messing around in Shadertoy, I have figured out how to fix this. For anyone wondering, I just have to check if the fog's distance is greater than or equal to the Unity scene's distance.