Unity - Depth Intersection Shader

IntersectionGlow.shader

Shader "Unlit/Intersection Glow"
{
	Properties
	{
		_Color ("Color", Color) = (1,0,0,1)
	}
	SubShader
	{
		Tags { "RenderType"="Transparent" "Queue"="Transparent" }
		LOD 100
		Blend One One // additive blending for a simple "glow" effect
		Cull Off // render backfaces as well
		ZWrite Off // don't write into the Z-buffer, this effect shouldn't block objects
		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag

			#include "UnityCG.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
			};

			struct v2f
			{
				float4 screenPos : TEXCOORD0;
				float4 vertex : SV_POSITION;
			};

			sampler2D _CameraDepthTexture; // automatically set up by Unity. Contains the scene's depth buffer
			fixed4 _Color;

			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
				o.screenPos = ComputeScreenPos(o.vertex);
				return o;
			}

			fixed4 frag (v2f i) : SV_Target
			{
				//Get the distance to the camera from the depth buffer for this point
                float sceneZ = LinearEyeDepth (tex2Dproj(_CameraDepthTexture, UNITY_PROJ_COORD(i.screenPos)).r);
                //Actual distance to the camera
                float fragZ = i.screenPos.z;

                //If the two are similar, then there is an object intersecting with our object
				float factor = 1-step( 0.1, abs(fragZ-sceneZ) );

				return factor * _Color;
			}
			ENDCG
		}
	}
}