How can I get Z-depth from unlit shader? - unity3d

Question

Currently, I try to make z depth effect as Image Effect, but result image is not correctly rendered. something wrong...
If I use standard shader (unity 5), result image was correctly rendered(z depth image is ok), but not unlit shader.
what happen? if you have any idea, tell me why.
shader
Shader "Custom/RenderDepth"
{
Properties
{
_DepthLevel ("Depth Level", Range(1, 3)) = 2
}
SubShader
{
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
uniform sampler2D_float _CameraDepthTexture;
uniform fixed _DepthLevel;
uniform half4 _MainTex_TexelSize;
struct uinput
{
float4 pos : POSITION;
half2 uv : TEXCOORD0;
};
struct uoutput
{
float4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
};
uoutput vert(uinput i)
{
uoutput o;
o.pos = mul(UNITY_MATRIX_MVP, i.pos);
o.uv = MultiplyUV(UNITY_MATRIX_TEXTURE0, i.uv);
return o;
}
fixed4 frag(uoutput o) : COLOR
{
float depth = UNITY_SAMPLE_DEPTH(tex2D(_CameraDepthTexture, o.uv));
depth = pow(Linear01Depth(depth), _DepthLevel);
return depth;
}
ENDCG
}
}
}
CS
using UnityEngine;
using System.Collections;
[ExecuteInEditMode]
[RequireComponent (typeof(Camera))]
public class Test : MonoBehaviour
{
public Camera _cam;
public Material mat;
public float DepthLevel = 1.0F;
void Start ()
{
_cam.depthTextureMode |= DepthTextureMode.Depth;
}
void Update ()
{
}
void OnRenderImage (RenderTexture source, RenderTexture destination)
{
mat.SetFloat("_DepthLevel", DepthLevel);
Graphics.Blit(source, destination, mat);
}
}

Answer 1

I've found this solution. I use the SHADOWCASTER pass from the VertexLit legacy shader prior to render my unlit object.
Then your shader would look like this:
Shader "Custom/RenderDepth"
{
Properties
{
_DepthLevel ("Depth Level", Range(1, 3)) = 2
}
SubShader
{
UsePass "Legacy Shaders/VertexLit/SHADOWCASTER"
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
uniform sampler2D_float _CameraDepthTexture;
uniform fixed _DepthLevel;
uniform half4 _MainTex_TexelSize;
struct uinput
{
float4 pos : POSITION;
half2 uv : TEXCOORD0;
};
struct uoutput
{
float4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
};
uoutput vert(uinput i)
{
uoutput o;
o.pos = mul(UNITY_MATRIX_MVP, i.pos);
o.uv = MultiplyUV(UNITY_MATRIX_TEXTURE0, i.uv);
return o;
}
fixed4 frag(uoutput o) : COLOR
{
float depth = UNITY_SAMPLE_DEPTH(tex2D(_CameraDepthTexture, o.uv));
depth = pow(Linear01Depth(depth), _DepthLevel);
return depth;
}
ENDCG
}
}
}

Answer 2

You need to provide a fallback option in the unlit shader so it can use the other needed passes (depth/shadow/etc) from this fallback shader.
Adding the following line to your unlit shader should help.
Fallback "Diffuse"