Shader access to shadow map

Hello

I'm writing some post process effects/shaders, and I need read acess to the shadow map texture.

Has unity some built-in access to the shadow map texture, or I have to write my own procedure (i.e, render scene from light point of view)?

I've seen that UnityCG.cginc has a sampler2D called _ShadowMapTexture, but is seems to be empty in my initial tests.

Thanks in advance

 

Thanks

 

@Aras: Is it in general possible to access the shadow map (the depth value) inside the fragment shader of a regular (forward rendering) shader?

 

I'm just posting this here , just in case someone stumbles across the same question! So I was also searching for a way to sample the screen space shadow texture with a commandbuffer and noticed, that they use this technique in the 3D GameKit from Unity! And it just seems to work straight out of the box this way! I saw many questions about this and nobody ever posted his working code, so here ya go!

Code that should be attached to the main directional light:

Code (CSharp):

1. using UnityEditor;
2. using UnityEngine;
3. using UnityEngine.Rendering;
4.  
5. namespace Gamekit3D
6. {
7.     [ExecuteInEditMode]
8.     public class CopyShadowMap : MonoBehaviour
9.     {
10.         CommandBuffer cb = null;
11.  
12.         void OnEnable()
13.         {
14.             var light = GetComponent<Light>();
15.             if (light)
16.             {
17.                 cb = new CommandBuffer();
18.                 cb.name = "CopyShadowMap";
19.                 cb.SetGlobalTexture("_DirectionalShadowMask", new RenderTargetIdentifier(BuiltinRenderTextureType.CurrentActive));
20.                 light.AddCommandBuffer(UnityEngine.Rendering.LightEvent.AfterScreenspaceMask, cb);
21.             }
22.         }
23.  
24.         void OnDisable()
25.         {
26.             var light = GetComponent<Light>();
27.             if (light)
28.             {
29.                 light.RemoveCommandBuffer(UnityEngine.Rendering.LightEvent.AfterScreenspaceMask, cb);
30.             }
31.         }
32.     }
33. }

And in the shader, access the map likes this:

Code (CSharp):

1. sampler2D _DirectionalShadowMask;

and in the surf/fragment shader:

Code (CSharp):

1. float shadowmask = tex2D(_DirectionalShadowMask,screenUV).b;

Theres also this Macro written there, but I'm not sure for what it's used:

Code (CSharp):

1. UNITY_DECLARE_SHADOWMAP(_DirectionalShadowMap);

(I just didnt used it and it still worked) UPDATE: Also thanks to @bgolus for clearing this up:
That's for defining a shadow map texture object ... which technically the screen space shadow texture is not so can be ignored. You've already defined it as a sampler2D, which is what it is.

Anyways, I hope this helps someone!