The scriptable render pipeline how to support GrabPass?

I am write a custom SRP, but the game view can not deal with GrabPass. How can I fix it?
The unity report the error:

Shader properties can't be added to this global property sheet. Trying to add _Refraction (type 3 count 1)

UnityEngine.Experimental.Rendering.ScriptableRenderContext:Submit()

Game.MobileRenderPipeline:Render(ScriptableRenderContext, Camera[]) (at Assets/Game/Scripts/Rendering/MobileRenderPipeline.cs:224)

UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

 

BTW, I test grab pass on LightWeightRenderPipeline, it report the same error:

Shader properties can't be added to this global property sheet. Trying to add _Refraction (type 3 count 1)

UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

And the LightWeightRenderPipeline seems has compile error for Unity 2018.1.0b9.

 

Stumbled upon this thread because I wanted to learn more after seeing:

Source: https://blogs.unity3d.com/2018/03/16/the-high-definition-render-pipeline-focused-on-visual-quality/

Beyond that, this thread is the only mention I could find of Grabpass in relation to the HDRP.

I wonder if the intention is just for users to explicitly write to render targets and sample those in shaders instead? Can anyone clarify?

 

@phil_lira, I am working on my own SRP and try to render the opaque to a render texture when there has any object after camera culled with the material that require the opaque texture. How can I check this, I don't want to render the opaque texture when there have no any renderer in the cull set require the grabpass.

 

This might help:

https://forum.unity.com/threads/graphics-blit-vs-grabpass-vs-rendertexture.523825/

Talks about 2 other ways to do same as grabpass

 

Any update on this?

 

Thanks! Keep up the good work.

So is it implemented as a global "GrabPass" texture available after opaque objects have been rendered? What's the uniform name?

 

Wait is legacy GrabPass contain transparent objects?

 

Just a suggestion for this as we've already implemented this in our local branch of SRP, but the ability to choose the grab pass to be downsampled could be helpful for performance and straight-forward to implement.

 

Hi,
will we see this soon?

 

Hi Andre,
Can _CameraOpaqueTexture be accessed via shader graph?
Also I'm writing a shader using this (via lightweight render pipeline) and I'm finding the _CameraOpaqueTexture is only grabbing geometry. Is it possible to grab what the camera sees? Such as sprites and particles?
I am in a 2D project at the moment.

 

I notice _CameraOpaqueTexture is in the 2.0.0-preview changelog on Github but the latest version in the package manager is 1.1.4.

1. Any ETA on this being released to preview on the package manager?
2. Is it reasonably safe to grab the github version for a project that is still in the prototype stage?
3. Is this backwards compatible to 2018.1.x or do we need to be using 2018.2?

 

@Tim-C Would you mind providing detail on how one can go about mapping the _CameraOpaqueTexture correctly onto a mesh as if to mimic a grab pass (namely, the graphics rendered behind the mesh are rendered in the correct location(s) on the mesh).

I have been able to access the texture but I can't work out how to correctly position it on the object. Any help would be greatly appreciated, as I am also trying to create a water shader similar to the one made (in the shader graph) here . Many thanks in advance!

 

Awesome - thankyou!!!

 

Are there any plans to make command buffers executable at an integer queue rather than the predefined list of enums? Right now it's really hard/impossible to get a command buffer to execute before a custom shader. Will SRP solve this problem?

 

this is GREAT news, will test that camera opaque texture asap.
Amazing that downsampling options are included.

 

Hey Grab Pass folks!

To access

_CameraOpaqueTexture

you must first enable it in the LWRP Asset. There are also some options for different Downsampling qualities.



To access it in Shader Graph; you can then create a Texture Property, and then use

_CameraOpaqueTexture

in the reference field. You will also have to disable the Texture Property from being exposed, otherwise this will likely be overriden by the Material Inspector.

Once the Property is Samples using the 'Sample Texture 2D' node, you can use it for GrabPass-like effects!

Here is a really simple Shader Graph setup:



Which, when applied to this 'screen' will cause a repeated sample (Im applying it to a primitive quad so the camera texture will stretch to fill the mesh):



However, you can also use the Screen Position Node in Shader Graph, so that instead of drawing the whole camera onto the mesh, you instead remap the UV used by the texture for what area of the screen the mesh 'uses':



Which will result in being able to see objects on the side of the screen (In this case; a barrel). It is important to note that you currently have to switch the Shader to 'Transparent' so that it is drawn after Opaque Pass.


And then you can use all kinds of effects, in Shader Graph, on the camera texture:



Including Noise Distortion (One of the most common uses for Grab Pass; especially for particle explosions!):





It is also possible to get the

_CameraDepthTexture

aswell; Just enable Depth Texture on the LWRP Asset and use

_CameraDepthTexture

for the Texture Property reference.



AFAIK; all of this works in the same way if you were writing shaders for LWRP, instead of using Shader Graph.

 

Hey Andy, Thanks for keeping us updated! It's great news, though I'm more interested in a way to also grab transparent passes; is this still impossible to achieve with the SRP?

 

https://github.com/UnityTechnologies/LWRPScriptableRenderPass_ExampleLibrary

In DemoScene_ScreenEffect; you should be able to modify the example(s) with Felipe's suggestions.

 

Wow, didn't know it's already implemented. Super nice feature, thank you guys!

 

Is there a way to grab the screen at any time though? _CameraOpaqueTexture still won't contain transparent objects right? Either way I can't see how this could handle transparent objects both behind and in front of the effect - not even simultaneously, just in general.

 

Implement IAfterTransparent and IAfterOpaque both?

 

Hi, Andy. I try to follow the sample project and grab the screen like the ScreenEffectPass do. But it's not work in my project even thought I copy and paste the ScreenEffectPass.cs into my repository. I've added this script to my main camera and saw the tag in Profiler view. Seems the script is working, but the _GrabTexture is always a grey texture unlike the sample's. I'm wondering if I missed some configuration steps to make it work.

By the way, I just enabled the LWRP and Shader Graph packages in my project. Do you have any idea about this? Thank you.

 

Seems I must enter the Play mode to get the correct result. After I remove and add the script to camera several times, it works correctly. Still have no idea about this issue.

 

Hi, I just changed Pass on 'IAfterTransparentPass' in your script and it looks like this in Play Mode. What do you think?

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.Experimental.Rendering;
5. using UnityEngine.Experimental.Rendering.LightweightPipeline;
6. using UnityEngine.Rendering;
7.  
8. [ExecuteInEditMode]
9. [ImageEffectAllowedInSceneView]
10. public class ScreenEffectPass : MonoBehaviour, IAfterTransparentPass
11. {
12.  
13.     private ScreenEffectPassImpl m_grabPass;
14.  
15.     public ScriptableRenderPass GetPassToEnqueue(RenderTextureDescriptor baseDescriptor, RenderTargetHandle colorHandle, RenderTargetHandle depthHandle)
16.     {
17.         if (m_grabPass == null)
18.             m_grabPass = new ScreenEffectPassImpl(colorHandle);
19.  
20.         return m_grabPass;
21.     }
22.  
23. }
24.  
25.  
26. public class ScreenEffectPassImpl : ScriptableRenderPass
27. {
28.     const string k_RenderGrabPassTag = "Screen Effect Pass";
29.  
30.  
31.     private RenderTextureDescriptor m_BaseDescriptor;
32.     private RenderTargetHandle m_ColorHandle;
33.  
34.     public ScreenEffectPassImpl(RenderTargetHandle colorHandle)
35.     {
36.         m_ColorHandle = colorHandle;
37.     }
38.  
39.     public override void Execute(ScriptableRenderer renderer, ScriptableRenderContext context, ref RenderingData renderingData)
40.     {
41.         CommandBuffer buf = CommandBufferPool.Get(k_RenderGrabPassTag);
42.  
43.         using (new ProfilingSample(buf, k_RenderGrabPassTag))
44.         {
45.            
46.             // copy screen into temporary RT
47.             int screenCopyID = Shader.PropertyToID("_ScreenCopyTexture");
48.             RenderTextureDescriptor opaqueDesc = ScriptableRenderer.CreateRenderTextureDescriptor(ref renderingData.cameraData);
49.             buf.GetTemporaryRT(screenCopyID, opaqueDesc, FilterMode.Bilinear);
50.             buf.Blit(m_ColorHandle.Identifier(), screenCopyID);
51.  
52.  
53.  
54.             //Set Texture for Shader Graph
55.             buf.SetGlobalTexture("_GrabTexture", screenCopyID);
56.         }
57.  
58.         context.ExecuteCommandBuffer(buf);
59.         CommandBufferPool.Release(buf);
60.     }
61. }
62.  

 

Hi Andy,
It looks like the blur shader in this example doesn't work as expected on LWRP v4.9.0.
It leaves 'trails', or should I say, a feed-back loop is created.

 

Hey there! when I try to implement this method it only ever uses the scene view camera and not the game camera, even in play mode after being built! is there any way to fix this? otherwise it is just grey when built.

 

Just trying this out, works fine in the editor, but doesn't seem to work on my galaxy s8 (android). any ideas?

Also I have the rendering API set to gles 3.0

 

Okay, so the shader works on meshes, etc in the editor and device (android). Just not on UI objects on android. Any ideas?

 

How can I use this like a full screen post process effect. I mean as you showed we can make a shader in Shadergraph which has some camera effect like blur, UV distort, etc. But how can I use this shader for a full screen camera effect? With a second camera? Any suggestion?

 

small question,

It's been noted above that it's possible to generate textures after the opaque and transparent render pass; IAfterTransparent and IAfterOpaque. Though my question is whether it's possible to design and implement custom render pass lists?

My game is from a fixed camera perspective, so I thought it may be possible group certain meshes into render passes based on their respective distance from the camera, allowing me to simulate _Grabpass. Currently, the light-weight render pipeline supports a single Opaque Pass, how possible would be to create additional opaque passes?


My only concern is that I'm pretty new to this, and have no knowledge about setting this up.

 

You could make a screen sized quad and stick it directly in front of the camera so that it takes up the entire screen

 

Seems like the API has changed quite a bit, as https://github.com/UnityTechnologies/LWRPScriptableRenderPass_ExampleLibrary no longer works with Unity 2019.1. Any chance it can be updated or are there any other examples on using scriptable render passes?

@phil_lira @Andy-Touch @Andre_Mcgrail

 

Grab pass sure was convenient, and it allowed capturing the screen at an arbitrary shader render queue, something the new scriptable render pipelines can't do... hope it will come back for SRP.

 

Completely agree. While scriptable render passes allow to grab the camera texture once at specific points (before/after opaque/transparent, etc), there are still situations when we need to perform the grab multiple times per frame before executing specific shaders (eg, one of my asset store packages depends on this and it has quite a lot of users). Afaik, neither LWRP nor HDRP allows this by design. Considering the plans of replacing current render system with SRP, this looks troublesome...

Would really love to hear any comments on this situation from the Unity stuff @phil_lira @Andy-Touch @Andre_Mcgrail

 

I also don't like having to use command buffers. It seems like a System.Action or something similar would be better and just simply use Graphics.* to do the work. This would allow more complex rendering code and would have access to the latest and up to date script variables, texture references, etc. without having to re-create or setup a command buffer every frame.

 

So, LWRP is now "stable" and users are widely adopting it, but... It's impossible to implement some of the effects, that were using GrabPass on the old rendering system. I'm talking about situations when we were able to grab screen texture before executing a shader pass, which allowed to "stack" multiple effects. Afaik, it's not possible at all with the LWRP. (or am I missing something?)

Here is a thread that touches the same subject, but again, without a solution: https://forum.unity.com/threads/srp-and-grabpass-with-transparent.555892/

@phil_lira @Andy-Touch @Andre_Mcgrail @Tim-C

 

Not out of the box without writing your own forked version of LWRP pipeline.

 

Which is impossible, as I need that for an Asset Store package, which should support the built-in SRPs.