GrabPass and _GrabTexture do not work on Android devices?

For my current project I wrote a fixed shader program that makes use of GrabPass{} and _GrabTexture.

This all works fine in the editor with OpenGL ES 1.x/2.0 emulation, but as soon as I run this on an Android device, it is interpreted as if _GrabTexture is a black source. The question is whether or not I am doing something wrong, it is not supported by Unity but it is never documented, or did I encounter a bug. Is there anyone who has used this successfully?

The following shader illustrates the issue:

Code (csharp):

1.  
2. Shader "FailingShader" {
3.  
4.     Properties {
5.         _Color ("Color", Color) = (1,1,1,1)
6.         _MainTex("Main Texture", 2D) = "white" {}
7.     }
8.  
9.     Category {
10.         Tags {"RenderType"="Opaque"}
11.        
12.         SubShader {
13.             Pass {
14.                 Name "BASE"
15.                 Lighting On
16.                 SeparateSpecular On
17.                 Material {
18.                     Diffuse [_Color]
19.                     Ambient [_Color]
20.                 }
21.             }
22.            
23.             GrabPass {  }
24.            
25.             Pass {
26.                
27.                 SetTexture [_MainTex] {
28.                 }
29.                
30.                 SetTexture [_GrabTexture] {
31.                     Combine texture + previous
32.                 }
33.             }
34.         }
35.        
36.         SubShader {
37.             Pass {
38.                 Name "BASE"
39.                 Lighting On
40.                 SeparateSpecular On
41.                 Material {
42.                     Diffuse [_Color]
43.                     Ambient [_Color]
44.                 }
45.             }
46.         }
47.     }
48. }
49.  

Strange thing is that it will never end up in the fallback shader, so somehow the first shader always succeeds.

Any help would be highly appreciated!

 

Still any help is very much appreciated. Just found out that on Android 3 the behavior is even more strange. It seems like it is parts of the screen that was visible before starting Unity.
Hope someone is able to clarify something regarding this, or will I have better luck at the shaders forum?

 

Not sure what is going on but I am having the same issue here. GrabPass works fine on Windows but not on Android. I am pretty sure Android GLES 2.0 devices can handle GrabPass, which is basically a render target that is provided to the shader. I am thinking this is probably a bug in Unity than anything else. Unity guys can you verify that?

 

Any updates on this issue? Having similar problem on Tegra 2, GrabPass randomly picks a texture from VRAM intead of the framebuffer. I believe GrabPass doesn't work at all so what was left in the GPU register during last draw call is returned.

 

Hello,

Is there any update on this ? We are having the exact same issue, the shader grabpass not working on Tegra2 devices, can someone confirm if that is fixable or will be fixed ? Any workaround ? Also, apparently We must set the color buffer must be set to 32 bits in order to get the "default asset" image effect script running on Android which I am not sure if it is intended or not.

 

Hey all, same issue here. I'm currently using Unity 3.5. Unity guys, would love a comment on this.
Thanks

 

Out of curiosity did you try this variation:

GrabPass { "TextureName" }

 

I would also want to know this. I can't make it to work on Android devices.

 

This issue still seems to be there with Unity 4.3. It seems to work when using OpenGL ES 3.0 but not with 2.0. Some definite response from the Unity devs would be very helpful here. Is GrabPass supported with OpenGL ES 2 on Android? And if so, how to make it work?

 

I'd like to bump this thread - I'm attempting to use a Blur shader on Android, specifically a Galaxy Note 10.1, under Unity Pro 4.3.4 and if GrabPass is defined in the shader without a trivial fallback you get the dreaded "No subshaders can run on this graphics card.". I've tried using Open ES 2.0 and 3.0 without luck.

Nevermind the wisdom of using a blur shader on Android. That's my business!

A response on this issue from Unity would be sincerely appreciated.

Thanks,
Mike.

 

Same here. And while it works with OpenGL ES 3.0, it is buggy - the image differs from what I get on PC, also, it doesn't takes the device orientation into account.

 

Any suggestion for this issue? I'm trying to use GrabTexture effect on Asus Transformer Prime TF201 (GPU Nvidia Tegra 3), with no luck yet.

 

same here, got unusable crazy colours.
have submitted a bug.

 

You can try changing the tags line from

Code (CSharp):

1. Tags {"RenderType"="Opaque"}

to

Code (CSharp):

1. Tags { "Queue"="Transparent+1" "RenderType"="Opaque" }

basically, this makes the GrabPass happen when almost everything has been rendered in one frame, rather than grabbing nothing when everything is not rendered yet.

 

I know its old thread, but I'm still having the same issue with Unity 2018.3 , does anyone found a solution for this issue?

 

Still having this issue, and **very** dependent on a grabpass blur in my project.

 

Still looking for a solution to this. Are there really no unity team around who know the answer?

 

It works in Multi-pass stereo VR, but not in Single-Pass stereo VR.

 

This is a active issue, same for depth texture rendering.
https://issuetracker.unity3d.com/is...ering-when-using-single-pass-stereo-rendering
https://issuetracker.unity3d.com/is...th-vr-single-pass-sampling-cameradepthtexture

 

I have the same problem with Unity 2019.2.17. Disabling of "Use 32-bit Display Buffer" helps and shaders start to work correctly, but after this disabling I've got some color's artefacts and bandings, so I'm still looking for the appropriate way to resolve this issue.