Question AR Occlusion Environment + ARPlane Flickering. How to fix it ?

Hi,

im currently using the AR Plane Manager to show the shadow of my object and would love to use the AR Occlusion environment but because of the depth the ARPlane keep flicker as its logically at an equal depth..

Any clues on how to fix this ?
I was thinking to 2 ways :
- force the ARPlane to be y+0.01 to fix some problem
- not apply the Environment Occlusion to the ARPlane, but not sure how we can exclude it.

Thanks in advance.

 

I have the same problem and I can't find any solution. Hope for an answer. Thanks

 

This problem is called Z-Fighting and the common solution is to write a custom shader with the Offset command.
Here are two great videos about Z-Fighting.
http://answers.unity.com/answers/51144/view.html

I took the FeatheredPlaneShader from AR Foundation Samples and added an Offset command to it. While typically Z-Fighting can be fixed by adding Offset -1, -1, I only managed to get it working with ARKit by setting factor and scale to -50.

Here is the resulted shader.

Spoiler: shader

Code (CSharp):

1. Shader "Unlit/FeatheredPlaneShader"
2. {
3.     Properties
4.     {
5.         _MainTex ("Texture", 2D) = "white" {}
6.         _TexTintColor("Texture Tint Color", Color) = (1,1,1,1)
7.         _PlaneColor("Plane Color", Color) = (1,1,1,1)
8.     }
9.     SubShader
10.     {
11.         Tags { "RenderType"="Transparent" "Queue"="Transparent" }
12.         LOD 100
13.         Blend SrcAlpha OneMinusSrcAlpha
14.         ZWrite Off
15.         Offset -50, -50
16.  
17.         Pass
18.         {
19.             CGPROGRAM
20.             #pragma vertex vert
21.             #pragma fragment frag
22.          
23.             #include "UnityCG.cginc"
24.  
25.             struct appdata
26.             {
27.                 float4 vertex : POSITION;
28.                 float2 uv : TEXCOORD0;
29.                 float3 uv2 : TEXCOORD1;
30.             };
31.  
32.             struct v2f
33.             {
34.                 float4 vertex : SV_POSITION;
35.                 float2 uv : TEXCOORD0;
36.                 float3 uv2 : TEXCOORD1;
37.             };
38.  
39.             sampler2D _MainTex;
40.             float4 _MainTex_ST;
41.             fixed4 _TexTintColor;
42.             fixed4 _PlaneColor;
43.             float _ShortestUVMapping;
44.  
45.             v2f vert (appdata v)
46.             {
47.                 v2f o;
48.                 o.vertex = UnityObjectToClipPos(v.vertex);
49.                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
50.                 o.uv2 = v.uv2;
51.                 return o;
52.             }
53.          
54.             fixed4 frag (v2f i) : SV_Target
55.             {
56.                 //return 1;
57.                 fixed4 col = tex2D(_MainTex, i.uv) * _TexTintColor;
58.                 col = lerp( _PlaneColor, col, col.a);
59.                 // Fade out from as we pass the edge.
60.                 // uv2.x stores a mapped UV that will be "1" at the beginning of the feathering.
61.                 // We fade until we reach at the edge of the shortest UV mapping.
62.                 // This is the remmaped UV value at the vertex.
63.                 // We choose the shorted one so that ll edges will fade out completely.
64.                 // See ARFeatheredPlaneMeshVisualizer.cs for more details.
65.                 col.a *=  1-smoothstep(1, _ShortestUVMapping, i.uv2.x);
66.                 return col;
67.             }
68.             ENDCG
69.         }
70.     }
71. }
72.  

 

I tried to force the ARPlane to be at an higher y. In the ARPlaneManager script, add two lines of code.

Code (CSharp):

1.         protected override void OnAfterSetSessionRelativeData(
2.             ARPlane plane,
3.             BoundedPlane sessionRelativeData)
4.         {
5.             ARPlane subsumedByPlane;
6.             if (m_Trackables.TryGetValue(sessionRelativeData.subsumedById, out subsumedByPlane))
7.             {
8.                 plane.subsumedBy = subsumedByPlane;
9.             }
10.             else
11.             {
12.                 plane.subsumedBy = null;
13.             }
14.             // Here is the workaround
15.             Vector3 temp = new Vector3(0.0f, 0.01f, 0.0f);
16.             plane.transform.position += temp;
17.             // End workaroud
18.             plane.UpdateBoundary(subsystem);
19.         }

You can do the same using translation.
Now the floor no more flickers, but i think this could not be the solution... it's only a workaround.

 

Thanks the Offset in my differents ground shaders made the tricks ! <3

 

Hi, I just tested the environment occlusion with iPhone 12 Pro, and I noticed this problem. The texture I gave to the tracked planes flickers, but also the shadows of my instantiated objects.
I tried to modify the FeatheredPlaneShader but I noticed no difference. Could you explain me your solution? Thanks!

 

Hi, I just added the Offset in my shader
Check the video above for more details explanation!

Best,
D

 

I added an offset to my shaders, but if the offset is small it continues to flicker, if is high the occlusion doesn't work.

 

For anyone using Shader Graph and willing to use the Offset method told by @KirillKuzyk to fix the z fight problem with AR occlusion, such as on the BlurredShadowPlane shader available here, you can add to the Position Input of the PBR Master, the following fix from @bgolus instead of "Object Position".
I personally set the offset property to 0.06 but you might want to experiment on that one.

 

Hey can you provide the shader after making the adjustments?

 

Moving offset to -50,-50 works fine but this comes with a problem. I'm having a plane at (0,0) then I'm adding a model with it's base point at (0,0) and it seems that the plane cuts into the model proportional with the offset value and this is ugly. Any idea how we can fix this?

 

Agreed. I have the same problem. Offset just makes the problem move up. We really kind of want the detected ground plane not to be considered part of the occlusion. If we could set the ground level in the AR Occlusion control based on where user places object or something it would work. Or the occlusion planes that are horizontal should be able to be pushed back a bit. 0.01 or such.

 

What would be helpful is to have access to the material/shader used to draw the Z buffer for the occlusion. We could make that a shadow catcher so that at least we get stable shadows on it.

 

Has anyone found a solution for this? In my case the shadows we are rendering on the floor get occluded. I tried moving things up a bit, but the amount I have to move up for it to stop occluding the shadows is too high that they don't look like they're on the floor anymore

 

I would also like to know if anyone has a solution for this issue.