Render different texture for each eye with single-pass pipeline?

I just need to render an unlit transparent quad, but with a different texture for each eye.

I suspect this is possible with a custom shader. Does anybody have such a beast lying around? Or even know whether it is possible?

(I'm targeting Oculus Go, if it matters.)

 

Hi,
You need to look here : https://docs.unity3d.com/Manual/SinglePassStereoRendering.html

You can just check the unity_StereoEyeIndex variable. unity_StereoEyeIndex is exposed in Shaders, so eye-dependent calculations can be performed. The value of unity_StereoEyeIndex is 0 for rendering of the left eye, and 1 for rendering of the right eye.

This shader should work for unlit objects :

Code (CSharp):

1. Shader "Custom/Unlit/StereoTwoTextures"
2. {
3.     Properties
4.     {
5.         _LeftTex ("Left texture", 2D) = "white" {}
6.         _RightTex ("Right texture", 2D) = "white" {}
7.     }
8.     SubShader
9.     {
10.         Tags { "RenderType"="Opaque" }
11.         LOD 100
12.  
13.         Pass
14.         {
15.             CGPROGRAM
16.             #pragma vertex vert
17.             #pragma fragment frag
18.             // make fog work
19.             #pragma multi_compile_fog
20.        
21.             #include "UnityCG.cginc"
22.  
23.             struct appdata
24.             {
25.                 float4 vertex : POSITION;
26.                 float2 uv : TEXCOORD0;
27.             };
28.  
29.             struct v2f
30.             {
31.                 float2 uv : TEXCOORD0;
32.                 float2 uv1 : TEXCOORD1;
33.                 UNITY_FOG_COORDS(1)
34.                 float4 vertex : SV_POSITION;
35.             };
36.  
37.             sampler2D _LeftTex;
38.             float4 _LeftTex_ST;
39.  
40.             sampler2D _RightTex;
41.             float4 _RightTex_ST;
42.                    
43.             v2f vert (appdata v)
44.             {
45.                 v2f o;
46.                 o.vertex = UnityObjectToClipPos(v.vertex);
47.                 o.uv = TRANSFORM_TEX(v.uv, _LeftTex);
48.                 o.uv1 = TRANSFORM_TEX(v.uv, _RightTex);
49.                 UNITY_TRANSFER_FOG(o,o.vertex);
50.                 return o;
51.             }
52.        
53.             fixed4 frag (v2f i) : SV_Target
54.             {
55.                 // sample the texture
56.                 fixed4 col;
57.                 fixed4 l = tex2D(_LeftTex, i.uv);
58.                 fixed4 r = tex2D(_RightTex, i.uv1);
59.  
60.                 col = r * unity_StereoEyeIndex + l * (1 - unity_StereoEyeIndex);
61.  
62.                 // apply fog
63.                 UNITY_APPLY_FOG(i.fogCoord, col);
64.                 return col;
65.             }
66.             ENDCG
67.         }
68.     }
69. }
70.  

 

Thank you, that looks like just what I need! To avoid the branch, could we change lines 60-69 to something like:

Code (csharp):

1.     col = r * unity_StereoEyeIndex + l * (1 - unity_StereoEyeIndex);

?

 

Indeed, fixed it

 

Hi there! Unfortunately, I can see the texture only through the Left eye. The right eye shows nothing. Any ideas on how to fix this?

 

I have searched a lot on the internet. I can save you time. One day as of this post Unity offers absolutely nothing to get a single render texture with stereoscopic view using Single Instance.

But of course, there is the issue that if you want to make a relatively complex game Single Instance is practically mandatory.

The only solution I have found is also quite simple: use two cameras for each of the eyes of the HMD viewer. So, for each stereoscopic texture that we want, for example a portal, we will have to create two cameras that will track the position of the eyes in a relative way, recording the texture in two render textures that we can assign to each of the textures of a shader that unify in a single vision.

 

Are you able to make unity render two cameras in headset? I've tested and each time the second camera in the hierarchy is just static or won't load/hangs on unity loading screen.

 

This still works if you get the value in the vertex shader. See this post: