Cannot get very basic Camera.SetTargetBuffers to render anything

I'm trying to use Camera.SetTargetBuffers to render to multiple render targets at once (MRT).

I created a very basic setup to test it in a minimal case, but nothing renders to the target buffers according to the frame debugger.

First, the camera setup. Note that, as recommended by my research to get STB to work, I use the forward rendering path:



Next, I added a small component to the camera to call STB on start:


The script is very barebones:

Code (CSharp):

1. using UnityEngine;
2.  
3. public class MrtTest : MonoBehaviour
4. {
5.     public int renderTargetCount = 4;
6.  
7.     public RenderTexture[] colorTextures;
8.  
9.     public RenderTexture depthTexture;
10.  
11.     private new Camera camera => GetComponent<Camera>();
12.  
13.     void Start()
14.     {
15.         colorTextures = new RenderTexture[renderTargetCount];
16.         var colorBuffers = new RenderBuffer[renderTargetCount];
17.  
18.         depthTexture = new RenderTexture
19.         (
20.             camera.pixelWidth,
21.             camera.pixelHeight,
22.             24,
23.             RenderTextureFormat.Depth
24.         )
25.         {
26.             name = "DepthCustom",
27.             hideFlags = HideFlags.HideAndDontSave
28.         };
29.  
30.         for (var i = 0; i < colorTextures.Length; i++)
31.         {
32.             colorTextures[i] = new RenderTexture
33.             (
34.                 camera.pixelWidth,
35.                 camera.pixelHeight,
36.                 0,
37.                 RenderTextureFormat.ARGB32
38.             )
39.             {
40.                 name = "ColorCustom" + i,
41.                 hideFlags = HideFlags.HideAndDontSave
42.             };
43.  
44.             colorBuffers[i] = colorTextures[i].colorBuffer;
45.         }
46.  
47.         camera.SetTargetBuffers(colorBuffers, depthTexture.depthBuffer);
48.     }
49. }

Next, I created a shader and material which I'm rendering on a 3 cubes in the scene:

Again, the shader is as barebones as it gets. It should output red to the first RT, green to the second RT, then blue, then yellow.

Code (CSharp):

1. Shader "Test/MRT"
2. {
3.     SubShader
4.     {
5.         Pass
6.         {
7.             CGPROGRAM
8.  
9.             #pragma vertex vert
10.             #pragma fragment frag
11.             #include "UnityCG.cginc"
12.  
13.             struct appdata
14.             {
15.                 float4 vertex : POSITION;
16.             };
17.  
18.             struct v2f
19.             {
20.                 float4 vertex : SV_POSITION;
21.             };
22.  
23.             struct f2a
24.             {
25.                 fixed4 t0 : SV_Target0;
26.                 fixed4 t1 : SV_Target1;
27.                 fixed4 t2 : SV_Target2;
28.                 fixed4 t3 : SV_Target3;
29.             };
30.  
31.             v2f vert(appdata v)
32.             {
33.                 v2f o;
34.                 o.vertex = UnityObjectToClipPos(v.vertex);
35.                 return o;
36.             }
37.  
38.             f2a frag(v2f i)
39.             {
40.                 f2a output;
41.                 output.t0 = fixed4(1, 0, 0, 1);
42.                 output.t1 = fixed4(0, 1, 0, 1);
43.                 output.t2 = fixed4(0, 0, 1, 1);
44.                 output.t3 = fixed4(1, 1, 0, 1);
45.                 return output;
46.             }
47.  
48.             ENDCG
49.         }
50.     }
51. }
52.  

And here's the setup for each cube:


In edit mode, before I actually set the MRTs, the cubes render fine, albeit only to the default render target:



But when I enter play mode, the MRTs get assigned, and the cubes just don't render anything anymore:



Am I missing something very obvious here? I can't seem to make this work at all.

 

Figured it out.

It turns out that everything works, but the Frame Debugger is bugged (lol) and doesn't show the draw calls properly when SetTargetBuffers is used.

Adding a blit to my script does actually render the proper output on screen, in this case yellow cubes, because RT3:

Code (CSharp):

1.     void OnRenderImage(RenderTexture source, RenderTexture destination)
2.     {
3.         Graphics.Blit(colorTextures[3], destination);
4.     }

 

Hey there!
I have been trying to use your script to create render textures to render to, but after applying it to the Camera and setting the number of colortextures to 4 like in your example, I get a list of empty texture slots.
My C# script is identical to yours, except that I added the 4 extra lines from your last post to it.
What could I be missing? Is there a Unity include that I need to add or something?
Thanks!
Ulf

Edit: I am dumb! It only works at runtime. LOL