HDRP 10: API for rendering an inactive camera to another one

HDRP 10.0's changelog has a section saying there's now the ability to render the contents of an inactive camera via some Custom Pass mechanism: https://docs.unity3d.com/Packages/c....0/manual/whats-new-10-0.html#custom-pass-api

However I can't find much information about this. I found this PR which was merged: https://github.com/Unity-Technologies/Graphics/pull/170 but according to the PR comments and commits, the API is internal and not usable in client code yet.

Is the feature meant to be usable yet? If it's not actually available in 10.0 and the changelog is wrong, is there a plan or timeline for when it will be stabilized and made public?

 

Answering my own question, I've found a public CustomPassUtils.RenderFromCamera function.

 

May I ask if you had any luck using this?
I'm trying to render weapon and arms in a fist person shooter with a fixed FoV but I can't get it to work.

The basic idea was:
* A main camera which renders the whole scene except weapon and arms
* A second camera (disabled) with a lower FoV attached as a child to the first one
* A custom pass which only renders the weapons and arms in the "CharacterFirstPersonFoV" layer

The problem is, I have experimented with this and can't get it to run because there is basically zero documentation for this.

Do I have to call anything other than `CustomPassUtils.RenderFromCamera` in my custom pass?
Can I directly render to the display or do I have to use a render target?

This is what I have for now:

Code (CSharp):

1. using UnityEngine;
2. using UnityEngine.Rendering.HighDefinition;
3. using UnityEngine.Rendering;
4. using UnityEngine.Experimental.Rendering;
5.  
6. class ManipulateFoVPass : CustomPass {
7.     [SerializeField]
8.     private LayerMask layerMask = 1;
9.     [SerializeField]
10.     private CustomPass.RenderQueueType renderQueueFilter = CustomPass.RenderQueueType.AllOpaque;
11.     [SerializeField]
12.     private Camera camera;
13.  
14.     protected override void Setup(ScriptableRenderContext renderContext, CommandBuffer cmd) {
15.  
16.     }
17.  
18.     protected override void AggregateCullingParameters(ref ScriptableCullingParameters cullingParameters, HDCamera hdCamera) {
19.         cullingParameters.cullingMask |= (uint)(int)layerMask;
20.     }
21.  
22.     protected override void Execute(CustomPassContext ctx) {
23.         CustomPassUtils.RenderFromCamera(ctx, this.camera, this.layerMask);
24.     }
25.  
26.     protected override void Cleanup() {
27.  
28.     }
29. }

 

Here ^ the documentation that doesn't even work I guess now we're all set

 

antoinel_unity Hi!
I wanna to do independent fov for first person arms and items, like described in this thread. So I implemented my CustomPass, based on your code. All work well for 3d objects, but the problem is that in my game some items use world space UI. It seems, that camera override doesn't work with UI properly, because in my case UI elements take fov from main camera. I also have been changing first person camera position for test. As a result, 3d objects changed their position in game view according position of first person camera, but UI stayed at same place, like it use position matrix from main camera. Could you look at my code of Custom Pass, please? Maybe I miss something.
I tested it on HDRP 12.1.1 and HDRP 13.1.7.

Code (CSharp):

1.  
2. using System;
3. using UnityEngine.Assertions;
4. using UnityEngine.Rendering;
5. using UnityEngine.Rendering.HighDefinition;
6. using Object = UnityEngine.Object;
7.  
8. namespace DCD.Client.Simulation
9. {
10.     [Serializable]
11.     public class FirstPersonObjectsPass: DrawRenderersCustomPass
12.     {
13.         private FirstPersonCamera _firstPersonCamera;
14.  
15.         /// <inheritdoc />
16.         protected override bool executeInSceneView => false;
17.  
18.         /// <inheritdoc />
19.         protected override void Setup(ScriptableRenderContext renderContext, CommandBuffer cmd)
20.         {
21.             base.Setup(renderContext, cmd);
22.  
23.             _firstPersonCamera = Object.FindObjectOfType<FirstPersonCamera>();
24.             Assert.IsNotNull(_firstPersonCamera);
25.         }
26.  
27.         /// <inheritdoc />
28.         protected override void Execute(CustomPassContext ctx)
29.         {
30.             var currentCam = ctx.hdCamera.camera;
31.  
32.             _firstPersonCamera.transform.SetPositionAndRotation(currentCam.transform.position, currentCam.transform.rotation);
33.             _firstPersonCamera.Camera.CopyFrom(ctx.hdCamera.camera);
34.             _firstPersonCamera.Camera.enabled = false;
35.  
36.             _firstPersonCamera.Camera.fieldOfView = _firstPersonCamera.FOV;
37.             _firstPersonCamera.Camera.cullingMask = _firstPersonCamera.CullingMask;
38.  
39.             CoreUtils.SetRenderTarget(ctx.cmd, ctx.cameraColorBuffer, ctx.cameraDepthBuffer, clearFlags);
40.  
41.             using (new CustomPassUtils.OverrideCameraRendering(ctx, _firstPersonCamera.Camera))
42.             {
43.                 base.Execute(ctx);
44.             }
45.         }
46.     }
47. }
48.  

and here my settings for 3d objects

and for UI

I'm sure, than UI use this pass, because changing near clipping plane on first person camera takes affect on UI.

 

Is there a cheap way (low performance impact) to use custompass to get a disabled (?) camera which only renders UIelements to a rendertexture?

Not sure I understand this custom pass business

Appreciate any help!

 

I'd check out https://github.com/alelievr/HDRP-UI-Camera-Stacking

 

Thx a lot.
i saved another 0.6ms from cpu.

 

@gewl I am using that now, works well - but does not significantly reduce camera CPU overhead.

 

I am using custom pass to render from a disabled camera. This works perfect for opaque and transparent geometry, but it doesn't render UI elements. Any help with this would be appreciated!

Code (CSharp):

1. using UnityEngine;
2. using UnityEngine.Rendering.HighDefinition;
3. using UnityEngine.Rendering;
4. using UnityEngine.Experimental.Rendering;
5. using System.Reflection;
6.  
7. #if UNITY_EDITOR
8.  
9. using UnityEditor.Rendering.HighDefinition;
10.  
11. [CustomPassDrawer(typeof(RenderFromCamera))]
12. class FPSForegroundEditor : CustomPassDrawer
13. {
14.     protected override PassUIFlag commonPassUIFlags => PassUIFlag.Name;
15. }
16.  
17. #endif
18.  
19. class RenderFromCamera : CustomPass
20. {
21.  
22.     public LayerMask foregroundMask;
23.     public Camera UICamera;
24.     public RenderTexture targetRenderTexture;
25.     public Material overrideMaterial;
26.     public ClearFlag clearFlag = ClearFlag.None;
27.     public RenderQueueType renderQue = RenderQueueType.All;
28.     public CompareFunction depthState = CompareFunction.NotEqual;
29.     protected override bool executeInSceneView => false;
30.     FieldInfo cullingResultField, hdCamField;
31.  
32.  
33.     protected override void AggregateCullingParameters(ref ScriptableCullingParameters cullingParameters, HDCamera hdCamera)
34.         => cullingParameters.cullingMask |= (uint)foregroundMask.value;
35.  
36.     protected override void Setup(ScriptableRenderContext renderContext, CommandBuffer cmd)
37.     {
38.         cullingResultField = typeof(CustomPassContext).GetField(nameof(CustomPassContext.cullingResults));
39.     }
40.  
41.     protected override void Execute(CustomPassContext ctx)
42.     {
43.         if (ctx.hdCamera.camera.cameraType == CameraType.SceneView)
44.             return;
45.  
46.         UICamera.enabled = false;
47.  
48.         var depthTestOverride = new RenderStateBlock(RenderStateMask.Depth)
49.         {
50.             depthState = new DepthState(true, depthState),
51.         };
52.  
53.         UICamera.TryGetCullingParameters(out var cullingParams);
54.  
55.         cullingResultField.SetValueDirect(__makeref(ctx), ctx.renderContext.Cull(ref cullingParams));
56.  
57.         CustomPassUtils.RenderFromCamera(ctx, UICamera, /*targetRenderTexture*/ctx.cameraColorBuffer, clearFlag, foregroundMask, renderQue, overrideRenderState: depthTestOverride);
58.     }
59.  
60.     protected override void Cleanup()
61.     {
62.     }
63. }