Question CustomPassUtils.RenderFromCamera not working as expected.

I'm using Unity 2021.1.2f1 and HDRP version 11.0.0

I'm attempting to use a Custom Pass and CustomPassUtils.RenderFromCamera() to render a bunch of objects from a separate top-down orthographic camera to a render texture.

The objects I need to render in this top-down camera are NOT visible to the Main Camera, they're in a layer that's excluded from the Culling Mask of the Main Camera, and only the top down camera should be able to render.

My Custom Pass is pretty simple. I have a second incactive camera I'd like to render from (topDownCamera), a render texture to render to (topDownRenderTexture), and a culling mask containing the objects to render (topDownLayerMask).

Then the Execute function is just

Code (CSharp):

1.     protected override void Execute(CustomPassContext ctx)
2.     {
3.         CoreUtils.SetRenderTarget(ctx.cmd, topDownRenderTexture, ClearFlag.All);
4.         CustomPassUtils.RenderFromCamera(ctx, topDownCamera, topDownLayerMask);    
5.     }

RenderFromCamera() uses the correct position and orthographic projection of my top down camera, but it does not use the correct aspect ratio, which is set to 1 on my top down as I'm rendering to a 512x512 square texture.

Instead it uses the aspect ratio of the Main Camera (or scene camera). That's annoying, but it's not a huge problem as I can compensate for an incorrect aspect ratio.

The big problem is that it won't render anything on the topDownLayerMask if the main camera isn't also rendering it. The objects to render get culled, either by the layer mask or by frustum culling of the main camera.

Now at first I thought it was working fine, but it was actually only working in the editor because I have a Scene window open, and the scene camera was allowing the objects to avoid culling.

With the scene window closed, or with

Code (CSharp):

1.         if (ctx.hdCamera.camera.cameraType == CameraType.SceneView)
2.             return;

included at the start of the Execute function, then nothing renders.

Is there a way I can force the objects in the topDownLayerMask to render duing RenderFromCamera, even though they're not visible in the main camera?

I assumed because RenderFromCamera takes a LayerMask that this would be a non-issue, but it's not working for me.

Is there something obvious I'm missing? Is there a better way to achieve this?

More Info:

Custom Passes is my third attempt at this problem.

Previously I had it working simply using a second camera, but in HDRP this adds >1.5ms of additional render time, even if all the Custom Frame Settings > Rendering flags are set to false, which I assume is meant to streamline the camera.

Then I had it (almost) working by using Command Buffers and drawing the objects with commandBuffer.DrawRenderer(). But in HDRP, commandBuffer.SetViewProjectionMatrices() doesn't work, so I can't render from the viewpoint of my top-down camera.

If either of these previous methods can work with a slight tweak, (either streamlining the use of a second camera, or a working version of commandBuffer.SetViewProjectionMatrices) please let me know, as they'd be preferable to using Custom Passes.

 

Thanks so much, that solved my problem.

All it needed was

Code (CSharp):

1.    protected override void AggregateCullingParameters(ref ScriptableCullingParameters cullingParameters, HDCamera camera)
2.     {
3.         cullingParameters.cullingMask |= (uint)topDownLayerMask.value;
4.     }

Regarding the other approaches I attempted, that work in Legacy, do you expect there's any potential for then in the future in HDRP - that is, streamlining the use of a second camera (stripping all lighting and post processing off it so it can render without a large performance cost), or a working version of commandBuffer.SetViewProjectionMatrices? Or is Custom Passes the only real solution going forward for rendering views that aren't the main camera in HDRP?

 

Hi @antoinel_unity, Looks interesting! Can you share any estimation on that feature (or link to track it). And how it can be used today with HDRP 11 (Custom pass that overrides camera projection)?

 

Looks like CustomPassUtils.RenderFromCamera have a bug with SSS material and Motion blur

SSS material - green "weapon" thats how it looks from regular camera, and black - renders via custom pass.


Same with Motion blur (regardless of SSS material):

 

Thank you.
Will OverrideCameraRendering API help with SSS, motion blur ect. situation?

 

Can you explain more detail on how to change the projection matrix for whole material in Shader Graph? As far as I understand, it is not enough to just change clip pos vertex position, so shadows, lighting and other stuff work properly.