Question Overwriting the camera projection and worldToCamera matrix in a custom pass

i have successfully overwritten both - the camera projection and worldToCamera matrix - in URP using a
ScriptableRendererFeature to render with an orthographic camera top down without having to use a second camera.
just using cmd.SetViewProjectionMatrices(MyworldToCameraMatrix, MyprojectionMatrix); did the trick.
then using:
context.ExecuteCommandBuffer(cmd);
context.DrawRenderers(renderingData.cullResults, ref drawSettings, ref filteringSettings);
was all i needed to get the things rendered into my render texture a virtually no costs.

so i wonder if this is possible in HDRP somehow as well.
my first test using a CustomPass and more or less the same setup and finally:
HDUtils.DrawRendererList(renderContext, cmd, RendererList.Create(result));
unfortunally failed.

it would be great to render out a top down projected rt for anything like displacement just using the default camera and its culling results.

 

I apologize for necroing this thread but I've run into this same problem just today. Is there any chance you've gotten this working?

I first tried using

SetProjectionMatrix()

without luck. After checking the custom passes repository I found that CameraDepthBake.cs uses

SetProjectionMatrix()

so I tried it but found that it did not work either, it only mirrored the final result down the middle with the objects still being drawn in a non-orthographic manner. Lastly, I tried additionally setting the view projection matrix along with a few others (included in the code below).

The code:

Code (CSharp):

1. protected override void Execute(CustomPassContext ctx)
2. {
3.     // cache the camera's previous matrices
4.     var prevProjectionMatrix = ctx.hdCamera.camera.projectionMatrix;
5.     var viewMatrix = ctx.hdCamera.camera.worldToCameraMatrix;
6.     var prevViewProjectionMatrix = prevPMatrix * viewMatrix;
7.  
8.     var orthographicProjectionMatrix = GL.GetGPUProjectionMatrix( Matrix4x4.Ortho(0.0f, 1.0f, 0.0f, 1.0f, -1.0f, 100.0f), true);
9.  
10.     var viewProjectionMatrix = orthographicProjectionMatrix * viewMatrix;
11.  
12.     ctx.cmd.SetGlobalMatrix("_ProjMatrix", orthographicProjectionMatrix );
13.     ctx.cmd.SetGlobalMatrix("_ViewProjMatrix", viewProjectionMatrix );
14.     ctx.cmd.SetGlobalMatrix("_InvProjMatrix", orthographicProjectionMatrix.inverse );
15.     ctx.cmd.SetGlobalMatrix("_InvViewProjMatrix", viewProjectionMatrix.inverse );    
16.     ctx.cmd.SetGlobalMatrix("_CameraViewProjMatrix", viewProjectionMatrix );
17.  
18.  
19.  
20.     ctx.cmd.DrawMeshInstanced(
21.         myMesh,
22.         0,
23.         myMaterial,
24.         0,
25.         myMatrices,
26.         myMatrices.Length-1
27.     );
28.  
29.     // reset the matrices
30.     ctx.cmd.SetGlobalMatrix("_ViewProjMatrix", prevProjectionMatrix );
31.     ctx.cmd.SetGlobalMatrix("_InvProjMatrix", prevProjectionMatrix .inverse);
32.     ctx.cmd.SetGlobalMatrix("_InvViewProjMatrix", prevViewProjectionMatrix .inverse);
33.     ctx.cmd.SetGlobalMatrix("_CameraViewProjMatrix", prevViewProjectionMatrix );
34. }
35.  

Any help at all would be immensely appreciated! I've lost a few hours to this problem already and hopefully this will help others from falling down this same hole

Edit: I've also tested the code with

HDUtils.DrawRendererList()

with similar results so I don't believe that

DrawMeshInstanced()

is the culprit

 

i set a custom global worldtoview matrix and custom shaders. this works fine in hdrp 7 and 9. i haven't checked it in hdrp 10 tho.

 

Ah, I'm sorry, I forgot to include the version - I'm using the 9.0.0-preview.33 package version. Also, I'm on 2020.1.10f1 if that helps at all either.

So after checking the docs it looks like

CustomPassUtils.DrawFromCamera()

isn't available in version 9.0. I'll take a peak in the hdrp package repo page for the CustomPassUtils to see if I can just reproduce the functionality in 9.0.

Also, does the SetGlobal API also not work in 9.0?

 

Thanks you! By custom do you mean a matrix which is a property of a those shaders?

I've looked into trying to replace the transformation by the projection matrix using a custom shader but I'm not sure exactly where it happens in the hdrp shaders, or rather I haven't yet tracked down which file and line it happens on. As of now I've just made a copy of the unlit shader with some of the bells and whistles removed and its working. If you could point me to where to find the transformation I'd be extremely grateful!

Edit: Looks like I found it,

VertMesh()

in VertMesh.hlsl

 

Sorry hyjacking this thread a bit. I'm having trouble wrapping my head around render passes a bit. This is the exact thing I want to do right now, well almost anyway, do you mind sharing the code for this?

 

nowadays CustomPassUtils.DrawFromCamera() should make your life easier already.