Feedback Does Raytracing support instancing in HDRP 12.1?

Hi Guys

I does raytracing support instancing?

I'm asking as I can't figure out why instanced prefabs do not work with raytraced shadows or raytraced reflections. It also doesn not seem to work AT ALL with pathtracing.

Even if I apply regular HDRP/Lit shaders to the plants and refresh everything, it still does not work.

However, if I directly drag the prefabs into the scene and manually duplicate them, then everything is fine.

This makes me believe there is some kinf of issue with either instances, or Vegetation Studio Pro

 

Hi @chap-unity sorry for the late reply. Here is a reply I received from Lennart from Vegetation Studio Pro:

"Apparently Unity has not made any API to add meshes rendered with the instancing API to the raytracing structure"

Is that statement correct? If not, could you please point me to the correct information?

Apparently that is the reason why I can't get my spawned objects to work with Raytracing. (Objects spawned with Vegetation Studio Pro)

 

Some further info:



Raytracing does not suppor the 1st one in that list. But what about the other 2?

From the sounds of it, DrawMesh uses CPU, but DrawMeshInstanced uses GPU........

 

Thanks @INedelcu
Do you know a rough ETA of when such a feature could become available?

Since its also mostly for foilage, as I understand the wind animation is mostly handled by the shaders, at the same time, could we get something that works with the instancing to also support the shader wind animations?

Currently this is a major hurdle that prevent us from using DXR/Pathtracing for exterior Film sets

 

Yeah since its for film and offline rendering with DXR, we're not overly worried about realtime performance, but of course if it ends up being so bad that frames take longer than traditional DCC rendering, then there's no point of course...

 

This sounds great! I'm looking foward to it. (my main project is a racing game with a lot of instances of the same wheels, cones, fences, guard rails, etc)

 

I really need this function! I'm using DrawMeshInstancedIndirect but I cannot add the instanced meshes to the ray tracing acceleration structure because it requires non-existant Mesh Renderers.

I'm thinking about creating a "hidden" gameobject with a renderer for each instances in a layer not visible to the camera but I really don't like this workaround.

 

Hi @INedelcu
This is the thread I meant to have posted in.
How is work coming along for this?

 

Also figured out that prefabs do not cast raytraced shadows for now.
Please "fix" that soon, thanks!

 

We also desperately need foilage to be able to blow in the wind, while using raytracing/pathtracing, and make LOOOOOADS of duplicates of foilage all over our scenes, using non terrain imported meshes

 

I copied some torusknots in 3dsmax as instances and imported the fbx in Unity.
All knots share the same original mesh, so 3dsmax instances work fine in Unity.
But the knots do not cast raytraced shadows.

I did not instantiate anything at runtime.

 

any updates on this topic? running into a similar problem...

 

Awesome!!!
Looking forward to the nice things this brings

 

I take it that wont make it into the changelog. So how would I know this is in whichever alpha version. Do I look at pulls in github or how does it work? Just trying to sound smart, no idea how to look for a "pull" in github.....

 

@INedelcu could you share working project with 2023.1 on how to instantiate meshes with raytracing, like the example image you posted above? much appreciated

 

Hi @INedelcu thanks for your answer. Any idea when? i cant real find any information or samples online. I really would like to play with this.

Best,
jf

 

Hey @INedelcu!

I just downloaded the newest unity version (2023.1), where i can call the AddInstances as you spoke above in this thread - using the MeshInstanceConfig method. However i cant really get it to work. I would love to to get a sample project showing how this would be set up.

Hope to hear back soon,
Michael V

 

@MichaelHVedeler same here... @INedelcu would be great if you could help us with a sample project.

Best

 

Hi @INedelcu,

wasnt it added here? maybe its not fully implemented, you probably know better than me, just checking.

Best,
j

 

Excuse my ignorance please @INedelcu, but how would I apply this to a simple use case where I have a shrub fbx that I want to instance 10 000 times over a plain, or a tree fbx that I want to instance 50 000 times over same plain?

 

@INedelcu This is amazing, thanks for the efforts and sample projects!

 

thanks a lot @INedelcu this is awsome

 

Hi @INedelcu looking at the HDRP example, is there a way to disable the path tracing, so still have the instances raytraced but in HDRP?

If i disable the path tracing all the instance objects disapear, just the floor remains. Do i need to set any flag on the script?

Cheers,
j

 

Hi @INedelcu do you have any hints for me on this, much apreciated.

Cheers,
j

 

@INedelcu any chance there be a RayTracingAccelerationStructure.AddInstancesIndirect() or a Graphic.RenderMeshInstancedIndirect()? As expected, Graphics.DrawMeshInstancedIndirect does not work with HDRP ray-tracing (SSR/SSGI/Shadows) and since the things I need to draw is defined on the GPU I can't feed an array of matrices to RayTracingAccelerationStructure.AddInstances().

EDIT: I presumed Graphics.RenderMesh() was working with HDRP Ray Tracing, but it does not. The MeshRenderer exposes Ray Tracing settings that are not contained in the RenderParams passed to the method.

 

VFXGraph now supports instanced particles with ray-tracing (within certain limits). How does that work? Do they download the particle count to allocate ray tracing instances?

 

Thanks, this is what I needed to know.

I see that the overload of RayTracingAccelerationStructure.AddInstance() that takes a AABB GraphicsBuffer calls AddInstance_Procedural() internally. Wouldn't it be more clear to expose the method as RayTracingAccelerationStructure.AddInstanceProcedural()?