Question How do I get ObjectIDs in HDRP?

fct509 · May 13, 2021

Does anyone know how to get pull things like the Object ID, Primitive ID, or Instance ID by using a Custom Pass System in HDRP 7.5. I came across a post 8 months ago from someone that claimed they did it, but they didn't actually say how (and I can't seem to find the post anymore).

I think it's possible on a technical level, but I'm a bit lost on what to do. The official documentation for HDRP isn't really much help in this.

chap-unity · May 14, 2021

Hey, let me give you some pointers on how to achieve that.
You will need 3 things;

First, you need a script that assign a color to each renderer in your scene. Here's an example that assign a random color each one and put that color in a new property called "ObjectColor". However, you can pick a color based on the material instance ID or the shader ID for example :

Code (CSharp):

var RendererList = Resources.FindObjectsOfTypeAll(typeof(Renderer));

System.Random rand = new System.Random(3);

foreach (Renderer renderer in RendererList)

{

MaterialPropertyBlock propertyBlock = new MaterialPropertyBlock();

float hue = (float)rand.NextDouble();

propertyBlock.SetColor("ObjectColor", Color.HSVToRGB(hue, 0.7f, 1.0f));

renderer.SetPropertyBlock(propertyBlock);

}

Then you will need a new shader graph that will retrieve that color and assign it to the base color of the object. You can create a very simple unlit and link that to the base color. Then create a material from this by right clicking on the graph and select "Create > Material"

Lastly, you need to setup your custom pass volume and output the target color buffer to the camera to be able to see something happening.

If you do not want to display that on the screen but export them as image to be used later you can set it to custom and use a script to write them to disk for example using this API.

Hope that helps.

fct509 · May 15, 2021

chap-unity said: ↑

Hey, let me give you some pointers on how to achieve that.
You will need 3 things;

First, you need a script that assign a color to each renderer in your scene. Here's an example that assign a random color each one and put that color in a new property called "ObjectColor". However, you can pick a color based on the material instance ID or the shader ID for example :

Code (CSharp):

var RendererList = Resources.FindObjectsOfTypeAll(typeof(Renderer));

System.Random rand = new System.Random(3);

foreach (Renderer renderer in RendererList)

{

MaterialPropertyBlock propertyBlock = new MaterialPropertyBlock();

float hue = (float)rand.NextDouble();

propertyBlock.SetColor("ObjectColor", Color.HSVToRGB(hue, 0.7f, 1.0f));

renderer.SetPropertyBlock(propertyBlock);

}

Then you will need a new shader graph that will retrieve that color and assign it to the base color of the object. You can create a very simple unlit and link that to the base color. Then create a material from this by right clicking on the graph and select "Create > Material"

View attachment 853844

Lastly, you need to setup your custom pass volume and output the target color buffer to the camera to be able to see something happening.

View attachment 853868

If you do not want to display that on the screen but export them as image to be used later you can set it to custom and use a script to write them to disk for example using this API.

Hope that helps.
Click to expand...

Thanks, I'm going to have to give this a try over weekend to see if I can get it to work.

But, as for the API, that's not actually useful for Unity 2019.4 LTS because Unity 2019.4 doesn't have that API. The AOV API is present for Unity 2020.3 LTS, even if the documentation sucks. Yet, the project I'm working on, is built on Unity 2019.4 and HDRP 7.X. Newer features that are in HDRP 10.X aren't applicable, this is why I mentioned the general versions of Unity and HDRP that I'm using.

But, as for the idea of trying to use the Renderer to set the color, thank you. I am going to have to try that.

fct509 · May 31, 2021

So, I took a closer look, and it turns out that the AOV API wasn't added to Unity with 2020.2. It's even part or HDRP 7.4 and Unity 2019.4. It was only added to the manual with Unity 2020.2 and some ability to work with Custom Passes was added to the API.

To, @chap-unity, sorry for saying that the AOV API was not applicable. And, sorry for the much, much meaner things I was thinking.

newguy123 · Oct 18, 2021

So could anybody actually get this to work? And does anybody have an actual step by step on how to achive this? Not just snippets of code and not saying how it all ties together?

For example, I'm on 2021.2.0b16 with HDRP 12 and Raytracing. I need to get a pass like this out with Recorder, or any other way that is native to Unity

It's such a common pass in compositing and VFX, Architectural work, that I'm surprised something like that does just simply ship already made. Why do we have to keep re-inventing the wheel with Unity?!?

Apologies for my tone. Deadline approaching and frustration setting in. Any time saved moving from traditional DCC rendering, to realtime, has been lost due to not being able to do the simplest thing by default, but by having to work around various workarounds, re-inventing the wheel. etc.

If there's a good samaratin out there that could lend a hand on exactly how to get a pass like the one above, or at least show me how to do a mask for a single group of object instances, or a mask for a single material instance, I would greatly appreciate it!!!
(taking into account we can put basic code together, but we're artists, not a coders)

Matjio · Oct 19, 2021

Hi!
We have added ObjectID to HDRP recently: https://docs.unity3d.com/Packages/c...stom-Pass-Creating.html#object-id-custom-pass
Unfortunately, it is not yet integrated in the Recorder.
Best,
Mathieu

vladala · Oct 19, 2021

Hello,

Unfortunately I cannot do better than the previous posts suggesting code snippets.
Supporting a new AOV pass in the recorder is not straight forward enough to fit on a forum post.
I have added it to our recorder backlog and will do my best to prioritize it.

Sorry that I was not able to be more helpful.

HIBIKI_entertainment · Oct 19, 2021

vladala said: ↑

Hello,

Unfortunately I cannot do better than the previous posts suggesting code snippets.
Supporting a new AOV pass in the recorder is not straight forward enough to fit on a forum post.
I have added it to our recorder backlog and will do my best to prioritize it.

Sorry that I was not able to be more helpful.
Click to expand...

Good to know this at least, and good luck moving forward

newguy123 · Oct 19, 2021

Matjio said: ↑

Hi!
We have added ObjectID to HDRP recently: https://docs.unity3d.com/Packages/c...stom-Pass-Creating.html#object-id-custom-pass
Unfortunately, it is not yet integrated in the Recorder.
Best,
Mathieu
Click to expand...

@Matjio will that be backported to HDRP 12 in 2021.2?

newguy123 · Oct 19, 2021

I managed to get a Custom Pass ObjectID out! Super Cool!

However, I have raytracing enabled and so using deferred. There's an error about Forward only.

Matjio · Oct 20, 2021

Great!
Note that it is not an error, just a warning that some objects might not render.
Check the doc here: https://docs.unity3d.com/Packages/c...Custom-Pass-Creating.html#forwardonly-support
Raytracing should work with Forward or Deferred.

newguy123 · Oct 20, 2021

Any Idea why objects spawned with Vegetation Studio Pro are not affected by Custom Pass?
I checked layers of the VSPro object, I checked the original layers of the tree prefabs used in spawned, but not seeing why it would not be afffected...

chap-unity · Oct 20, 2021

Shot in the dark: could that be because they are spawned inside a layer that is unnamed by any chance?

newguy123 · Oct 20, 2021

chap-unity said: ↑

Shot in the dark: could that be because they are spawned inside a layer that is unnamed by any chance?
Click to expand...

no idea, how can I check that?
also in my custom pass, I said to use "Everything", so theoretically that should use all layers, including unnamed ones isnt it?

newguy123 · Oct 20, 2021

chap-unity said: ↑

Shot in the dark: could that be because they are spawned inside a layer that is unnamed by any chance?
Click to expand...

No I dont think that's it. In its settings it says everything is on default layer:

PutridEx · Oct 20, 2021

Maybe because they're instanced or indirect instanced?

newguy123 · Oct 20, 2021

PutridEx said: ↑

Maybe because they're instanced or indirect instanced?
Click to expand...

Bingo!
If I set them to normal, then it works as expected. Why is that I wonder....

PutridEx · Oct 20, 2021

because life is hell
Instanced and indirect instancing also doesn't get motion vectors, so TAA turns into a ghost town...
And you basically NEED instancing for vegetation.

newguy123 · Oct 21, 2021

PutridEx said: ↑

because life is hell
Instanced and indirect instancing also doesn't get motion vectors, so TAA turns into a ghost town...
And you basically NEED instancing for vegetation.
Click to expand...

LOL

I've actually been very happy with how DLSS is working for me. No more TAA for me!

PutridEx · Oct 21, 2021

newguy123 said: ↑

LOL

I've actually been very happy with how DLSS is working for me. No more TAA for me!
Click to expand...

Ideally everyone would have RTX and use DLSS , but if your making a game and it's intended for the masses, TAA would be the best choice available

newguy123 · Oct 21, 2021

Just circling back to this.

Isnt that then an issue with the Custom Pass? ie it Doesnt detect or render Instanced or Instanced Indirect objects?
Surely it should be able to deliver a custom pass to anything and everything?

Then tying this back in with my situation, setting VSPro to normal mode, somehow makes the custom pass work. However VSPro normal mode uses Graphics.DrawMesh.
Raytracing limitations says that Graphics.DrawMesh is NOT supported. But then, how on earth does it work fine in my case, especially with custom pass, and the other methods does not?!?

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