I brought a tool into Maya 2018.7 and the output is always at the origin. From what I can understand reading the forum posts, the geometry I selected is parented under a locator that is at the origin so the tool reads the parent's transform and that's where the Output will be?

Is there a way to have the Tool read the geometry/shape's transform instead?

Thank you.

Cheers!
steven

The Maya plugin currently has no concept of a transform. All of its inputs are interpreted in world-space. For example, if you move a poly sphere somewhere off the origin and provide it to your HDA, it will come into Houdini as if you had just moved the vertices - not the transform.

Would you mind attaching your HDA here, or send it to support so that I can take a look?

Hi John,

I modified the "Labs Snow Buildup" tool slightly for this but the Labs tool itself should demonstrate to you what I'm seeing.

So the geometry is nested like so:

Guess I have to duplicate the geometry and bake the transforms for the tool to work.

Thank you.

Cheers!
steven

Hello, I think my question is related.
Using Houdini Engine, I imported into Maya a Houdini Asset that's just a simple spherical particle cloud.
The particles appear in the scene at the world center and render well (Arnold).
But if I move the asset from the center, it will still render as if it's still in the center!
I tried moving the top node (named after the asset) and the particles themselves (usually named file1_0), but I get the same result.
So how can I move an imported particle cloud far from the center and render it correctly?
Thanks
GZ

I was able to select the created nParticles system and move it without issues. Would you be able to attach your hda here?

Hello John, thanks for the help.
It's not a simple problem with moving nParticles around. It's the rendering that does not work.
Please watch the enclosed picture, it says it all.

The Houdini asset reads a *.bgeo.sc cache file sequence.
In the Maya scene, the nParticles (imported Houdini asset), need to be translated away from the scene center.
It might be an Arnold rendering issue. But I can’t compare with the Maya Software Renderer, as the nParticles always appear black in the render view, even if I put a material on them.

Do you have the same behavior in your Arnold render in Maya ? If not I could send several files.

I just tried with a normal particle system with Arnold, and the particles moved properly with the container. Could you please send your hda and bgeo files to support so that I can take a look?

Hi John,

Please find the file on this link :
https://1drv.ms/f/s!Aqrh36ch9Q9Hn6wJ4Jyk7SL3yPZQkQ
The file is called “forsidefx.zip”.
I put the hiplc file, the hda asset, the geo cache files, and the Maya scene.

If you create normal Nparticles in Maya, you can move the emitter, and they render perfectly. But an imported HDA refering to *.bgeo.sc files does not work so well. I think you alluded to this in a post above when you said "The Maya plugin currently has no concept of a transform." Also I'm currently talking to Houdini tech support and they said the same thing.

In Maya, transforming this "file1_0" nparticles is not changing the particles' position attributes. When I move "file1_0", it does change the value in the channel box > translate X Y Z .
But the per-particle position data for the nparticles must change for the renderer to act correctly.

in Houdini, if you were to append a transform sop to the file sop in the hda provided, then in the Geometry Spreadsheet, I can see the P(position) data for each point move as I change the translate parameters in the transform sop.

In conclusion: Moving the asset in Maya is not enough because I’m not really moving the particles. Moving the particles has to happen inside the asset.

I attach a picture that shows what I did to solve the problem. I did this AFTER I created the files I have on the link above.

But I find this system complicated. I would like a straighter approach, such as :
is it possible to create in Houdini some object that would move the particles, and have this object imported into Maya? I tried to create a null in Houdini, link the "P_Transform" (from the attached pic) channels to this null‘s channels, and package it inside the asset along with the particles. However, when I import this inside Maya, I can’t move the Houdini-made null…
So I'm still looking for a more handy solution.

Taking a look at your Maya scene, I see that you have keyframes set on the nParticle node. If I render the scene at frame 50, I see the particles in the center, and when I change to frame 60, I see the particles at the edge of the frame. In both of your screenshots from yesterday, you were rendering at frame 50. If you hadn't commuted the changed transformation to a keyframe and then rendered, since you have motion blur enabled, it would change the current time to a subframe, which would cause the particles to snap back to their original location.

If I delete the keyframes, I can move the object wherever I want and it seems to render correctly.

Hey John, I'm not sure how you did it. In the Maya scene I deleted all keyframes, I disabled motion blur in Arnold render settings and I moved the particle object... same problem!! What's your magic trick?

I was running Maya 2022. I just tried running your scene in 2018 and the particles don't move. Perhaps this was an arnold bug that was fixed? If you can't update your version of Maya, perhaps you could try installing a newer version of Arnold?

Hello John, thanks again for the help!
So, I tried the scene on Maya 2022, no keyframe, no Arnold motion blur. I also upgraded Houdini + Engine to version 18.5.578 . And.... SAME PROBLEM. So now I'm lost. Is there something you do on the scene that I'm not aware of? Are you using the "bake asset" button (I'm not)?
Thanks
G

One more thing : the problem does not happen with an imported VDB which appears as a Fluid in Maya : I can move it and the Arnold render will reflect that, in Maya 2020.

Ok I finally found a solution that works!!

First some information:
¤ The problem is not related to Maya 2020 and its Arnold version. The same behavior occurs in Maya 2020 and Maya 2022.
¤ In Houdini, While creating an asset, it is NOT necessary to add a Transform node, as I did in the picture "Move particles in Maya" above.
¤ In Maya, after importing the asset, it is NOT necessary to create a rig-like object and to add expressions to the asset’s channels, as I did in the picture "Move particles in Maya" above.
¤ motion blur and keyframes are NOT involved.

I've done a lot of testing and finally got a Houdini Particle asset that worked: when I was moving it away form the scene center, Arnold rendered it properly, even with motion blur and keyframes. But in my asset, the particles were not alone, there were also 2 VDB volumes, appearing as fluids in Maya. When I imported another asset in another Maya scene, the same problem came back, because this asset was containing ONLY particles and no Houdini volume / Maya fluid. So the solution is a bit weird, but here is what I should do, whenever I need to import Houdini particles into Maya via Engine:

In Houdini, I need to include in the asset some VDB Volume, even a light one. It's just a dummy. I beleive it needs to be a volume. I tried to include a second particle system and a cube, but they didn't work for me.
In Maya, import the asset using Engine. It's possible to hide the "Fluid" object. Translate the Asset object away from the center and Arnold-render it: it works!
Enclosed is a pic that summarizes this.

Now what's strange it that the asset I put in my Onedrive only had particles. But still John had no problem with it. So there's still something I miss here…
So I would apreciate if some other people test this : import Particles only , move them away from the scene center, and render them using Arnold… Tell me if this works, thanks!

Hey, I found a second solution to this problem.
Go to menu windows > settings preferences > preferences > settings > animation > Evaluation > evaluation mode = DG.
Then there is no need to add a volume - fluid.
But we may need to revert to parrallel for other Maya operations.