What's the general workflow for manipulating large CAD files in Houdini? The viewport is quite smooth, but navigating the multiple layers of nodes that come with an Alembic workflow are challenging - especially with an assembly of 20K - 30K pieces.


For example, say I have a large piece that I'd like to hide from the viewport. I can click it, which instantly brings up the geometry node (fantastic!), and with a click I've hidden in. But, if I navigate away, and later on want to make it visible once again, I don't know a way to easily find the piece's node again.

That's just one example, but you get the idea.

Thoughts?

Thanks,
Luke

I have to say if your using the CAD to do arch viz , Its far better being handled by 3ds max but it depends what your end goal is.

It's more for product vis, now that Vray is somewhat here; CAD files this large are super slow to work with in C4D (my primary app - viewport navigation goes down to 0.3 FPS with these things) but here in Houdini I'm getting a good 15-20 fps with the same mesh.

FBX might work better for this task, as there's still a node hierarchy, but several less levels than alembic creates.

you might look into Node Groups.

I do a lot of large CAD file manipulation.
My workflow is based on naming convention of the parts.
I mostly get .step data from my clients. I convert these data with 3ds max or maya.I rename every piece in groups they belong together(material groups). It is very easy in maya with their rename tool (I hope Houdini 16 will have some strong node renaming tools). Then I Export all pieces in one flat hierarchy as an alembic file.
In Houdini I use the alembic file node inside a geometry node to read the CAD file as one node. The alembic node gives you the possibilities to read primitive groups based on transform node names. Now you can assign your shader to the pieces using their group names.

Maybe you could use the ‘datatree’ panel in ‘object appearance’ mode to hide, delete, filter and even rename nodes at once if used correctly it is a great deal when dealing with a lot of nodes at the same time, I use it a lot when I have to import heavy stuff with lots of pieces from other packages in to Houdini. I hope that helps.

Thanks for the thoughts everyone! Right now I'm working with a technique similar to Nico's, where I'm trying to do as much of the model processing as I can in C4D before export, condensing the assembly into 15-20 primary pieces, each with a slew of polygroups to allow for easy material application in H. It also allows me to blast the primary pieces into their separate sub-pieces right in sops for further animation & sim work.

Ideally, I'd like to do everything A to Z right in H, but the H interface currently isn't designed to work with massive models in that way, as the nodes actually get in the way instead of helping.

Nodes or not I really don't see the difference between managing the geometry let's say in Maya and in Houdini, if I use Alembic and import stuff it builds the same structure as in the ‘outliner’ inside Maya, and If I use the network view as a list I can delete, rename and regroup in a similar way as I would in Maya, I know you are doing stuff in C4D and correct me if I am wrong but as far as I know it is not that different from Maya. You don't need to build groups to assign materials to the Alembic nodes unless you need specifically to manipulate some geometry before, like I said you could use the ‘datatree’ panel to assign, de assign, change materials in several nodes at once and if you need to apply materials to let's say to geometry groups you can also use material stylesheets.
Either way I don't see anything that you do outside that you can't do it in a more streamed lined way inside Houdini but that's just me.

@nicoM - What's your general workflow for fixing / correcting the ghastly normals that CAD files often bring with them? I have a piece of cad geo in C4D that's showing clean normals, and renders very well with Vray & the standard C4D renderer.

But as soon as I export it as an alembic & bring it into H, the normals go haywire, and it renders miserably in Vray here.

I've tried just about every combination of toggles on the Facet SOP, as that appears to be where the problem would be fixed. When I remove the inline points, it cleans up a lot of the faulty normals, but it also removes the points (duh) which creates holes in my geometry that I don't think I can fill.

Ideas?

EDIT: The normal issues seem to be tied to the anistropy in my vray material, so this could very easily be more of an issue as to how this H branch of Vray interprets the normals coming in. Hmmm…



@mzigaib - Agree to disagree? I've become so used to the all-in-one functionality that C4D's object manager presents, that its simply going to take some time to use a very different workflow.

While most of the normal related issues appeared to be fixed by the anistopy, I've found a few more that weren't - so I'm still open to other thoughts as to how this could be remedied.

Thanks!
Luke

@Luke - I would try to apply a normal sop to the parts. For me it helped in most cases.