Hi! My name's Bernardo, 3d generalist. I am new here, yesterday I bought a one year license for houdini indie because I would like to use it for fluid sims together with blender. I have fiddled with houdini apprendice before a few times, but I consider myself ahoudini total beginner.

So... my problem is about importing-exporting alembics. I tried importing an alembic from blender to houdini and the file seems empty, although when I try to import the alembic in back in blender all seems fine.

I also created a simple fluid sim in houdini (I'll probably have more questions here later!) and I am now trying to export it in blender with alembic.

EDIT: I managed to export the fluid surface as alembic, but I am still having some trouble with the whitewater particles. To export the alembic it was enough to select the option "render frame range" in the ROP alembic output node

EDIT2: I also managed to export the white water. I was placing the alembic ROP output after the merge node in the white_water import network, but it had to be placed right after the "import_whitewater" node, the first one of the network

So really now I am just having troubles importing an alembic in houdini from blender... maybe I'll also figure that one out and update this post, but if anyone has some help to offer in the meantime, that'd be great!

Hi.

To fix your import issue; try to put an Alembic SOP in Houdini and then point it at the abc file. Also try to use File > Import> Alembic Scene.

I bring in abc's from Blender to Houdini all the time. So maybe the object is there but it is huge or very small. After importing hit Space+G to center the camera on object.

If these do not work try to bring it as an OBJ or an FBX. If they are also not visible, maybe there is a problem with the model? Try importing a simple geometry like a cube or a sphere.

BerkErdag
Hi.

To fix your import issue; try to put an Alembic SOP in Houdini and then point it at the abc file. Also try to use File > Import> Alembic Scene.

I bring in abc's from Blender to Houdini all the time. So maybe the object is there but it is huge or very small. After importing hit Space+G to center the camera on object.

If these do not work try to bring it as an OBJ or an FBX. If they are also not visible, maybe there is a problem with the model? Try importing a simple geometry like a cube or a sphere.

Thank you! I've tried the import>Alembic scene option, but I couldn't see anything. Definitely good to know the space+G shortcut, I'll try that!

So, the "space+G" advice was really good because it's a great shortcut to know, but unfortunately that particular alembic seems to be empty... I'll have to investigate further with that.

In the meantime I have some other question, regarding fluid simulations:

I am quite happy with the fluid sim I've created but I think I am not doing things right when it comes to baking. It feels like I am baking fluid, whitewater and mesh separately and probably overlapping simulation times.

The end result I would like to have is to export everything to alembic so that I can import it in blender. At the moment I have to separately export to alembic each part of the sim. Is there a way I can setup things so that I just bake things once and houdini will calculate all the things and export to alembic (fluid surface and white water) in one go?

Thank you!

Happy that Space+G is useful but sorry to hear that the alembic is nowhere to be found. Again try with a simple object from Blender, like a box or a sphere. Maybe there is an issue with the export.

I am not sure if you can export the mesh and white water together into one alembic. But it shouldn't be that big of a burden since you have to export mesh and whitewater, which means just two alembic files.

If you want the Flip sim to simulate particles then turn it into a mesh, then simulate the white water step by step you can use the Fetch node inside ROPs. You can place as many Fetch ROPs as you need, plug them into each other step by step (for example you shouldn't plug the white water before the flip sim since the white water is based on the flip particles.) You need to select the file cache's of your simulations inside the Fetch ROPs source. Keep in mind that you have to select the render(parm) (when you click the + icon near the filecache it is visible)option of the filecaches not the filecache itself. Select the last node, click on the purple flag, choose Node by node in the Order option. I suggest before simulating for hours/days try a test first with Fetchs.

However, I think baking one simulation then checking if everything is correct then moving onto the other part -especially in Flip- is much better but of course it is my choice.

this is a tip you should know:
everytime you import something in Houdini and it doesnt appear, chances are the scale is 100x so you need to scale it down to 0.01 with a transform SOP node.

also if the geometry has black faces, its probably the "Cd" vertex color attribute and not a Normals issues with the model.

Thank you both for your replies, I'll try to put them to good use!

@BergErdag: I didn't explain things correctly... I didn't want to export white water and surface into a single alemic, just to be able to export them in one single operation, but both of them to their separate file.

Right now I have the feeling that everytime I export to alembic (first water surface and then white water) houdini is re-doing the simulation again. This is probably because I am doing something wrong, but I guess that's normal after a few days of using a new program! You guys are being super helpful, so I'll get there eventually!