hello houdini vets!

i have a (hopefully) quick question to ask that i can not seem to solve myself. i am currently creating a test case for a school assignment using the destruction tools within houdini.

What i want to do i import an object into houdini, fracture it, smash a ball into it (like one of the very first tutorials) and then export it back into maya.

I have currently managed to do all of this however there is one issue. the fractured chunks get imported into maya as one object, i can seperate these however every chunk is then seperated into inside and outside objects.

Is there a way to get them to export as whole chunks? not as seperate objects for the inside and outside pieces?

Many thanks from a new houdini enthousiast

This is just a guess but I think your problem can be fixed by removing the inside and outside groups that voronoi fracture creates. Then you should only get groups for each piece.

hi erik

no unfortunately turning “create output groups” off or erasing the names of interior and exterior group does nothing..upon import to maya and seperation the inside and outside pieces are still seperated..

is there maybe a possibility to merge or fuse these two groups?

That's not what i meant.

I mean like this. This creates separate pieces that got both inside and outside corrected correctly when i export as obj.

ooh result!

when i import your cube into maya it does exactly what im looking for!
however when i tried to replicate it on my own wall it didnt do it? all i did was add a group node then in the edit/delete/ tab put inside and outside in the group bar.

was there anything else you did?

p.s my fracture is also using different nodes…your uses a isoofset1 and a scatter1 before going into the fracture. mine uses converttofog1 and chunkcenters is there any reason for this and should i be concerned about it?

It is the same type of nodes just named differently.

You need to un-tick Enable on the Number tab of the Group Geometry node. If not it will create one group that contains all geometry and that will mess up the export.

Alternatively, on the Groups tab on the VoronoiFracture node, just clear out the values for the names of the Interior and Exterior groups, and those groups won't be created in the first place.

@ erik

still not working even with it unchecked. However, when i try to import mine into maya i do get a notice saying:

Your OBJ file contains faces shared by multiple groups.
maya cannot create multiple objects for this file.
a single mesh object will be created instead.
the OBJ group information will be captured in maya sets.

I do not get this message when importing the cube from your file.

@ johner

That doesnt work, first thing i tried

He meant to remove inside,outside but keep piece. Do you have any other groups on your geometry? It worked here but i could not use your wall file because you didn't include it so i used a simple box instead.

ive swapped out my imported .obj for a houdini box and it works….weird that it doesnt like it for imported objects. any idea why this is? for this test case it doesnt really matter as its just a stretched out cube which i could do in houdini too. However if i want to shatter more complex geometry that i need to import from maya its not going to work…

It is probably because that the imported geometry contains groups and therefore by only deleting inside and outside you still have polygons that belong to multiple groups.

nope…literally just a cube made in maya and scaled. exported as obj and imported in the geometry node in houdini…weird stuff..

Maya automatically creates groups when you export. When I exported a cube and brought it into Houdini it contained two groups: default and pCube1. I guess you have a similar situation.

hmmm thats weird….any idea for a fix?

You can export without groups from Maya or delete them inside Houdini. You can use * in the Group Geometry node to delete all groups and put that after the File node before you fracture the object.

woohoo! works! u guys rockkkk!

ok one more question to finish this thread off and then it can be locked.

at the moment all the pieces are being imported as individual objects. (i have 10 objects in my outliner)

what i would like is for them to be imported as 1 object as am importing a whole series of .obj to be combined in to a blendshape. once i make the blendshape i then want to seperate it to get my individual and animated chunks.