Testing 3d negative intersection space.

[ian 32]

Testing 3d intersection negative space.

I have to test where, when and why does negative intersection space happen ?

Ian

[ian 32]

ok first test.

this is archicad 15. a very popular arch 2d and 3d program used here in germany.

For testing, I have simply placed 3 walls together and intersected 2.

this is to symbolise the typical 3d model from an archiect, with 3d elements, intersection within one another.

[ian 32]

ok then i have exported it as DXF and opened it in Cinema 4D.

[ian 32]

now as stl into cura...

fingers crossed.....

[ian 32]

ok that was all successful...mmmm good.

[ian 32]

ok test 2

i have offset the height of two of the walls in archicad.

[ian 32]

ok the soffset now in cinema (dxf)

[ian 32]

offset in cura,,,, works

[ian 32]

ok test 3.

simply solid basement elements intersecting one another.

archicad 15

[ian 32]

dxf in cinema4d

[ian 32]

and now as stl through cura.

BANG !!!................ UNDERPANTS !!!! :cry: :cry: :cry: :cry:

[ian 32]

ok testing objest, export from archicad in OBJ format and directly into cura.

[ian 32]

direct export object OBJ into Cura.

Doesnt look good. :-(

[ian 32]

ok test from OBJ to STL in Cinema4D.

Exact same problem with negative intersection space. :-(

[ian 32]

test 4

exporting from archicad 15 in 3Ds file format.

[ian 32]

ok archicad, export to 3DS and then in cinema4d, exported out as stl.

...................UNDERPANTS !!! :cry: :cry: :cry:

same problem as all the above

[alaris2 1]

why not just post the file somewhere and we'll fix it for you. it would save a whole load of pain..

[ian 32]

why not just post the file somewhere and we'll fix it for you. it would save a whole load of pain..

yes but thats not the point !

i use a lot of archicad model files for printing at the moment.

and if i dont understand, how to fix or edit my my models, so i dont get these crazy negative intersection spaces, then im going to simply have to rebuild fresh in cinema every single model.

That is hours, some times days of work !

I have to learn a working process and that is the reason behind this tread.

Ian

ps. thank you for your offer of help !!

[alaris2 1]

perhaps I didn't use enough words in that last post, hence my meaning was unclear -

if you post a file, we can work out what is 'wrong' about it, hence can feed that back to you to change your design flow.

for example, I know of several ways to create inside-out geometry (what you refer to as -ve space) but I can't be sure which one you're currently falling into the trap of (or perhaps you've found yet another)

as a starter for 10, it looks like your model here consists of 5 cuboids and the places where they intersect are causing you problems.

an easy way to create -ve space is to merely group them all in your 3d package. when you export as .stl, the faces inside of others will create the very problem you see here. the order you create the cuboids can occasionally influence which become -ve.

the correct way for most packages is to boolean (union) all of the objects in the scene before export. if you have more than one object in your scene before export, it nearly always causes problems such as -ve space and also if 2 objects sit one on top the other, a slight gap will occur in the stl, leading to weak construction.

actually this last point is interesting in itself. take 2 cuboids and place them one on top the other. export and print. the finished model looks OK at first sight, but often the walls don't quite line up correctly (looks like a model MCUrunner posted recently) and if you hit it against a surface, the model will fracture at the join.

now boolean union and print again. the model becomes a continuous and much stronger model without the strange joints on printing.

you can use this to your advantage when you want to print 'break away' pieces, but that's another topic..

[ian 32]

thank your explainning every thing.

here is my model file.

http://www.thingiverse.com/thing:34421

im really interested to see what you think about it ?

Ian :-)

[alaris2 1]

OK, good news is my previous post is basically correct, so no need to write tons here

your 3ds model consists of an object called 'null' - probably a ground plain or background? I don't this is causing problems, but it's superfluous anyway.

it also has a group, consisting of 5 objects. the individual blocks.

so I loaded it in the *free* hexagon from daz studios. I was trying to find a package you could also use.

if you export as stl, then slice, even in the best slicer in the world you'll find problems as seen below -

notice how k'slicer tries to preserve the perimeters of all the blocks. it's not what you see on the outside that counts, but the internal geometry. it creates -ve space around the perimeters since it can't decide how to represent these areas. it's not quite as bad as SF (Cura) but still wouldn't print how you wanted it, and the model will be structurally weak.

the solution, is to ungroup and then boolean union all the parts together to make a single part. now i can't answer how to do that in your original package, but it isn't difficult from hexagon - select object, hit boolean, select next object, click 'union'. repeat until only one object.

the result of slicing this model is seen below - now that's what you probably intended..

[alaris2 1]

(for reference, it's a slice about half way up the model. green = top surface, blue= interior fill)

[msurunner 2]

AutoCAD simply has the command "UNION"... might be similar in Archicad...

[ian 32]

i wish in cinema 4d there was an auto bolean option.

when i have a model with 2000 parts, it kinda gets crazy doing 2000 bolean options inside one another... computer seems to have a problem as well... ;-)

Ian