What is this? weird things on model after using voronoi fracture

[anicg]

Hi,

I have imported a model, applied voronoi fracture and some weird blue faces started showing up, I have made a short video showing the problem:

https://www.youtube.com/edit?o=U&ar=1&video_id=bWiPswILZ0s

any idea what these are? is it an issue at the modeling stage? normals?... 

[fencer]

Not the best idea to fracture geometry like this, full in one take, separate everything to blocks/groups (basement, roof, walls...) and do it individually.

 

[anicg]

Thank you, I have do it by sub-element and it is still there actually I can see it clearer, I made another video:

Any idea what there are?

Edited October 26, 2018 by anicg

[Yon]

yea its because your model is garbo, you could try your luck with a fuse and clean sop but prob have to fix it yourself or send it back to modeling dept if you have one..
or just use booleans as its the more modern way 
and the piece of house your fracturing at the start there - way to big, each door frame and wall should be fractured on its own (use a for loop), and it looks like the walls are planes - you never want planes always some depth
 

Edited October 26, 2018 by Yon

[anicg]

is this a problem with normals?

[Yon]

only one way to find out

[fencer]

Share one element to check. Something wrong with your geo.

Edited October 26, 2018 by fencer

[anicg]

Here is the fbx:

https://wetransfer.com/downloads/253a5978e9bc8ff18d6b0f725f9349d020181026214450/ad09a91e71ea30a312abc3cf0aa17cad20181026214450/5fe3e3

thanks

[fencer]

So, your geometry is not closed. 
Check basics about rbd preparation, https://www.sidefx.com/learn/getting_started/

rbd_ready_geo.hipnc

Edited October 26, 2018 by fencer

[Noobini]

because by default, the voronoi fracture has Create Interior Surfaces ON. If you untick, you won't get the problem.

Use a simple box to visualise the problem, if you voronoi fracture this box.....the box is paper thin, but after the fracture it magically has the 'inside' (use explode to see)

Now the box is simple, so there's no problem there...but your geo is very complexed......all paper thin...but the fracture is trying to create internal geos and eventually, things break down.

Edited October 26, 2018 by Noobini

[anicg]

17 hours ago, fencer said:

So, your geometry is not closed. 
Check basics about rbd preparation, https://www.sidefx.com/learn/getting_started/

rbd_ready_geo.hipnc

Paul, grateful if you could point me to the exact video you have in my about rbd preparation.

[anicg]

17 hours ago, Noobini said:

because by default, the voronoi fracture has Create Interior Surfaces ON. If you untick, you won't get the problem.

Use a simple box to visualise the problem, if you voronoi fracture this box.....the box is paper thin, but after the fracture it magically has the 'inside' (use explode to see)

Now the box is simple, so there's no problem there...but your geo is very complexed......all paper thin...but the fracture is trying to create internal geos and eventually, things break down.

Many thanks, does it mean that when modeling I should avoid "paper thin" and make sure everything has some dept? do you have some checklist to make sure the model is ready for destruction? I will use existing models, or make them, but in both cases I need to end up with something I can use.

And for this current building model, do I just need to add dept to the paper thin parts, or is there more to worry about? because the chimney is not paper thin, yet it has the same problem.

Edited October 27, 2018 by anicg

[vicvvsh]

The chimney is not closed too. Take a look to hip

chimney_preparetion.hipnc

[Noobini]

I think you have to consider both ideas.

01) is the object SOLID

02) is it properly closed.

So if you were breaking a large rock, let's pretend somewhat spherical shape, so break a 'noisy' sphere normally...looks perfect because it's a closed shape AND we know a rock is solid inside (ignore porous rock)

But if you live in a house made of a repurposed shipping container...ie. a box, sure it's a closed shape, fine but when you break it...it's solid inside....surely you CANNOT live in a house that is SOLID inside. So then you have to give the walls 'thickness' like in real life, so when using extrude...remember to output back side...(and check for any other holes too)

Edited October 27, 2018 by Noobini

[remsug]

I think.. turn off Display Option

Display Options - Markers - Tint Backfaces(primitives tap)