Creating Irregular Fracture Patterns

oasfc · Lurker Joined: 20 Mar 2012 Posts: 7

Hi

Im still new to fracturing within Houdini but im trying to recreate a fracture pattern that have similar characteristics to this following image:

http://farm4.static.flickr.com/3264/2851018045_930653b93e.jpg

The problem im facing so far is that the edges to my pattern pattern is very straight, dispite having more than enough points to create an irregular shape when interior details is added. any advise on how to break up the straight fracture patterns would be appricated. I have attached a file for reference. Thanks.

arctor · Posted: Tue Mar 20, 2012 8:44 am GMT Post subject:

you could try a point SOP to add a little randomness ...or the pointJitter SOP

oasfc · Lurker Joined: 20 Mar 2012 Posts: 7

thanks for your response. by adding some jitter after the fracture node i do get the results i want but the points seem to intersect each other as you can see from the attached image. any advice? thanks

arctor · Posted: Tue Mar 20, 2012 11:21 am GMT Post subject:

try just one axis at a time...the pointJitter SOP will move points all over...you may just want them to move on the XZ plane...
or you could use a very slight smoothing...
at this point it's up to you to find some SOP trick to dial in what you want...

HTH

asnowcappedromance · Posted: Tue Mar 20, 2012 11:40 am GMT Post subject:

you could also randomize your point positions in a point SOP by using the random() expression, or you could go into VOPs and have a noise (i.e. turbulent noise VOP or unfied noise VOP) affect only the x and z component of the position vector!

best,

Manu

oasfc · Lurker Joined: 20 Mar 2012 Posts: 7

the main issue is that if make some sort of modification to the points before the voronoi fracture it makes no difference as the node still creates fractures with straight edges, however if i make the modifications after, the points that are meant to "stick" to each other on the surface of the fractured box come apart due to the random nature (as seen in the last image i posted, which didnt have pointjitter applied to on the y axis).

eetu · Houdini Expert Joined: 15 May 2007 Posts: 316

You need to apply noise in world coordinates, not just random. that way the points occupying the same coordinates will be displaced equally.

A Noise VOP in a VOPSOP would be a good way to do it. Or a noise($TX, $TY, $TZ) expression in a Point SOP.

pclaes · Posted: Tue Mar 20, 2012 1:05 pm GMT Post subject:

You probably want to apply a noise based on P rather than on Pt.
You can do this by turning on interior detail on your voronoi fractururd pieces (this is to make sure you have some extra points to deal with).
And then append a vopsop that adds anti-aliased noise to P.

Wire P in th pos of the ani-aliased noise, then add the output of the noise to P and wire it into the output P.
( I would recommend to simplify -> polyreduce your pieces (if you are using bullet) before simming. You can extract their transforms and apply the high res pieces for rendering afterwards.

oasfc · Lurker Joined: 20 Mar 2012 Posts: 7

oasfc · Lurker Joined: 20 Mar 2012 Posts: 7

for reference, it appears to be working but too much, ive tried playing with the aanoise setting but no luck.

circusmonkey · Houdini Guru Joined: 26 Aug 2006 Posts: 1805

simple noise vop

oasfc · Lurker Joined: 20 Mar 2012 Posts: 7

thank you, and everyone else for all your help.