How to fracture geometry

[michal]

hi everyone, I want to know how to create random polygons on a surface. For example, I have a grid and want to divide it into 100 polygons. I don't want 10 by 10 squares and I also don't want to use "Divide" node to divide it. I want every polygon on the surface is slight different with each other, different shapes, edge numbers, etc. If anyone can post an example file or an OTL, that would be great.

thanks.

[Guest Swann]

Stamp+resample+some noise (expression or Vops) shoud do the trick but it will not give you one clean surface, different Edge numbers complicate this a little.

Propably you think about something like fracturing geometry, from what I see, on this forum, everyone mostly use other applications plugins for this task.

EDIT: If you don't need different edge numbers you can just delete resample and primitive and it will give you similar result to wick3dParticle example

untitled.hipnc

Edited April 27, 2008 by SWANN

[michal]

Propably you think about something like fracturing geometry, from what I see on this forum everyone mostly use other applications plugins for this task.

yeah, fracturing geometry is what I want, but is it very hard to be done in Houdini? oh btw, thanks for your example.

Edited April 27, 2008 by michal

[wick3dParticle]

Hi Michal,

What I did was plugged the grid in to a group, and used a slightly scaled down version of the grid as a bounding box template for the group. I then added 2 attributes for the frequency X and Z to use with a pointSop. In the PointSop's transform I put 2 expressions for the X and Z that use the frequency attributes.

I edited the post because I just realized you wanted unique points, so I added a facet at the bottom and turned on unique points

Hope this helps,

Ilan

gridNoise.hipnc

Edited April 27, 2008 by wick3dParticle

[Guest Swann]

Fracturing grid is not such a big problem, but I don't think that you want to stop only on demolishing grids , and I don't know fast way to fracture object (well, fracture it realisticaly) in Houdini

[Guest Swann]

EDIT: Look on the forums, there was similar topic some time ago, and there somebody was fracturing model of the dragon

Edited April 27, 2008 by SWANN

[Guest Swann]

EDIT: Ups, sorry for this tripple post, Mozilla problems

Edited April 27, 2008 by SWANN

[michal]

Hi wick3dParticle, thanks for your example. I like the way you use the bounding box and the rand expressions in this case. But here comes another question. What if we need to break a complex surface into pieces, not a flat one? I know it's very hard to break solid geometry into pieces (e.g. break a stone into several pieces chunks), but I thought it should be easier for surface (without volume). For example, there is a hollow sphere surface and when it fall down on the ground, it breaks into hundreds of pieces with different shape, and looks very realistic.

Hi Michal,

What I did was plugged the grid in to a group, and used a slightly scaled down version of the grid as a bounding box template for the group. I then added 2 attributes for the frequency X and Z to use with a pointSop. In the PointSop's transform I put 2 expressions for the X and Z that use the frequency attributes.

I edited the post because I just realized you wanted unique points, so I added a facet at the bottom and turned on unique points

Hope this helps,

Ilan

Hi SWANN, the thread you mentioned is this one (http://forums.odforce.net/index.php?showtopic=6257), which is implemented with 3ds Max script.

I also asked questions in that thread, but it seems for now there is no effective way to break solid geometry into pieces of mesh.

Look on the forums, there was similar topic some time ago, and there somebody was fracturing model of the dragon

[eetu]

I haven't tried this, but based on what I've done in other software i would try;

- make a 3d-array of boxes (maybe with 3x3 tripled quads per cube face) right next to each other

- disturb the points with a world-coordinate 3d-noise, so that the points of neighboring cubes stay in the same location

- in a copy sop delete-loop: cookie parts out of the original object with each of the mangled cubes

eetu.

[Guest Swann]

Try this, some more play and it may give good results. Maybe not for fracturing whole geometry, first cut it on pieces and then use this technique on those pieces.

EDIT: Or maybe first this technique and than cut effect of this operation on pieces with another geo.

untitled.hipnc

Edited April 27, 2008 by SWANN

[eetu]

Ok here's a test of what i was rambling about.

Maybe i should try to make it friendly and into a small hda.

Swann: cool technique/idea!

eetu.

ee_frac1.hip

[michal]

hi eedu, it looks really cool. Is there any possibility to make those seams invisible before it is fractured? SWANN, thank you too. I never know that I could use isosurface this way:)

[stevenong]

There is a Fracture Digital Asset on the SESI exchange which doesn't seem to do much on the surface but it is pretty useful when you dive in & expose more controls. I think in the RBD Fracture Help docs, there is an example of a breaking rock and the rock is fractured with the Fracture Digital Asset.

Cheers!

steven

PS I edited the topic's title to make it more relevant to the question.

[Guest Swann]

Ok here's a test of what i was rambling about.

Maybe i should try to make it friendly and into a small hda.

Swann: cool technique/idea!

eetu.

Yeah, thats what I was taking about, first fracture with isoSurface than cut effect with another geo (your technique eetu), and it gives amazing good results, Even without merging those techniques they can give nice results, both for different state of breaking.

Edited April 28, 2008 by SWANN