Gradual Fall of Objects

[Netvudu]

Hey, I have three spare days so I´m taking the chance to properly study some DOP stuff I (clearly) was lacking on....

So, now the topic is, I want to throw in some fractured object into DOPs, but I want it to fall down gradually, not the whole thing in one go...what´s the recommended workflow?

Here is a simple scene with four boxes and I want them to fall one by one, preferably in a method that I can afterwards use for more complex situations (shattered objects for instance). I was trying to use a box as some sort of activator for the dynamics transferring an attribute...something that works nicely for SOPs and POPs, but obviously doesn´t work so nicely for DOPs.

If you check my scene, you´ll see I went literally bonkers trying to make this work. I tried all kind of group things with gravity, with dopfields, dophasfield, dopoption....you name it.

I also tried creating an attribute from SOPs and then calling from DOPs, but that didn´t work either...

At this point I´m willing to accept any ideas on how this is usually done. I´m sure it isn´t tough, only I must be approaching it the wrong way.

GradualFall.hipnc

[sam.h]

Just had a play with this, you can untick "Create Active Object" on the RBD and modify it's data later to activate it.

You can specify a group too. Would this help?

Attached a scene, check out sphere_object1 in the dop net ...

activateRBD.hipnc

[sam.h]

Oops, didn't see your attachment there.

Got it working in your scene!

What I did was made points in your geo -- one point for every object. The point numbers should correspond to the primitive group name and therefore the dops object name. On those points I put an integer attribute, for the activation (just promoted Cd to a detail attribute in max mode to get whether it was active or not.)

In dops, I put a python expression on the group node to get the point attribute and put the corresponding object in the group if the active atrr is == 1. Then used the group in the modify data node to activate the objects.

Seems clean enough to me! Enjoy!

GradualFall.hipnc

[Netvudu]

hi Sam,

it´s quite clear as you said, and it works indeed. I admit I feel a bit...unsatisfied by the solution, because I somehow doubt it´s not possible to do this without resorting to Python (even if it´s a few lines, as in this case).

One thing that frustrates me from DOPs is that, according to the details view I can see all the information from the Geometry, including its attributes, but I cannot reference to those, because if I use a point expression I can only call $OBJ or $OBJID or other similar variables, but not $PT. If i use a dopfield expression, then I apparently can´t call what´s under the field of Geometry...or maybe I´m doing so but it has no effect on the simulation...

It all looks and sounds extremely un-houdiniesque to me. Not being able to access and pass information from some other part of the app without resorting to Python? First time I´ve seen it. In fact I´m sure there´s a way..but I haven´t found it...yet...

But again, thanks. What you suggest does work flawlessly. It´s not something I would like to show to someone new to the software, though...

Edited June 14, 2011 by Netvudu

[sam.h]

You could add a sopnet inside the dopnet, have a dopimport in there and use point() to reference that ... still a bit wierd though!

There should be a way to reference the geo directly .... I don't know how though ... :/

Edited June 14, 2011 by sam.h

[Netvudu]

There should be a way to reference the geo directly .... I don't know how though ... :/

exactly my thoughts!!...

I´m also asking at the mailing list, to check any other ideas. I will probably try also the sopsolver way as it sounds more native, even if obviously slower than the python solution.

[Netvudu]

Hey Sam (and others). At the mailing list I received this scene from Sean Lewkiw which was a great and a reeeally simple way to solve the problem simply by changing the glue impulse and the glue threshold parameters with a Modify Data DOP and reading the color at SOPs.

I think it´s even simpler than your solution and it doesn´t use Python (not that using Python is bad at all, quite the contrary ).

At this thread at SESI´s forum you can find his original scene.

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=21377&highlight=

As Sean´s scene has a lot of secondary options and nodes that weren´t really needed for the basic stuff I recreated a simpler one just in case anybdoy wants to check a simple version on how to unglue pieces from a fractured object. I´m really happy about this setup because it´s a great way to reference SOP nodes from DOPs, and it doesn´t get any simpler than this. It´s entry level stuff and it works wonders.

My scene also has some post-its around to comment the key stuff just in case anybody is relatively new to DOPs.

Hope this helps someone else the way Sean´s scene has helped me.

Unglueing_SOLVED.hipnc

Edited June 16, 2011 by Netvudu

[supertom44]

I just wanted to say a quick thanks for posting your solution it has really helped me out.

I did it slightly different in that I used the colour attribute to change the Active value rather than the glue value.

I was wondering if I could ask your advice on something. I am using your method on a object that I have used the voronoi fracture sop using a scatter node as an input. As I used a scatter node from the source geometry I already have a point at the centre of each piece, however the point numbers do not seem to match up with the OBJID, is there a way to make them or reorder them so they do?

Its not a major issues as using a for each as with your method solves the problem just thought seen as I already have the points would be nice use them rather than having to recreate them.

Cheers.

[Ryan]

I also would like to thank you for posting this scene. It helped me out alot too.

I found a way to ensure that the point numbers match with the DOP objects.

In the expression in the scene file:

point("/obj/Boxes/_TRIGGER",$OBJ,"Cd",0)*10

replace $OBJ with

dopoption($DOPNET,$OBJID,"CopyInfo",copynum)

and in the Group Mask, put something like `dopobjscreatedby("../rbdfractureobject1")`

This CopyInfo data is like an ID number for the objects created by an RBD fracture object, so its more reliable than using $OBJ or $OBJID. Adding new objects into the DOP network by dynamic fracturing can screw up your OBJ order and cause mis-matches with your SOP points.

Edited March 19, 2012 by Ryan

[fxjungle]

First let me thank everyone since this thread is extremely helpful.

Ryan, I am building a set up that uses a fractured object modeled in Maya, exported as an obj and fractured in Houdini.

I think my problem starts in `dopobjscreatedby("../rbdfractureobject1")` part

when I put this into the rbdfractureobject group mask it stops bringing my fractured Geo into the DOP network unless I ad the * before it, but I think this kinda defeats the purpose of what you are doing, and it still wont work.

I am attaching my scene file in case someone can figure out what I am doing wrong.

Thanks

highway_v01.hipnc

[FR3D]

I fixed your file, I would like to thank you big time, as I have been searching for more than a month how to do that effect.

I looked at the example files you posted, as well as your bridge.hip file, compared them, and found out what was wrong without really understanding the scripting part.

-I edited the foreach node

-Cut the color node from the ACTIVATE node to the bridge node(not needed, but i wanted a faster feedback without changing node)

-I changed the attribute condition (higher distance threshold) your file is big so u need to adjust it

-copied the unglue activation from the example file to your file

Well it works, I will be studying more deeply those script and file to fully understand the process.

In the file you will find sticky where I say what I modified.

enjoy as i will!

Also can anyone explain us what the script in the value parameter in the UNGLUE node in DOP means

thank you

PS: now i might be able to destroy stuff the way i want in a simple way

thanks again for the example files, they are of great help

sorry for my awful English

FR3D

highway_v01_fixed.hipnc

Edited June 18, 2012 by FR3D

[FR3D]

Here is another version

using this time RDBfracture object

the result is the same here, but i believe the RBDglue one would be more interactive with other object, still have to test the differences

this one is a lot simpler than the glue version

cheers

Fr3D

highway_RBDfracture.hipnc

Edited June 20, 2012 by FR3D

[huanqing2008]

FR3D,It is very interesting that my file is very similar with yours.What we thought was the same, it is amazing .