Controlling Your Fractures in Houdini tutorial help

[ispep]

Following the tutorial; Controlling Your Fractures in Houdini, I've come a bit unstuck with section 9 on creating active and passive points. I seem to be getting an error on my ForEach2 node, with it saying; Warning: Invalid attribute specification: "name"..



...any help appreciated. Trying to get my head around it.

[jrockstad]

This is referring to the Digital Tutors course, correct? As it happens I went through that one as well a couple months back, but our node networks look a bit different from what I can see... for me, that network is in a "head" object corresponding to the head of the statue. You also have a lot of point attributes on your geometry that seem to be related to the Bullet solver which are also not present in my scene. If you've significantly deviated from the course, it might be best to post your scene file so I can get a better idea of what's going on in your version. 

 

One thing I'm noticing is that "name" is a point attribute in your scene while it's a primitive attribute in mine. I'm supposing that this is the cause of your issue, but I'm not sure how you ended up with it - the Voronoi Fracture node should make it a primitive attribute by default. The fix may be as simple as using an Attribute Promote node to turn it into a primitive attribute, so I'd give that a go first, and if it doesn't help, post your scene file and I would be happy to take a look at it. 

[ispep]

Hi, I deviated in the sense that I applied the tutorial to a simple primitive just to make things simple - I also noticed the networks on the tutorial changed from chapter to chapter on one or two occasions (specifically the fracturing, and the delete attribute nodes) and I did try to adapt to that. Where would I place the attribute promote node, I tried placing it after the fracture node but the only name that shows up in the drop down is 'P'. I've attached the .hip file in the hopes you can maybe shed some light; https://www.sendspace.com/file/ez1dup I'd appreciate any help you can provide.

 

Okay, I think the delete attribute nodes were screwing it up. I've bypassed them now. I'm not clear why they were needed actually?

 

But as I follow the nodes down when they get to RBD fractured object tool nodes (the ones created by the shelf tool) the name attribute is changed to a point attribute so I guess that's the culprit. I'm wondering if it's the new option on Houdini to choose between packed/unpacked RBD? The DopImport node seems to be the culprit if I'm understanding the problem.

Edited November 19, 2014 by ispep

[ispep]

here's a new version of the file, I decided to go through it again. I got stuff working that wasn't previously but I'm still having problems. The bits cluster even if I switch clusters off and the fracturing doesn't seem to really take into account my painting. They fall oddly and hang in space sometimes when simulating too, and I can't get group by bounding box in the glue network to select any of the primitives... it sort of works unlike the last file. Maybe someone can make sense of it.

 

https://www.sendspace.com/file/7zbzi8

[jrockstad]

I took a look at your scene - one thing I'm noticing immediately is that you are feeding the dopimport into the foreach2 in your GEOMETRY object, which can result in a host of errors / unexpected behavior. What's happening is that your object is being simulated and then attempting to determine active and passive geometry, which is information that the solver needs before you start the simulation. In my scene I've "split" the network at the point where my final geometry for the simulation is being read in, with one path going off to the foreach2 and the other to the dopimport. Here is a screenshot of my network at that point:

 

 

See if you can get your network set up to something similar and I imagine you should be good to go.

 

Hope this helps - let me know how it goes!

[ispep]

That seems to have made a world of difference, thanks,

 

I also found that relying upon 'automatic' on file nodes was a problem too, it didn't work like I expected. Changing it to read file meant I could use the bounding box group node for example (it wasn't loading prior). The problem I have now is that the glue network doesn't actually seem to be working. When ever I press sim the fractured parts just all fall to the ground. I don't think it's a noob friendly tutorial in truth.

 

https://www.sendspace.com/file/vcqx77

 

An updated hip file if anyone wants to take a peek

Edited November 20, 2014 by ispep

[jrockstad]

In your glue network, I noticed that you're trying to write a .sim file - the File SOP can only read, not write .sim data (you need a File DOP in Dynamics context to write .sims). In this case it is better to simply write out the geometry in .bgeo format. Give that a shot and I imagine you'll be good to go.

 

As for the course not being beginner friendly, I would agree that if you're new to Houdini and are just starting to learn the dynamics system, it is probably a bit overwhelming. There is an introductory dynamics lesson on the SideFX website as part of their First Steps course which you can find here:

 

https://www.sidefx.com/index.php?option=com_content&task=view&id=2207&Itemid=361

 

You may find it worthwhile to get a handle on the basics of dynamics in Houdini, work with some simpler simulations of your own and then return to this course a bit later on.

 

Hope this helps!

 

[ispep]

Cheers I'll check it out. But yeah I think I'll take a step back now, I think I've learnt quite a bit from the tutorial all told but going to struggle to piece it all together I think. Many thanks for the help though.