dops POPS Geo wrapping from DOPS?

[mstarktv]

I'm new to Houdini but I know that when version 13 came out, POPS AND DOPS were merged into Dynamics. For the life of me, I can't figure out how to make particles into geo shapes. I'm not trying to create POP Particles that are then converted into proper rigid bodies. I'm literally just trying to take the POP Particles and add a shape to them. So yes, there will be intersections between the particle shape and collision geo.

I attached my file. I could get the particle to be wrapped/meshed as spheres if I did use a copy sop on both a sphere and a POP setup. But trying to have those particles collide with other geo wasn't working. 

If I'm being confusing - in the most basic form, I just want the colliding particles to be meshed as a sphere. Those spheres don't need to be collision accurate, they just need to wrap the particles.

Thank you so much for any help!

Best,

Michael

POP_SHAPES.hipnc

[mestela]

This should do what you're after.

 

-matt

 

POP_SHAPES_2.hipnc

[mstarktv]

Thank you so much, Matt! This has been one of my roadblocks. I kept running into the problem that you noted in the sticky - which is that I was exporting everything as 1 object. I could;t figure out how to filter out just the particles to apply geo shapes to them. I can rest easy now. 

By the way, I reference your site pretty much every day because I keep forgetting VEX naming conventions  

[mestela]

Heh, cool. Tell your friends!

 

[Farmfield]

I already know and I'm not sure Michael has other friends.

 

As for the subject, I messed about some with the instance node, though not sure why you would use that instead of packed primitives? Guessing that is a remnant from before they implemented packed primitives..?

[mstarktv]

You're never alone when you have books! Johnny, can you post your file? My whole reason for wanting to basically have "dumb particles" is for anything you would useful particle collisions that aren't of "hero importance." So, sparks, smaller debris, whatever else.; things where collision precision doesn't matter.

Edited April 25, 2016 by mstarktv

[Farmfield]

My file? For the setup playing with instances I didn't save that one, but check the help file, just search for instance - or add an POP Instance in DOPs and access it's help to go to the section directly.

[mestela]

You might dig this other thread (skip down to Tomas's excellent post), and/or the gif happy wiki version I posted:

http://www.tokeru.com/cgwiki/index.php?title=HoudiniDops#Emit_packed_prims_into_RBD_sim

http://forums.odforce.net/topic/25792-emit-packed-rigid-bodies-efficiently/

 

[mstarktv]

WELL THANKS FOR NOTHING JOHNNY! But no, that's what I did. I'm glued to the help file.

Also, Matt, I don't know how you did it, but you read my mind. This was actually something I was trying to figure out last night. Turning Particles into packed primitives and then having them interact with my previous setup. 

My way of navigating Houdini so far is to learn something singularly, then see it play it nicely with another aspect. Thanks for the thread link!

[mstarktv]

So I hit another roadblock. I am able to mesh the particles no problem by using the object name on the DOP "Object Merge" tab. Now the problem I'm having is that inside that DOP network I have a static objet, the mentioned POP group that is meshed with the Copy SOP, and now the Pack Geo from the posted technique above.

The problem is that the Object Merge is meshing the particles, but now the Rigid Body Packed particles aren't showing. I have a hunch that I need to somehow add another Object name and then merge the 2 groups after, possibly? The problem is that I don't know how to access the second object name that i created, and I'm pretty sure the Copy Sop ends up meshing both the POP group AND the Packed Group. 

[mestela]

on that object merge tab of the dopnet, use the little + to add a new field, and enter the name of the other object. That, or rename your dop objects to share a common name, and use a wildcard to export them both out.

 

[Farmfield]

16 hours ago, mstarktv said:

WELL THANKS FOR NOTHING JOHNNY! 

I hadn't messed with the instance thing before and I concluded it either sucked or I didn't get the point, so I kinda dismissed it and closed the scene, hehe...

As far as I've taken this type of setup, I always used the copy SOP, often with packed prim's, it's just a great solution. I might revisit the instancing down the line if I run into a situation where that kinda setup gives me issues.

Quote

But no, that's what I did. I'm glued to the help file.

Well, as long as you didn't glue yourself, to yourself, it's all fine.

[mstarktv]

I should have posted my file before. What I'm confused about you'll see in my DOP network. I'm not trying to output 2 POP streams and then merge them. What I'm trying to do is this: 

• Inside the DOP network, have a RigidBody Sim that uses packed geo plugged into the DOP network. 
• Inside the same network, have a regular POP stream that is colliding with the above Rigid Bodies.
• Outside of the DOP network, have the packed Geo appear as it did in the DOP, but then use a Copy Sop to mesh only the POP particles.

My file probably shows it better. It's going to through an error because it's using the read node to read in random files for meshing.  I replaced my read node with a torus. If you go into the DOP network(in RED), you will see particles and the polygonal spheres. What I'm trying to do, is outside of the DOP network, have the polygon spheres have proper RigidBody collisions, while the particles also collide too, but they are meshed(in this example) with the torus. 

So outside the DOP network you would see spheres and toruses instead of just toruses like you do now when you go outside that DOP network. 

I have an idea of how I could get it to work by making a separate DOP network - but I don't want to get ahead of myself. I'm just trying to get my bearings and see if there is a way to do it all through a single DOP network. I think the file will help clarify things.

Thanks, guys!

 

POP_SHAPES.hipnc

 

***update***
Okay, so I think I figured it out. I added an object merge and  then selected the RigidBody Solver as the object to be merged: 

This may be incorrect - but I feel like it isn't in that it works like everything else in Houdini(this just clicked) because just like selecting a SOP object to use in a simulation, this is doing the same thing outside of it. I also didn't even realize that adding the "name" in the DOP object merge, would basically output only that group. This seems to make sense now.

Edited April 28, 2016 by mstarktv
Solution found.

[mestela]

Try this...

POP_SHAPES_extract.hipnc

 

[Farmfield]

In my experience, the idea of keeping things in one DOP - unless you need things to interact both ways - most of the time, it's really isn't a beneficial workflow. The thing is, you really have no benefit keeping stuff in one DOP, instead you'll often end up getting a rats nest and if you turn the setup over to someone else - or even opening it yourself, after a couple of months - it's gonna be tricky to figure out the mindset used to build it. So don't be afraid to stack DOP's (or POPs), it's often a better - or at least not a "wrong" way to do things. And as I know you (like me), Michael, know TP, think about it like this, stacking POP's isn't that unlike how TP works - imagine each stacked POP as a TP event.  

Here's a setup I did stacking POPs, pretty early in my Houdini transition, so there's some "inefficient" stuff in there too, but it's a good illustration for stacking POPs.

Scene file: https://www.dropbox.com/s/9v32xc3hvyw7f9a/growth.v3.hiplc

[mstarktv]

Yes Yes Yes! This is one of the things I've been wondering as a whole with Houdini that you just answered. I've been looking at it and unsure if that is the proper workflow. Relating it back to TP - you would only need 1 in the scene and create groups within. Same with Pflow, just make multiple events. I guess it's good to look at it the way you said. That takes a lot of pressure off. Now I just have to learn how to handle passing data between each and I'll have taken another step forward.

It's funny, the way I look at Houdini is this mishmash of TP/Pflow/Magma/Nuke as far as how things work - not even in an FX capacity. I'm starting to look at Houdini the same way I did when I started using Thinking Particles at Pixomondo. Of course everything I'm saying here is obvious to you guys, but I think one of my favorite things is being able to promote a parameter anywhere. 

Now to pick apart your scene, Johnny...

[mstarktv]

Out of curiosity, I tried adding a Voronoi Fracture Configurable Object into my setup with the bouncing spheres. They will not fracture. But in my other file (I'll post it) they do fracture. Any ideas as to why? The first file is the working fractures, the second is not. Hmm 

noise_start.hipnc

POP_SHAPES.hipnc

[Farmfield]

8 hours ago, mstarktv said:

Yes Yes Yes! This is one of the things I've been wondering as a whole with Houdini that you just answered. I've been looking at it and unsure if that is the proper workflow. Relating it back to TP - you would only need 1 in the scene and create groups within. Same with Pflow, just make multiple events. I guess it's good to look at it the way you said. That takes a lot of pressure off. Now I just have to learn how to handle passing data between each and I'll have taken another step forward.

Yeah, it's funny how you automatically jump to the conclusion keeping everything in one DOP (or SOP!) when it's often beneficial to split things up, layer them, so to speak. Now, this is of course a matter of taste as well, or what works in regard to how you solve problems - but there are no right and wrong in Houdini, it's more about the possibility that there might be simpler ways to do something, or a more optimized way...

8 hours ago, mstarktv said:

It's funny, the way I look at Houdini is this mishmash of TP/Pflow/Magma/Nuke as far as how things work - not even in an FX capacity. I'm starting to look at Houdini the same way I did when I started using Thinking Particles at Pixomondo. Of course everything I'm saying here is obvious to you guys, but I think one of my favorite things is being able to promote a parameter anywhere. 

Now to pick apart your scene, Johnny...

I'm currently writing a piece for Gridmarkets on my aha-moments, getting into Houdini, and how they changed my approach to solving problems. In a way Houdini is very similar to a particle system as it's based on point (or "datapoint", looking to edges, prims or voxels) manipulation rather than mesh/object manipulation. When you get into that mindset, looking at an object as a collection of it's parts rather than it's whole, everything becomes so much easier.

And about my setup, just remember it was one of my early ones, so there's likely some pretty inefficient solutions in there too - but the workflow, stacking POPs, is very useful.

 

 

[mstarktv]

Now thing I noticed was that you converted your sphere to a VDB object for our particles to cling to. What was your reasoning for this? Is it just faster and more efficient to do this to use as a "proxy" object? 

[Farmfield]

There's a couple of ways to get particles to stick to a surface in Houdini, one of them is using the volume density and gradient (direction of density) - you measure the density at the particle position, then push the particle in the direction of the gradient with that value, thus getting it to the closest surface point. 

But you can do some really fun stuff with it too, like this setup where I use the same technique to do mesh intersection avoidance - or what the hell you would call it...

mesh.intersections.hip

And this is just a proof of concept setup, haven't tweaked it much - I got the idea and just tested if it would work - and it kinda did. Fun stuff!

Edited April 30, 2016 by Farmfield