Houdini 18.5 User Highlights: KineFX and Chain SOP

Adam Swaab talked about his experience with Houdini and the new features of the latest software version as well as shared the process of creating the splash screen of Houdini 18.5 for SideFX and educational resources including his own tutorials on Chain and Path Deform SOPs.

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I’m Adam Swaab, and I’m a bit of a jack-of-all-trades. I’ve been in the motion design field for around 20 years. I started out as an animator, worked my way into CG Supervisor roles, and then spent nine years as a Creative Director for a design/post-production company, Wolf & Crow, where we created spots and campaigns for big brands like Apple, Nike, Google, and Honda. At the moment, I’m a freelance CG Artist/Creative Director. Most recently, I’ve worked with Method and FrameStore, but in the past, I’ve also worked for large companies like Prologue, Blur, and Digital Domain. Most of my experience has been in commercials, but I’ve also contributed to the occasional film project, such as Tron Legacy, Twilight: Breaking Dawn, Battleship, Mission Impossible: Ghost Protocol, and Pan. My formal education (many years ago) is in live-action filmmaking, from Rhode Island School of Design, where I also did some study of design and traditional art. I’m entirely self-taught as a CG artist.

Discovering Houdini

I was introduced to Houdini many years ago by a colleague at Blur (Craig Brown). He sang its praises quite strongly for FX work. As soon as it first became available for the Mac (and with the Apprentice version for free learning) I dived right in. It took a bit before I felt comfortable. It was quite different from what I had known in 3D in the past (Cinema 4D and 3ds Max). At that time, there were very few online learning resources for Houdini, and I found some great content by 3D Buzz (Peter Claes’s content, in particular, was amazing) that really helped to ground my understanding of the software. The early days of learning were simply grappling with the software and trying to get it to replicate some of my simpler setups from Cinema 4D. I gleaned a lot from online forums such as OdForce and the SideFX, which were absolutely invaluable. And the rest has been a lot of personal exploration. Fortunately, the tutorial and online learning paths have really opened up in the last few years, and there’s an abundance of excellent content out there now for learning Houdini, such as Steven Knipping’s and Rebelway’s stuff, which I think is amazing.

Advantages of the Software

One thing I loved about Houdini from the beginning is the procedural nature of the software. Coming from a design background, I love to iterate on concepts and test out new things. Houdini was great for allowing me to make a process as part of a design, and be able to play with things like the base elements that fed into that process. It’s a different mindset to get into, but it is one of the things I absolutely love about the software. The other thing that makes it perfect for me is the sheer comprehensiveness and quality of the software. Everything I need is in it, without plugins (full disclaimer, I use GPU render engines instead of Mantra), so I can easily add smoke, fluids, cloth, etc. to all my procedural work, without having to bring in 3rd party software.

Houdini 18.5 Highlights

Probably, the biggest of the new tools is KineFX, which is absolutely amazing, but quite nascent. KineFX moves the entire rigging context into SOPs, rather than object space. It allows any operation that can be done on points to also be done on KineFX joints. This makes it extremely easy to work with and create new and interesting types of animation and rigs. At the moment, KineFX is quite stellar for working with motion clips and motion retargeting, which has obvious implications in game dev. The plan is that it will become a full procedural rigging solution, and it should be more feature-rich in future versions. You can already build rigs in it, but there are still some workflow issues that are being developed and enhanced.

There are also new features related to world-building, such as new scatter tools and nodes that can adjust attributes based on proximity, light direction, occlusion, etc. A lot of these tools take things you could already do in Houdini and packed them in really nice and simple user interfaces, which I think will improve the experience of building terrains and exteriors in Houdini.

If pyro is part of your game or workflow, I think the pyro solver improvements will make a big difference, as well as the new sourcing workflow. Speed and user experience seem like they were a really big focus on this latest update.

What Tools Did You Experiment With?

The Chain SOP and Path Deform SOP have so far been my biggest forays into Houdini 18.5. I’ve only scratched the surface with KineFX, and that’s the new feature I’m most excited to play with. Also, the new pyro stuff is on my list. I joined the beta for Houdini 18.5 at the tail end of it, so my time has been a bit limited so far with Houdini 18.5

Most of my current work has focused on vellum and RBDs, both of which are now being done in SOPs, and it has been amazing. My professional work, sadly, is covered by NDAs, so I can’t reveal much, but it has been mainly particle and fluid simulation work.

Chain SOP

Chain SOP and Path Deform are similar tools, in that they both take paths and place objects on them. Path Deform basically deforms an input set of points to align it to a curve. The Chain SOP can take in multiple pieces and lay them out next to each other in a content-aware way, along a path. By content aware, I mean that the SOP understands the bounds of the incoming objects, and as those bounds change, the chain will auto-adapt to keep everything in line. Both SOPs can be used with deforming or rigid pieces, so they are quite flexible. The two SOPs can be used separately or in conjunction, as I show in my tutorial:

The way it works is actually rather simple, from a user perspective. Collect all the pieces you want to be part of the chain, give them each meaningful and unique names, merge them together into one stream, and feed them, along with an input curve, into the Chain SOP. You can then choose from a variety of ways that the SOP will sequence them, as well as choose unique start and end pieces. You can create attributes that mark pieces as being rigid or flexible, or, as I show in my tutorial, pack rigid pieces for a big speed bump while also marking them rigid.

As for what the Chain SOP can be used for, I think there are some initial ideas, but we’ll be surprised to see what users do with it. Initially, it is great for making chains! Items with pieces that need to sit next to each other, be evenly spaced, or linked together are all great candidates for the Chain SOP. For characters, this would be bracelets, necklaces, belts, etc. Scott Keating showed chairs in a movie theater being strung together and adapting to the changing input curves. And in the Houdini example files, there’s a great example of train tracks. So, for game dev, I can see some places in environment production where this could be quite useful.

You can also learn more about the use of Chain and Path Deform SOPs in the tutorial series Houdini Friendship Bracelet.

Working on the Splash Screen of Houdini 18.5

First, I'll start by saying that having the opportunity to work on this splash image was totally monumental and intimidating for me. A lot of the work I do is somewhat disposable. I make it and then I don't see much of it after it is done. But, this is something I'll be looking at every day for the next year, and the entire Houdini community will be, as well.

The process of creating the image/movies was quite rapid. Fianna Wong – Technical Marketing Lead at SideFX – and I had some great creative discussions about what we wanted out of the image. It was meant to hint at new KineFX features in a completely abstract way. We wanted to work with an abstraction of lines. Lines are everywhere in KineFX – from joint hierarchies to motion curves to animation in the graph editor. We also wanted to go fairly dark and sparse in our visual language. Fianna brought some references to the discussion before we even got started. I played off that and passed a few more back to her. We aligned on a vision for the design, and then I jumped in and started making things. Initially, I wanted to do some rough sketches of two ideas to see what was sticking or what we should abandon. We both were liking one direction more than the other and made a plan to go down that path. From there, it was a few iterations, building toward a still image, but always thinking about motion in the back of my head, since I knew collateral video images were needed.

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Once we had internal approval from SideFX for the splash (a tense feeling for sure, waiting on that), I simulated the rest of the motion pieces output two versions for SideFX – the all-black one in the splash image, and one with gold threads interspersed in it. Both Fianna and I liked the gold version a bit better, but for the splash, the SideFX team, as a whole, wanted to rightly keep eyes and focus on the text. The gold version lived on in the launch presentation and can be seen in several places on the SideFX website. This was an absolutely incredible experience, and I'm so proud and humbled to have been a part of it.

Learning Houdini: Where to Start

Probably the best way to get started right now is to go through the official SideFX learning materials first. The basic 5-10 minutes videos are great for getting you up to speed and working quickly. I absolutely love their masterclasses for more advanced concepts and deeper understanding of new nodes and techniques. I’d love to plug my own stuff here, but most of my content is in need of a refresh, so it will be a bit before I have up-to-date learning materials available.

I also mentioned Steven Knipping above, and I stand by that. He’s really good, thorough, and easy to follow. I haven’t watched Mark Fancher’s series, but the promos look great, and he’s a top-notch artist, so they are certainly worth checking out. Entagma is always full of interesting techniques and knowledge. For games-specific content, Simon Verstraete and Paul Ambrosiussen (Paul of the SideFX Labs team) both publish a lot of great stuff. Matt Estela’s blog, CG Wiki, is a world-class resource, incredibly well-explained and filled with probably hundreds of helpful gifs.

Adam Swaab, Creative Director/VFX Artist

Interview conducted by Arti Sergeev

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