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​Featured Artist: Tim Sepulveda, Chicago

​I am Tim Sepulveda, FX Technical Director based in Chicago. I love working with Houdini and have used the software throughout my career. I hope you enjoy my fur tutorial!

Art has been a constant in my life for as long as I can remember. When I was seven or eight years old, I would sit in front of the TV and draw ghostbusters and transformers, fascinated by the shapes and colors flickering on the screen. When a friend at school signed up for an art summer camp I insisted on going as well. So my parents signed me up. From then on, art camp was the highlight of the summer.
In High School I accelerated my development in the arts, mainly thanks to the strong influence of my high school art teacher. He introduced me to digital arts and, thanks to him, I got my hands on my first Wacom tablet. In those times tutorials were hard to come by and we’d get excited designing a fork with our computers! However, precisely because digital art was in its infancy art schools also didn’t bother coming to my College Night events.
I finally resolved that my passion for the field had no future. So after graduating from high school in 1999, instead of getting an art degree, I enrolled in automotive school, in an attempt to channel my interest in cars and hotrods. In a way you can’t force things though, so after two years in automotive school I said to myself: “That’s it! I can’t do this – I HAVE to go to art school!” I hopped into my car, drove up to the Illinois Institute of Art, walked up to Admissions with my portfolio in hand and asked: “What do I need to do to get in?” The admissions officer eyed my portfolio and asked: “Want to start tonight?” That was the beginning of an amazing three and a half years of awesome art education.
People think that art is easy, that getting a fine arts degree involves no real effort. Nothing could be further from the truth! You get out of art school what you put in. I had a group of friends that felt the same: We’d stay in the computer labs until late at night working on our projects, we’d go to the movies together just to study how effects were done. We’d push ourselves creatively every day. I blasted through college in three and a half years and didn’t bother taking the summer off. I enjoyed the experience immensely. After graduating from college in 2005, I had a bit of a rude awakening though, because searching for a job wasn’t as easy as I had thought. In fact it was downright tough! It was difficult for me to find my core skills and identity as an artist and nearly impossible to accept that I couldn’t be good at everything. I forced myself to take a long hard look at my portfolio and resolved to throw it all out the window and start from scratch. I spent six months studying old Digital Domain materials to improve my skills and reworked my entire portfolio; then I set out to aggressively look for a job. Soon after, Chicago-based Radar Studios would offer me my first position – they made it clear that if I wanted the opportunity I’d have to really want it, really fight for it. And so I went for the challenge and ended up staying for two amazing years doing many short projects for huge brands such as McDonald's, Nintendo, Hasbro and Nickelodeon.
But as is the case with most artists I eventually got the itch to go and try for something more challenging. But what was my next goal going to be exactly? Shortly after asking myself that difficult question I got a call from a recruiter. Amazingly she remembered my work from my college’s digital arts festivals. “So, Tim,” she probed “have you ever thought about moving to either coast to work?” This question caught me off guard, but I quickly recovered and enthusiastically declared that I would love to move to either coast. I figured that if I didn’t try moving then I likely never would and I’d just be content plodding along.
Shortly after this pivotal conversation I started interviewing with several studios on the East coast. I remember thinking that I might as well tackle New York while I was at it! One of the last places I visited there was Charlex, a VFX powerhouse that has been around since the late 70’s - and remarkably I got myself hired! I was super nervous to come on board, thinking that I did not know enough to work there. Eventually I resolved to just be myself and do what I do best, which is to churn out great work. Within a couple weeks I was actually promoted to Assistant Creative Director, which gave me an amazing feeling of accomplishment. Charlex was a very intense place to work at both creatively and technically. We did huge jobs and small jobs, so learning the ins and outs of who does what was really important. My 3D background allowed me to be able to assist the 3D team in client pitches, most importantly by bridging the gap between creative and technical requirements in order to get the job done. Charlex definitely had one of the strongest and most talented teams I had ever worked with in the industry. Lots of fun late nights and lots of great friendships developed that still exist to this day.
After staying in NYC for a while I decided to come back home to Chicago; I guess that sometimes you just can’t escape the need to be “home”. When I got back to my home turf a couple of old coworkers and friends were forming a new shop called Leviathan, so I decided to hop on board with them as their VFX Director. At Leviathan we had the privilege of working on some extremely cool and ground breaking projects for Amon Tobin and his ISAM tour. ISAM was one of the first if not the first truly successful projection mapped concert experience. I got to work on 2-3 songs for their huge stage show. The first song was about 7 minutes of content, combining smoke fluid sims and a monster After Effects project. After the success of ISAM we did some smaller projection projects for Drake, and Skrillex. These were not as intense and combined more element creation and FX, but they were just as good visually. We eventually worked on the version 2.0 of the Amon Tobin tour as well: The stage was even bigger and lead to plenty of new challenges for the VFX teams. We learned to build a very different workflow and in the process we figured out which effects work, which fail, where the limits are and lastly how we could apply our newfound knowledge to commercial work. 
From Leviathan I transitioned over to a position as Technical Director for Vitamin Pictures, a Chicago based creative studio. I enjoyed working there because everyone was very passionate about what they did and it definitely showed in the work. Vitamin was the first place I felt comfortable really bringing Houdini "up to bat" as they say. It's always a scary thing for a studio of any size to be receptive to a new piece of software. At Vitamin I solved this problem by integrating Houdini bit by bit. I started introducing small elements such as smoke or particles that people usually pigeonhole Houdini into, so that everyone could see what could be done to solve specific creative problems. My ultimate goal however was to show the team the power of Houdini, from fluid sims, to lighting / rendering, and everything else inbetween. I did a LOT of R&D whenever possible to demonstrate the versatility of the software, which resulted in 100 hip files of just miscellaneous effects and techniques. You can see some of this work on my Vimeo page, although I'm still far behind on updating it. Eventually massive portions of the last jobs at Vitamin were all Houdini and Mantra based. As timing has it this is also when I saw the first small advertisements for GridMarkets. We were working on a scene for a spot that involved FULL cg volumetric clouds with character and lighting interaction. Our local farm here was swamped with renders from the Maya artists, so I had to make sure my stuff completed on time, if not before. GridMarkets helped me hit the mark at a price that the producers were very pleased with, which is always super important. So overall I think I got the team at Vitamin to see the potential for Houdini. Going forward Vitamin won’t need purchase plugins left and right, as I've had to do in the past for studios using other software packages.
My next career move is going to be an interesting one, so stay tuned. I think it's very important to know what you're good at as a digital artist, and focus your power there, be it animation, VFX or lighting. Really know your stuff! I will continue working as a Houdini artist, trying to always push the creative side to show people that Houdini is not just a "effects" package, but that it can be used for every aspect of a pipeline. I'm super excited to see what the future brings for Houdini and all of the artists that use it daily! And here I would like to say a huge thank you to SideFX for making such a great software package, and having top-notch support for all artists regardless of studio size. Also, thanks to everyone at GridMarkets for your support and great render farm accessibility. 

Tutorial: Making the fuzzy fuzz

​Not many people know this (well, now they do), but I make felted wool characters on the side for fun. It's a weird hobby, but one that relieves stress and allows me to take a break from staring at a computer for hours on end. One day we had to do a pitch for handmade characters and I was like: “Huh, I'll just make one by hand, why not?” Everyone loved the quirkiness of the pieces, and asked, "How do we animate one of these?" Hmm... good question. The Maya team went off to try and create a style using various tools and plugins. I hadn't really touched the Houdini Fur system a lot, and I know that most of the training was focused on fur for long haired creatures, grass and such. So I decided to take a long look at each parameter with the goal of finding a "fast" combo of settings and techniques, so that I could crank out a consistent look time and time again. Here is a small "tutorial" of what I came up with. At the end I will show you some examples of the various uses I have found for my Houdini hair system. Remember, this tutorial focuses more on the fur system and less on the lighting and rendering aspects, which are also important to optimally present fur.

​Starting off, I create a standard sphere, simple enough. I like always having objects with uvs on them, so I can use the same texture on the hair system and on the "skin" object. This allows the color to be boosted a hair (no pun intended) in both the geo and the hair. Also it helps hide some small bald spots here and there…

I also like to add a NULL to the bottom of the tree just so I have a place to point the fur to directly.

Tutorial: Making the fuzzy fuzz: Creation of a standard sphere

​I do not like using a lot of the shelf tools. They are great if you want to learn what goes where and why, but I suggest doing the 'ol TAB > search for "fur" and add that. Once you have that under the SKIN tab,  make sure you choose the geo that you want to use as your fur object / driver. Either point to that NULL you created or just point to the main geo. Keep in mind that if you have any groups destined to be areas for fur, you can point to those right below the SKIN selection in the GROUPS selection. 

Choose the geo that you want to use as your fur object / driver.

​Cool, we have fur! It's lovely default brown at the moment, so let's change that. On the BASIC tab on the bottom is the Material selection. Let's jump into the "textured_hair" material.

Let's jump into the "textured_hair" material.

​Lots of boxes will be ticked and not look like the photo I have here. First make sure the DIFFUSE INTENSITY is at 1.0, to ensure that the texture map is at full intensity. Next change ROOT COLOR to white. You can play with this to tint the hair color a bit, but if you want the texture map to come through go white. Next check USE MAP, obviously to use the created texture map on the geo.  Tick TIP COLOR, WHITE HAIRS , and GUARD HAIRS all off for the time being. 

First make sure the DIFFUSE INTENSITY is at 1.0

​On the Hair_Shader OPACITY tab, make sure you adjust the opacity ramp to what you want. I like things to be mostly solid, as it will make it easier to achieve the "wool look".

Adjust the Hair_Shader OPACITY tab

​Go back out to the main level of the FUR and onto the GUIDES tab. Here I boost that number up to about 1000, mostly to get a decent coverage all over the object. Remember this is dependant on the object and scene scale. The more guides the more the actual fur curves have to use as a "driver".  Upping the RELAX ITERATIONS value also helps keep the spread of the guides really even, avoiding the "bald spots" as I call them. It also doesn't hurt to increase the SEGMENTS a bit. This will help increase the visibility of any noise and roughness we introduce.

Get a decent coverage all over the object.

​Moving onto the APPEARANCE tab we start to really build the look of the fur with all these controls. As for LENGTH and DENSITY I usually just make sure the RANDOMIZE LENGTH number is really high; this is personal preference of course. I will always play with this number to find a mix of too random or too similar. 

​Moving onto the APPEARANCE tab we start to really build the look of the fur.

​With regard to the THICKNESS tab, I just make sure that the MAXIMUM THICKNESS value is small or in other words thin. Once again this is all scene and scale based. Wool fibers are crazy thin. It's a careful balance between a physical accuracy and a "it looks right" balance. Remember, the thinner the strands the more render adjustments you're going to need to make them look good. Also, playing with the THICKNESS spline ramp is a great way to change the shape of the strands a bit. For wool I just like a nice ramp. Once again, this is just a visual preference. 

The MAXIMUM THICKNESS value is small or in other words thin.

​Let’s talk about the FRIZZ tab. This is a big one, as things can go from looking like a well groomed sleek ball of fur to a messy fake looking cg hair clump in seconds. Of course you can see your hair update in the viewport, so always keep an eye on that! Going about half-way on the AMPLITUDE MAX value really makes things start to separate and pull the strands apart just enough that you start to get a bit of a handmade look going. But be careful with this number! FREQUENCY pushes the FUR curves into an "S" curve, while ROUGHNESS causes more "harshness" to that "S" curve in the strands. 

FREQUENCY pushes the FUR curves into an "S" curve, while ROUGHNESS causes more "harshness" to that "S" curve in the strands.

​CLUMPS... This is the tab that made me have a huge aha moment one day. Clumps in Houdini cause groups of hair to come together at the tip, if you leave the Clump Profile standard. The cool thing is that if you look at the effect this creates, it almost looks like a bird's plumage and the associated feather patterns. By increasing the DENSITY number you allow more groups of stands to clump together. There is no magic number to this; it is a careful balance with length and overall density. The TIGHTNESS parameter is what does the, well, tightening at the tip, or wherever your Profile curve enforces. To get that feather look go towards the upper limit, but never the whole way. I like the small variations that occur when not fully at 1.0.

Clumps in Houdini cause groups of hair to come together.

​A quick note about lighting fur: For this brief tutorial, I set up an Environmental light with an HDR driving the overall color and fill, and one Area light creating a side hi-light and a bit of a small back light, which always makes fur "pop". 

Lighting fur

​Lets kick off a preliminary render here. First though let's jack up the RENDER DENSITY, maybe to about 100,000. This number is scale / scene based also. The Fur Thickness is also really important to monitor when rendering. Take a look at that render! You should see the groups of fur clumping together. This will look almost like those felt poof balls you see at craft stores. Good start, but we need to add a little more work to this setup. 


​This portion I do not take any credit for, that honor goes to David Pekarek.  I recommend doing any fast grooming this way for one reason: It allows you to readjust certain values very fast, such as overall length and guide count. Those are 2 things I find myself going back to time and time again. Yes there are ways to do what follows with the shelf tools, but for fast coverage with lots of flexibility I really like this method. So let me show you how to do this easily. Right click the FUR node, and go to "Allow Editing of Contents", and dive inside the FUR node. 

 I do not take any credit for, that honor goes to David Pekarek

​Don't get scared, just proceed and dive into the "apply_display_offset" node.

Dive into the "apply_display_offset" node.

​In here go ahead and add an attribute VOP. 

Add an attribute VOP.

​In the VOP create two CROSS PRODUCT nodes, a MULTIPLY node, and a ROTATE node. Connect them as shown in the pic. I won't go into detail, but basically hair grooming is controlled by the point normals. You can click the "view point normals" button to see what has happened. They all point up towards the sky. It’s instant grooming, kind of. In your first CROSS PRODUCT node, changing the VECTOR2 values will control the overall direction of the hair. I made mine -1, so it goes down for this tutorial. 

​In the VOP create two CROSS PRODUCT nodes, a MULTIPLY node, and a ROTATE node.

​Next in the ROTATE node, change that ANGLE value. You'll see the point normals update in the viewport. I like to get this so none of them interpenetrate the surface.

In the ROTATE node, change that ANGLE value.

​Back out of the VOP and now add a COMB node below it. 

Add a COMB node below it.

​This will now allow you to really groom the direction, specifically of the normals. It's not as great as combing the guide curves, BUT it's really fast. Also be sure to have the COMB LIFT value higher than "0", otherwise you're pushing the normals back into the surface and hair will be inside the geo creating bald spots. I like using the COMB LIFT with small values to create a "matted" look on a lot of my furry objects. Once again we're shooting for a "hand made" looking object. 

We're shooting for a "hand made" looking object.

​Once again let's render this one. Now that looks pretty cool, the hair is clumping like feather bunches, and yes, it flowing with our point normals! This is so much better than throwing hair on an object, doing some minor grooming and calling it done!

Let's render!

​These are some more renders with the exact same fur setup. You can see how "re-combing" the normals can lead to some really cool outcomes, from a weird felted bird texture, to a matted ball of fuzz. However, I cannot emphasize enough how much good lighting can help or kill a render of fur in the end! I'll attach some other examples of things I have done using these stupidly simple techniques. In the end the results from the Houdini fur system gave me an edge over some other techniques that were done in house, once again helping to push Houdini as a tool for EVERYTHING, not just particles!

These are some more renders with the exact same fur setup. "re-combing" the normals can lead to some really cool outcomes.
Tim Sepulveda 2016


By: Patricia Cornet
GridMarkets marketing

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