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Interview: “EPIC” Reworking of Blue Sky Studios pipeline with Marin Petrov

With the release of the latest animated feature Epic from Blue Sky Studios, Rigging Dojo brings you an exclusive look behind the scenes on the building a new pipeline for the movie with Marin Petrov

With the release of the latest animated feature “Epic” from Blue Sky Studios, Rigging Dojo brings you an exclusive look behind the scenes on the building a new pipeline for the movie.

Interview: “EPIC” Reworking of Blue Sky Studios pipeline with Marin Petrov


movie poster from the movie EPIC from Blue Sky Studios - from Rigging Dojo Interview with Marin Petrov

Blue Sky Studios has been around working on making characters and beautiful renders since the industry of computer animation started.  We are always excited to talk with artists like Marin who no only do great work they share back with tools or tutorials and grow the community.

I always find it interesting how people got started in to their career since it always is so varied. Can you tell us and our readers a bit about you and your start and path in the industry?

From very young , I have always  been interested in all kinds of art  but at the same time I have always loved playing with technical things and later on with computers. This imminently lead to experimenting with animation and 3D software. I have always been a self learner and everything I have ever learned was either by myself or by directly going to somebody I knew and asking him questions. I am also not a big fan of the school system and I never “studied” something related to animation in the sense that the society thinks is necessary.  If I needed to learn something more on a particular subject I was interested in, I simply read books  or  attended different university courses and lectures on the subject.  Also one of the reasons I don’t like the educational system is that if I was interested in arts , mathematics and music at the same time, I couldn’t study something that deals with all those subjects. And this is why I attended several different university courses , trying to get my hands on subjects I was most interested in.

So at one point I had the skills to do a little short animation project that I used as a demoreel to get into the field. Now looking back into it , the animation looks extremely crappy. I think at that time I was thinking it was good.  I also had worked on several projects as freelancer. I was hired by the biggest visual effects company in Bulgaria at that time and started working as generalist on several feature films. From then on , I really learned a lot of things just by working in the field.

Advice on getting hired from outside the US?

Just apply normally as everybody else. If the studio and the team really likes you and wants to get you onboard,  they will help you get a work visa if you don’t have such. Sometimes the visa process can take some time before you actually start working.

Was there someone or some studio that really helped guide and mentor you when you were getting started?

Worldwide-FX (Sofia, Bulgaria) is the first big studio I worked at. I  developed a lot of knowledge there. Also a coincidence was that I got hired there at the same day as one of the best people I have ever worked with in this industry – Dobri Georgiev (currently a CG sup at WWFX) . From that day we were always sitting next to each other and were working together in solving different problems on improving the pipeline in the studio. I can honestly say I learned a lot from him.

Starting at Blue Sky

I joined Blue Sky Studios at the beginning of 2010. After I sent my demoreel  to them at the beginning of 2009 , I got an interview shortly after , but because of the visa process it took almost an year to get onboard. I almost immediately started working on the new pipeline for “Epic”.

Is there an example of something that was heavy  on the old rigs that didn’t need to be that way or  maybe didn’t need to be in the rig at all?

The only reason to do the rework was the speed issues of the rigs we were having. The rigs had so much potential and flexibility layered that in some cases most of the features were not utilized by animation (for example for a background character) but were slowing the rigs down. So the idea was to simplify the internals without sacrificing the performance of the rig.

Fresh eyes are always great but it can be a challenge dealing with changes to existing established systems.  How was it handled and would you have done it differently now that you have the experience to look back on?

One of the reasons it was not that hard is that we started it from scratch without a single line of code used. Some might argue this is a bad thing to do, but I think in this situation it was the best possible solution,  because it seemed much harder to modify existing systems than to build one from scratch.

In some situations where there are two valid ideas how do you effectively narrow down that decision  process?

Difficult! Most of the time we discuss extensively what would be the best approach, but of course everybody has different opinion about how something should be done. When there are two or more valid decisions and we have time to prototype , try them and evaluate them all , we do it. Most of the times that is not the case because of time constraints and then in discussions everybody tries to come up with good arguments to support his/her idea.

Modular rigging gets a lot of buzz and excitement going but how do you manage those modules once the final rig is built.

Our approach is not exactly 100% modular. We have modular scripts that only install parts , but there is a conglomerate script that combines them and  builds everything together. Once it is built, the whole rig is one big package driving the joints and the deformers

You have a great tutorial and example of a spline ik in Maya that can deal with more than 180 twist, you can manage the spine twist via your custom node, 1 vs. 7 or 8 Maya Math nodes.  Does this mirror your process and experience trying to streamline the rig system via plugins?

Mostly yes. If something can be achieved via writing a plugin, we are trying to go this way. That minimizes the nodes used in the graph, simplifies debugging (most of the time) and speeds the whole rig (most of the time). For the spine that we currently use I wrote a simple plugin that drives some transforms. It is fairly simple solution and the graph does not look cluttered, making it easier to evaluate and debug.

You mentioned to me that the goal with the new rig system was to keep the same or similar features to the past systems. Was this so that existing assets could be used still or because the animators were just used to the old rig?

Mostly because of how the animators expected the rig to behave. We didn’t want to introduce new features which would slow the rigs down , neither remove existing ones which they liked. That being said, we went to a process of iterating all our rig solutions and replacing them with new ones.  Of course at the end we ended with quite a few awesome new features which the animators simply love!

Were there any special considerations for having the of “classic” looking 3d characters and realistic creatures and animals, were the rigs different for them or based on the same system in Epic?

“Epic” is slightly more realistic looking movie and the rigs had to be treated a little differently. Some of the rig components we wrote were more suited for realistic type of characters and we have different solutions for the same body parts for more cartoony style characters.


two main characters, male and female from EPIC from Blue Sky Studios - from Rigging Dojo Interview with Marin Petrov
Bomba, a scientist, and his daughter, M. K., become embroiled in the affairs of the Leafmen in “Epic.”

Can you talk about your approach to bone placement and skinning vs. what you do with corrective shapes or helper bones or some other custom deformer system to make things move nicely.

Every rigger here has his own approach of handling deformations. That is one aspect of our job where the TD decides how to handle a particular case. The only thing that is common is the rig that drives the deformers and the joints, but it is up to you to decide how to achieve the art direction of the character. I personally like to handle as much as possible with the skin deformation and joint placement without using any correctives in the first pass. Once I am in a position where it feels ok, I add a second layer of tweaking with corrective shapes. I almost never use helper bones in our system here, although I had used them before in more realistic characters. I just prefer having as little layers and variables as possible. So for me a skin + correctives is enough. Some colleagues like using helper joints.

How does the Blue Sky team distribute work between Modeling and Rigging and Pipeline? Do the Modelers just model or do they also do deformation for example.

Modeling provides us with a character for which we can give feedback of how the edge flow or the overall topology should be. After it is approved they pretty much don’t get involved in the rigging process. We do the deformations via blendshapes and it is up to the character TD to sculpt them. Also if there is pipeline task strongly connected with our department, we are the ones that handle it. Only if it is something that concerns a lot of departments, then the Production Engineering team or RnD team handles it.


main vilian, dark, flying on a bird, with a bow and arrow about to shoot - from the movie titled EPIC from Blue Sky Studios - from Rigging Dojo Interview with Marin Petrov
Mandrake is the leader of the Boggans and the main antagonist of the film “Epic”.

What are your thoughts on finding good TDs to hire, what were you looking for among the reels?

Uniqueness! We are looking to see problems solved in a unique and interesting way.

I was asked this during a panel discussion and really liked the question. What Thoughts or advice would you give to yourself then, knowing what you know now having been through the experience?

Oh I have never looked at my experience from such an angle! I would definitely say something to myself: “Don’t sweat it, just go with the flow. ” But of course now only I know what that means….. saying it to myself… from my future self….. in the present. Erggh.

What would you say the average time spent on the skinning stages are? I know this varies but it is always insightful to compare time spent to finished asset.

This strongly varies on the performance time of your character. If it is a lead character , it takes a lot of time to get it final. We have 3 stages of iteration here and we communicate with animation not only at the end of every stage, but also while working on it. This helps tremendously in knowing what to expect and what to hit. The first step is usually getting the joint placements and the skinning right. We also do some basic blendshapes in the face just to mark them down. At the end of that phase,  usually the lead animator assigned for your character,  is given some time to evaluate it and give you feedback. In the next stage we try to hit the notes from animation and also add all the correctives and mostly all the blendshapes in the face. Once finished,  the animation department have the chance to give you another batch of notes. The third phase is usually the polishing one where we fix all the notes given to us and polish everything. As I said , while working on every stage,  you have weekly meetings with animation to discuss your work in progress and maybe give you notes before they get the rig for evaluation. For background characters we pretty much have the same schedules, except that the time in every stage is shorter.

Is there a validation process before a rig fix or update gets pushed out,  I am wondering if things change when you get the rig “done” and go in to maintenance mode once animation starts.

Things definitely change once a rig is approved. If you have a note from animation or other department after your rig is finished, then once you fix it and get approval from the leads you can directly push it to the floor. We keep track of every change and version of the rig so it is easy to roll back in emergency situations, but most of the time it is not needed. Very rarely something on the rig interface to animation changes so most of the time the changes are either deformation related or pipeline related.

Do you see any major advancement in rigging for characters in the near future or are the techniques mostly standardized now?

I have been watching closely how the OpenCL / CUDA libraries have been evolving and I think a logical step in our pipeline would be to move some of the calculations to the GPU.  Of course that would require a lot of the basic DG nodes to be rewritten to support parallelism.

Any last tips or advice you can give to someone that wants to improve their skills as a TD?

There are no two TDs with the same set of knowledge, some of us are more technical, some of us are more art oriented. Whatever it is, recognize your strengths and weaknesses and work particularly on improving them. If you want to improve your technical skills, read math. If you want to improve your art skills – draw! It is very unique to everybody so my biggest advice is to recognize yourself and your skills.  I have to admit that sometimes I get scared from tasks I have no idea how to solve, but you don’t need to be. It is extremely pleasing once you solve them.

What do you feel is missing in current TD skills or reels?

Originality and showing problem solving. Most of the rigging reels look quite the same and there are very few that stand out from the crowd. Aesthetics is also missing in a lot of rigging reels I have seen and this is the basics of our job.


of the film Epic.
Mub the slug lets his feelings be known to MK in the 3-D animated fantasy “Epic.”

Last question – what book are you reading right now or last finished?

For some reason I never read only one thing at the same time. Currently I am reading some tech PDFs and papers, a book on linear algebra, “JavaScript: the good parts”, “Business model generation” ,  a book on color theory and a book on UI / UX design.

Thank you so much for taking time to talk with us we are looking forward to seeing Epic when it releases.

It was a real pleasure for me too. Thanks.

To find out more about Marin check out his website and the links.

Thank you once more for your time and sharing such great information with our readers

Josh, Brad and Chad


About Rigging Dojo:

Rigging Dojo is an online training center providing personal and customized character rigging and technical art education. Our services are for artists looking to break into the industry, learn new skills or update existing ones. Our mentors are working industry professionals and are dedicated to training current and future technical artists and riggers to be production ready.

Photo Credits: Blue Sky Studios – TM and © 2013 Twentieth Century Fox Film Corporation. All Rights Reserved.

p.s. Looking for a job with Blue Sky Studios, check out their jobs page, they are hiring for various postings like

One reply on “Interview: “EPIC” Reworking of Blue Sky Studios pipeline with Marin Petrov”

great interview, always great to see what the guys behind the scenes of the big blockbusters are up to studying and how they think.

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