Watchmen In this interview Kevin Hudson will share his workflow of using scanned data in ZBrush for "The Watchmen".

The ZBrush Team is proud to bring you a behind the scenes interview with Kevin Hudson on his work in this spring's major motion picture, "The Watchmen". In this interview Kevin will share his workflow of using scanned data in ZBrush to capture the detail of actor Billy Crudup, who played Dr. Manhattan. he will also walk us through how he created the terrain of Mars for the movie.

Kevin Hudson will also share some unique ideas of how to use ZBrush to sculpt freely, quickly, and with no limitations.

I got involved with "Watchmen" immediately after I finished "I Am Legend". For "I Am Legend" I had built a bunch of muscle zombie creatures in ZBrush. I saw "Watchmen" as a chance to take a lot of what I had learned on "I Am Legend" and refine it. In some ways, it would be a chance to do Volume 2 of something I'd just done, and do it better and faster. ZBrush had come a long way in its ability to sample scan data and extract high res details and then reapply it to a base mesh.

"Watchmen" enabled me to work with a team of people, most of whom I'd had the chance to work with in the past, again. What's great is when a team comes together and really functions. Elbert Yen came on as the texture artist for "Watchmen", and he was the main texture artist on "I Am Legend." We really enjoyed working together, and since I knew I would be doing most of the sculpting and detailing in ZBrush, I felt fortunate to have someone on the texture end of things that was familiar with what I would be handing off to texturing. I see the displacements I create as the starting point for texture painting. They are not necessarily the final textures.

The overall workflow began with scan data of the actor who performed Dr. Manhattan, Billy Crudup, and a bodybuilder who was the body double, Greg Plitt. Billy's head was scanned, and Greg's body, hands and feet were scanned separately. Once I'd created the rough mesh from another application of Doc using portions from the various scans, I took the mesh into ZBrush, subdivided it a few times and then used the projection tools to extract more details from the scan data. I had to do it in pieces and then export out maps for each piece. I then reapplied each displacement map to the model until I had the detail from the scans roughed in on the entire model. I then began the sculpting phase. Doc looks somewhat like the source material, but he's much more exaggerated in detail than what could be derived from simply scanning.

I could do a projection of a subdivided mesh onto the scan data, and it would only take minutes. There were a lot of other hurdles that I would have to do as well. When I did the projection on "I Am Legend", the model would lose its UV's, and it would get reordered. I'd have to reconstruct the mesh back down to the base level, and then export the mesh back to Maya to restore the UV's. This was complicated by the fact that when I would reconstruct back down to the base level, I would lose the Vertex order, and I would have to copy the UV's back to the model based on this new vertex order. Now, however, it is simply a button push, and all of the UVs and the vertex order are maintained.

I had multiple scans (head, body, hands, and feet), I needed to do the data extraction on the model on each of the scans. In order to speed up the extraction, I broke my master model up into the same different pieces. After doing the projection on each piece, I would export out the displacement information as a map. I then brought in the master model, and displaced the geometry on the master model with each of the exported maps. Because the map is neutral gray where there isn't displacement, no displacement occurred on any part of the model other than the part that was displaced. Once I displaced all of the different maps, I had a complete model with the displacement from each of the scans applied to my master model.

At this point, I was free to start re-sculpting and enhancing the model. The important thing to realize with any project that involves a lot of scan data is that the scan data is just the starting off point. Dr. Manhattan, though similar to Billy Crudup and Greg Plitt, looked very different when finished. He has proportions that are classically heroic and taken to greater levels. His legs are longer, and his shoulders are huge. His waist is leaner. All of this was done to create the impression of his strength and power.

I used the rake tool a bit when I was cleaning up the seams between the different scans. I found that I could even out a surface, much the way I did in clay when I was a more traditional artist. There were places where I needed to create the finer pore detail. When Billy was scanned, the scanner picked up his eyebrows, and I raked these away, and then smoothed them out.

But this was then an area that had no pore detail. We had some great close-up photography of Billy's face, so I took some of that photographic detail, and created a pore texture to use as an alpha in ZBrush. I was then able to reapply the pores to the area where the detail was missing. This worked very well, and it was Billy's pores. I used a similar trick at the seams on his neck, wrists and his feet. The top of his head also needed some simple pore texture so that it wouldn't look strange.

For the veins, I used the clay tool to build some nice veins. The veins were a design issue that I fought for. At one point it was felt that since he is made up of energy, he would not have any veins. I explained that veins emphasize power and flow. As we wanted to have energy flowing around inside him, this went along with that concept. They are also great design features that show his strength.

I'm not involved with these decisions, but as Doc Manhattan represents man's concept of ideal man, it makes sense that it be an artist interpretation of a male as opposed to being a male. Certain body parts have been exaggerated -- shoulders are wider than normal, his waist is smaller, his legs are longer, and he walks around naked for most of the film. Once everyone got used to the idea that we were doing digital full-frontal male nudity in our film, it was fine. It did take some getting used to, and made for some awkward dailies at first.

For the energy running under the skin. I built a series of curves that mimic not only the veins and nervous system of the body, but also the directional flow of the muscle fibers. The curves were then handed over to the big brain dynamics/rendering people who worked their magic. They used caustics, and somehow ran energy along these curves. It was amazing the first time I got to see it working. Those guys are amazing. Likewise, Elbert Yen, who was the texture painter, is amazing. He took the displacement maps that I exported out of ZBrush, and used these as a jumping off point for the final maps. I had worked with Elbert on "I AM LEGEND," and there was such a trust between us, and that is the most important thing in production.

One thing I've learned over the years is that this job is all about teamwork. I'm pretty darn good at what I do, but I don't know everything. I've learned that I don't have to learn how to do everything, as long as I have trusted collaborators who are really good at what they do.

The initial build on Dr. Manhattan was approximately 2 weeks. However, that was just the beginning. Once he got into animation, there were additional revisions, and then when he got into rendering, there were some more additional changes. He was fairly simple in regards to the number of subtools needed for him. As he's naked most of the time, there was a body subtool, a finger and toenail subtool, an eye subtool, and eventually what we called the "battle shorts" subtool.

For the smiley face crater, I started with a great photo that I found on the internet of the crater. I found myself using the Alpha Palette settings such as Blur, Flip Right & Left, Intensity, and Radial in ZBrush which will create several different alphas from one image. I then used this as a displacement map to quickly rough-in the model. I then cleaned this up, and that became the basis of the model. Of course the redesigning of the crater then began. There was considerable back and forth about how much the crater should be a smiling face, and how much was too much.

Like a lot of things in this business, the model I built then became the basis for a Matte Painting, and my initial model was discarded. I then used the matte painting as the basis for me to sculpt some rough supporting geometry so that the painting could be reprojected onto that version of the model. However, it was interesting to be able to use an image from the internet as a means for quickly creating geometry.

We also had some great imagery from the Mars Lander that I used as the basis to create alphas that I could use with ZBrush's sculpting tools to sculpt the different landscapes. These images were also great inspiration for coming up with the features that are seen in the models. There are some really cool craters that I tried to put into every environment. Otherwise, I was worried that they would look too much like the Santa Fe desert images that were also very much the inspirations for the environment. It's amazing how otherworldly our own world can look at times.

There are several moments that I love in the movie with Doc. I love the shot where he is working on his reactors. I built the reactors and all of the pieces that he has flying around, so that makes me proud to see both my character and Hard Surface work in a single shot.

I also love the shot where Dr. Manhattan is in Vietnam blowing up people. When I was in film school at UCLA, many, many years ago, I did a Vietnam film. When I was doing traditional effects, I built some human dummy's that got blown up. I had to call my old boss to tell him that here it is almost 20 years later, and I'm still blowing up people. The exploding people were a lot of work as they wanted to see bone and guts. Those shots are very nasty and fun.

Bubastas, the tiger lynx character, is a great example of how a model can be modified from one project and turned into a new character for another. I'd built a lion character for a previous film, and then by using Maya and ZBrush, I was able to re-proportion it and re-sculpt it to be the Bubastas model for Watchmen. The initial build phase for this character was only about a week.

One thing to remember is that Doc looks good because he is the result of doing a bunch of initial work studying how ZBrush would fit into a production process. The first use of ZBrush at Sony was on the film Ghost Rider where Kevin Mack and Daniel Kuehn allowed me to bring this as yet untried production tool at Sony to create the flying Zombies at the film's climax. That worked so well, that I built some of the desert landscapes as well as the Wes Bentley, Blackheart, Demon using it.

ZBrush again showed its design power on Spider-Man(tm) 3. I wasn't crewed to that show, but I was called in to sculpt a couple digital maquette ideas. I built 3 basic concepts, and Sam Raimi was better able to visualize what he wanted. I also built several head ideas that went from very human to over the top and down right "Evil Dead-like". He chose the one in the middle, which had no eyes. For this one, and it's nice to see that it made its way into the film, I tried to create the impression that his eyes had eroded out of his head, a metaphor for him losing his soul. I thought this was poetic since that was where his character is in the film.

ZBrush was essential for the infected characters in "I Am Legend". I knew going into that show that ZBrush would be the perfect tool for creating the ultra lean characters from the Alpha male and female to the dogs and rats. All of the variations in the infected characters show the prowess of ZBrush in creating quick alternate design models. I've had great success in a film production environment using ZBrush as part of my modeling pipeline. The key is remembering that ZBrush is just a part of the process and that there is a huge amount of collaboration and teamwork involved in creating the imagery that we create for films.

Thank you Kevin Hudson and Sony Imageworks!