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Strange Magic: Framestore & Doctor Strange VFX

Framestore CG Supervisor Alexis Wajsbrot explores the challenges posed by creating the VFX shots for "Doctor Strange"...

Framestore CG Supervisor Alexis Wajsbrot explores the challenges posed by creating the VFX shots for "Doctor Strange"...

As much as Dr. Stephen Strange learns to conjure multi-dimensional and magical powers from the Ancient One, he also needed assistance from Marvel Studios VFX Supervisor Stephane Ceretti, and an enclave of vendors that included the digital wizards at Framestore.

Creative Spark

Work on over 365 visual effects shots for Doctor Strange commenced on October 2015 and concluded September 2016 for Framestore CG Supervisor Alexis Wajsbrot. "The main weapon of Dr. Strange in the film is the Eldritch Whip and Rhune Shield, created completely by sparks and energy. Because they were made of sparks, it was easier to imagine and get the look right.” The digital sparks were created via a modified setup in Houdini that enabled more control of the length, curvature, and the location of the hot point, as well as allowing for the creation of a forked effect at the end of the spark.

"On-set they were already aware that Benedict Cumberbatch was going to be lit by these sparks, so for all of the whip shots he used a LED wire of lights which was really helpful in providing interactive lighting. When Dr. Strange is conjuring the whip or shield we had to closely body track the character and relight him. The lighting from millions of spark particles can be quite expensive and noisy in Arnold, so sometimes we were faking it with additional light. In a lot of shots the character and environment are full CG, so there was not much in the way of problems as we were controlling everything.”

Astral Projection

An out-of-body experience evolved from being a complicated visual effect into something simplified. "We did a lot of host of iterations to nail the final Astral Projection,” explains Alexis Wajsbrot. It was hard to find the right balance between making the effect interesting (not just a semi transparent character) and being subtle enough to favor the actor performance. There's not the same level of transparency everywhere on the character. It was trial and error from shot to shot. For instance, if you have a very blue background then the character is going to look very blue, so we compensated through grading. If there's a big red light in the background, you don't want it shining into Doctor Strange's face, so you have to blur the background through the character.”

"[Framestore VFX Supervisor] Jonathan Fawkner and Stephane Ceretti wanted to always rim light the character,” states Wajsbrot. "We made sure that around the body we always emitted the Astral Bleed Effect, which looks a bit like an aurora.” Framestore controlled the effect through compositing. "We had this whole fight between the Strong Zealot character and Doctor Strange in Astral Form in a hospital operating room, and during this sequence both of them are lighting the environment in different ways. Strange is wearing a blue costume and Strong has a reddish outfit. The environment was already lit but we still had to relight it. We had to model the whole operation room with an incredible amount of detail and props, and we had to track them on a ‘per element' basis. Strange and Strong are full CG most of the time during the Astral Fight because they are flying through the room.”

Mandelbrotting

A signature visual effect is the kaleidoscopic reconfiguration of buildings known as Mandelbrotting. "We had the arrival of Kaecilius and the Zealots who are Mandelbrotting the whole environment to open the doors and enter the Sanctum foyer,” states Alexis Wajsbrot. "After that, Strange is running away and Kaecilius is Mandelbrotting the corridor so it gets longer and longer so he does not move up at all."

"Then we have the Tumble Dryer Sequence where the whole corridor is rotating and Mandelbrotting. We had to model to a high level of detail, texture and look development for each scene. We did that for all of our environments. We began with animation to be able to choreograph what the set was doing. There were so many props that needed to be modeled and textured, and required look development. They built their own set which was then replicated in CG.”

"The set was so complex that we couldn't rig it,” reveals Alexis Wajsbrot. "I spoke to my rigger and asked him to create a controller on every piece of geometry. We ended up with a rig that took 24 hours to build because there were over 27,000 controllers and more was added to the set. Then we decided to give the animators the power to rig a set and move the pieces as they wanted without the need of a rigger. It was a big challenge for Framestore to fit that into our pipeline. We didn't want a massive geometry bake which would have been memory intensive, so we utilized our own proprietary tool FrInstancer, where you can take one piece and every similar piece is just instances of this one.”

Despite being distorted, buildings had to be identifiable. "That's why we started with animation and didn't go fully procedural because we needed to recognize the Sanctum even when it's moving in lots of different ways,” remarks Alexis Wajsbrot. "We started in Houdini to implement the Mandelbrot function. After Animation had done their part, we went into FX to use the Mandelbrot function to add a level of detail and magic. We used Houdini to do so where we had to convert the set into a volume, Mandelbrot it, and then at render time convert it back to a geometry; it was quite a challenge to keep the textures and look development during this process. We were also not happy with the level of detail we were getting using this technique. We decided to keep this workflow for FX to visualize the Mandelbrot and choreograph it , but implement a shader with the same Mandelbrot function that converted the geometry as an ISO surface and Mandelbrot it at render time.”

Digital Doubles

CG versions of Doctor Strange, Ancient One and the Zealots were created at a high resolution with complex cloth simulations. "The first step was how to model all of the cloth for the digital double,” states Alexis Wajsbrot. "Usually we model some wrinkles directly into our cloth. We wanted to do something smarter on Doctor Strange by using Marvelous Designer, which is a tool used in the fashion industry to model patterns like a true cloth designer. Marvelous Designer can simulate the cloth directly onto the character so it creates realistic wrinkles. Some of the cloths are incredibly complicated. The costume of Dr. Strange is made of 150 little pieces of pattern mixed together.”

"There were two different Cloaks of Levitation,” remarks Wajsbrot. "The normal cloak is the one worn on-set and it's a bit more static. The action cloak needs to be able to move fast.” The stitches of the cloak were groomed. "The cloak has been a true challenge to model and simulate because it's a character. How do you give it a personality? It was always about trying to find the right balance between being animated and dynamic. So we had to do a complex rig where animators could animate and place the cloak where it's supposed to be. They also had some simulation tools placed directly into the animation rig.” Cyber scans were not utilized for the cast. "We modeled the skin and the face based on some PhotoScans where we put an actor into a booth with 120 cameras, take all of the pictures at the same time, and we also had a scan.”

Rotunda of Windows

Six different environments needed to be produced for the Rotunda of Windows. "To the left is a pine forest, in the centre a CG ocean, and to the right the Andes,” states Alexis Wajsbrot when discussing the magic portal that opens up to different settings situated around the world. "But when Strange turns the dial, the middle window changes and leads to a desert and then a jungle and then switches it once more to the Grand Canyon. They look like proper CG environments because the camera is moving and you're suppose to see some parallax. In the jungle it's raining and there's a massive amount of wind so all of the trees are moving and reacting. We did probably 30 different versions of how the environments should transition from one to another. It's a quick effect in the movie. It takes a second to go from one environment to the other but the transition still needed to be designed.”

Mount Everest

"They built the top of Mount Everest on-set but there wasn't enough snow, so we recreated a CG version,” remarks Alexis Wajsbrot. "We had just finished work on the movie Everest so we had a lot of references from that and numerous effects to use as well. In this shot there's a special gateway because there's so much wind on Everest. The sparks are all flying around interacting with the snow, wind and mist. It was a quite intense sequence.”

Skyline & Space Porthole

"They shot a panorama of the New York environment,” states Alexis Wajsbrot. "It's more 2.5D so we modeled geometry for that. It was a lot of matte painting work to find the right time of day. For this environment we're in the Astral World and the Ancient One is slowing time. It's snowing during the sequence but the snow is very slow, imperceptibly moving. When they shot the scene there was some motion blur on the cards, so we had to remove that and paint back some lights in the city. There's CG snow and a CG helicopter flying slowly in the sky so you see the rotor spinning in slow-motion.”

Wajsbrot adds, "When Strange is in his Astral Form normal people like you and I can't see him so he has a way to make himself visible which is to go through this space porthole. The air is made of shards of glass but it's not really glass, otherwise it wouldn't be scary or would look too fragile. We spent a lot of time thinking about the design, because it couldn't look like anything real you've seen before. "

Crimson Bands of Cyttorak


"Strange and Kaecilius are fighting and the Cloak of Levitation is leading Strange towards the Crimson Bands of Cyttorak, which is a weird harness made of metal,” explains Alexis Wajsbrot. "Strange throws the Crimson Bands of Cyttorak which automatically locks Kaecilius in a weird pose. They shot Mads Mikkelsen on-set but we couldn't use it because the Crimson Bands of Cyttorak needed to interact with the cloth. It was probably the most complicated creative effect and cloth simulation that we had to do in the movie. We put a team of four of our best artists on it. We are all proud of this shot at Framestore.”

Related links

Doctor Strange on iMDb
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