Four taxidermied dog heads of different breeds stare grimly out from their wall.

They're dead pets. Lovingly preserved by a family in Alfonso Cuaron's Roma, a black-and-white foreign language film following the hardships of a young maid in early 1970s Mexico City. If you look closely, those dog heads are impeccably detailed.

That scene, little does it show, was augmented by visual effects.

When we think of visual effects in movies, we tend to focus on what's obvious: dinosaurs in Jurassic Park, the Incredible Hulk, Dementors in Harry Potter.

We don't necessarily think of taxidermied dog heads.  

"Alfonso felt they were lacking some realism... that they didn't feel like actual dead dogs, so we replaced and augmented them with real dog elements," Aaron Weintraub, one of the VFX supervisors on the film, said via email.

That's right. Even Roma, an art house, period piece, is filled with VFX. That includes anything from digital set extensions and environments to human performances and, potentially, dead dogs.

Welcome to the world of "invisible effects."

Roma won three Oscars this year, including Best Director for Cuaron. It's a coup for distributor Netflix, after the streamer was banned from competing for the top prize at the prestigious Cannes Film Festival. Often Roma looks like a painting. It makes sense: one of Cuaron's Oscars was for Best Cinematography.

A wide, moving shot of a traffic scene features an old streetcar, lamps, buildings, flashing signs, billboards and storefronts. It's one of the biggest VFX shots of the film.

"To us, 'invisible effects' are effects where the audience never thinks for a moment that any extra work in post production was involved to achieve the shot and that everything was built practically and photographed with the camera on a traditional set," Weintraub said.

Invisible effects may not conjure up the spectacle of alien creatures, impossible-to-stage action and environments impractical to build, but they're an indispensable tool that productions will use to solve all manner of problems.

Behind it all is award-winning Toronto-based visual effects company Mr. X. Led by Weintraub, the team worked alongside sister company MPC in London to bring Cuaron's semi-autobiographical vision to life.

Roma washed onto Netflix's shore in 2018 and saw a limited release in American and Mexican theaters. For a year before that, Mr. X sent material back and forth with MPC for feedback in the shots they worked on to Alfonso's exacting specifications. MPC would review the shot material with Cuaron, then relay his notes back for Mr.X's artists to fold into their work.

The content of Cuaron's film itself struck a chord with Mr. X's team, some of whom hail from Mexico. "Although generally younger than Alfonso, [they] did connect personally with some of the material and helped guide the rest of the team through some of the geography and details," Weintraub said.

This scene is filled with VFX.

In Roma, main protagonist Cleo goes to the cinema with her boyfriend in a scene that proves heart-wrenchingly life-changing. To build atmosphere, as well as physical elements of the cinema itself, Mr. X replaced the cinema's entire stage with a full-size screen, added CG curtains that warbled the image as it projected over the characters, and illuminated the projection beam in the air so it bounced light back into the environment.

The before-and-after shots of that scene are detailed in a YouTube video Mr. X released on its channel. For an even more in-depth walkthrough of the visual effects used in Roma, see the below gallery.

Working with an auteur like Cuaron, whose 2013 film Gravity lifted the game for visual effects in terms of lighting, motion control and previsualization, shows just how far Weintraub has come. A fan of video games as a kid in the '80s, he gravitated to 3D modelling and animation and eventually found art and filmmaking through courses in high school.

Fusing those interests, Weintraub got his lucky break when he toured a local commercial animation company ("I lobbied my 10th-grade math teacher to organize a field trip") and it offered him a summer job. Staying on with the company while studying film and computer science at university, Weintraub eventually scored a position full-time. The company expanded and created Mr. X to work exclusively on film and television and the rest is history.

Weintraub crushed it on Shazam.

Weintraub and Mr. X aren't exclusively in the game of invisible VFX either. They recently finished up on Shazam, DC's latest (and most colorful) superhero film which is currently in theaters. "Shazam was an amazing experience," Weintraub said.

The shoot involved otherworldly creatures, 3D environments, matte paintings, FX simulations and digital doubles. For a design reference of how one character meets their demise, Weintraub and his team spent an afternoon on the roof of their studio shooting a timelapse of bacon frying.

"It was one of those projects where you get to flex all your VFX muscles," Weintraub said.

Weintraub and Mr. X have also worked extensively with Guillermo del Toro, the other treasured Mexican director. Those projects include gothic romance Crimson Peak, Oscar-winning fantasy The Shape of Water and vampire TV series The Strain.

"We have a great relationship with him," Weintraub said. It shows -- Mr. X's current projects are produced by del Toro, including horror film Scary Stories to Tell in the Dark and supernatural horror Antlers.

Less horrifying is del Toro and Cuaron's work ethic. "Guillermo, like Alfonso, is driven, exacting, relentless, and in full control of his specific vision," Weintraub said.

"Like all great filmmakers, he brings out the best in his collaborators."

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