In painting characters in a fresh way, the artists, it seems, had also rendered the would-be critics docile.

Ever since 20th Century Fox and Blue Sky Studios helped announce a CGI “Peanuts” feature film due in 2015, legions of followers had begun fretting: Would a digitally rendered Linus and Lucy and Woodstock lose all the artful charm that characterizes the beloved strip and specials? The worst-case CGI scenarios spooked fans’ imaginations, as if haunted by a hologrammic Garfield voiced by Bill Murray (a filmic flashback that puts the Odie in “odious”).

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The “Peanuts” animators had put long months into trying to stay true to the spirit and style of creator Charles Schulz. But in March, a quick litmus test was shared with the world — most notably, with the millions of protective die-hards in Charlie’s armies.

So, does this two-minute-plus trailer featuring Snoopy and Charlie Brown mark the first successful step in a core visual mission: To somehow blend the cool-eyed realism of CGI with the line-drawn warmth of the master’s hand?

Yes, Hollywood.

The Beagle has landed.

But how did the filmmakers get to this point — and with the big launch date just a year and a half away, where do they go from here?

2. The Seed

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It was 2006 when Craig Schulz sat down with the seed of an idea.

Six years after his father’s death, the popularity of “Peanuts” was holding ever strong. The feature’s characters were so ingrained in the culture — like icons embedded in the national psyche — that most client newspapers were continuing to carry the strip, and the merchandise kept selling, and phrases coined by the cartoonist continued to be part of the everyday vernacular. And, quite significantly, the animated specials continued to garner high ratings.

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Amid this lasting appeal, the cartoonist’s son had a short-format concept for a “Peanuts” film. And once he had the idea down, he turned to the third generation. “I was happy to show my son,” Craig says of Bryan Schulz, a screenwriter. “He showed me how to make it bigger — how to blow it up more — and he helped me put in structure.”

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Craig Schulz, though, proceeded with caution. 2015 will mark the 65th anniversary of the launch of “Peanuts” by United Feature Syndicate, and it is dicey to tamper with the legacy of, and love for, Charles “Sparky” Schulz’s institution of a creation.

“Nobody is more protective of the comic strip than myself,” Craig Schulz tells The Post’s Comic Riffs of his father’s brainchild. “The only one who would be more protective is Jeannie” Schulz, widow of the “Peanuts” creator.

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That was foremost in Craig Schulz’s mind as his seed of an idea began to bear fruit. “The time was right,” he says, “and we worked out a story, and we brainstormed.”

The “Peanuts” brain trust met with different Hollywood teams, laying the terms on the table. “If we’re going to do this project, it has to be under Schulz control — this is a Schulz film,” Craig says. “No one is going to grab and run with it. We need to have absolute quality control and keep it under Dad’s legacy. … You can’t bring people in from the outside and expect them to understand ‘Peanuts.’ ”

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So the dance continued to find the right Hollywood partner — someone who would take the time to understand “Peanuts.” The Schulz family met with Fox and Blue Sky, and the union clicked. “Vanessa Morrison and Ralph Millero stood behind us,” Schulz says of the president and vice president of Fox Animation.

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“We are proud to work with the Schulz family and [corporate] Peanuts Worldwide on this film … ,” Millero tells The Post. “I have always loved comic strips, especially Charles Schulz’s ‘Peanuts.’ ”

Now, the film project needed perhaps its most crucial hire — someone to climb wisely into the director’s chair.

3. The Hire

“We’ve all been Charlie Brown at one point in our lives.”

Those are the words of Steve Martino –an Emmy-winning writer-director with Blue Sky who has worked on the studio’s “Ice Age” franchise. And that is the connection to character that Martino carried into his meeting with the keepers of the “Peanuts” flame.

“We met with him and discussed what he’d done in the past,” Craig Schulz recounts. On the filmmaker’s resume, they hit a touchstone: 2008’s well-received “Horton Hears a Who!” To land that animated film, co-director Martino had gone to meet with the family of another American artistic genius of the past century who had also died in more recent years — and whose legacy, which included classic animated holiday specials, was being closely guarded by the kin.

“He met the Geisels and talked to Audrey,” Schulz says of Martino’s trip to La Jolla, Calif., where he shared his creative vision with Theodor “Dr. Seuss” Geisel’s widow. Audrey Geisel, in turn, shared her husband’s world with Martino.

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“She personally walked him through a lot of stuff in the house,” including closets that contained her collections of things, Schulz says. “And she told [Martino] what she expected of him” with the movie.

Given that success, Schulz says Team Peanuts felt confident it could expect the same sense of vision from Martino on its film.

“Like with Ted Geisel, my passion comes from my love for the art he created … ,” Martino tells Comic Riffs. “You start with the love of their work and then really study what they’ve done.”

“You get as close to the person who created the work as you can,” the director says. “I want to do it through that spirit.”

4. The Trip

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For many filmmakers, inspiration begins with a field trip.

In Martino’s case, Blue Sky Studios is in Greenwich, Conn., while the Peanuts base of operations is in Northern California. As with his Dr. Seuss film, Martino’s most logical step was to visit the creative epicenter of “Peanuts.” The director wanted to walk the grounds, and see the sights, where Charles Schulz drew daily inspiration.

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“I got to go to Santa Rosa to go to a Peanuts exhibit,” Martino says. “I saw where his drawing table was set up. And I saw a video of him drawing those characters. I watched how he lays the ink down. …

“I needed to become more of an expert in the details.”

The cross-country creative process was ramped up. Blue Sky crew members visited Santa Rosa. A group of storyboard artists headed west.

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“I have been delighted that Steve Martino and his Blue Sky animation team have chosen to make Sparky’s studio here in Santa Rosa sort of a second home,” Jeannie Schulz tells Comic Riffs. “Here, they can absorb what still has the feel of Sparky’s presence, as well as visiting the museum to look at original art.

“I know Steve’s primary goal in the movie is to be true to the feel of the comic strip and the previous animation.”

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“It’s been fantastic to work with Craig Schulz and [co-screenwriters] Bryan Schulz and Cornelius Uliano, and Jeannie Schulz at the museum,” Martino says. “It’s like taking [courses] at Peanuts University.” (The film is being produced by the father-son Schulzes and Uliano, as well as Michael J. Travers and the Emmy-winning writer-director Paul Feig [“The Office," “Freaks and Geeks"].)

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The Blue Sky crew met with Team Peanuts illustrators like Paige Braddock (“Jane’s World”), who Martino says is “a phenomenal artist in her own right.” And by studying video of Sparky in Santa Rosa, Martino says his team tried to dissect: “How does he make that line?”

“We want to track down the idiosyncrasies of the hand-drawn feeling,” Martino says of his team, which includes such Blue Sky veterans as cinematographer Renato Falcao and art director Nash Dunnigan. “We want to bring the magic of his pen into this [CGI] world.”

Charles and Charlie: The creator and his star, rendered with a magical line. (Peanuts Worldwide)

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5. The Canvas

When hand-drawn warmth gets adapted into the cool pixel-precision of CGI, the fear is often that something will get lost in the translation.

Steve Martino knows he is trying to bridge this chasm between two distinct visual languages. As the director also knows intimately as an artist, there are inherent obstacles to crossing that technological gap.

“I’ve talked to Craig a great deal about this,” Martino tells us. “His dad understood that when he drew for comic strips, he drew for one canvas. And he was very aware that for animation, you paint on a different canvas. There’s a different way for it to work.”

For Martino’s crew, that first meant acknowledging that trying to replicate a hand-drawn work is not a particular strength of the CG medium. “I told my team of animators to embrace that limitation and turn it into a style. They embraced that challenge.”

For clues to unlock these visual mysteries, Martino kept returning to the source material. “My mantra to the team was: ‘Find the pen line of Sparky — the way he shaped Charlie’s head.’ ”

For example, “Where there’s a worried line [near] the eyes, it’s never symmetrical,” the director says. “With [CG] characters, you want to make everything more symmetrical. My job is to beat that out of it — to find how to put that asymmetry back in. …

“We spent well over a year studying how [Sparky] put pencil lines down and how he created that emotion — how the dot of an eye [conveyed] joy or sorrow” so efficiently.

“Really, it’s a Picasso drawing,” Martino says of Sparky’s visual genius.

“There was an early learning curve for the first year,” Craig Schulz says. “One thing we struggled with: How to make Charlie Brown move.”

In trying to create a style of movement for the characters, though, the filmmakers needed to solve a range of visual challenges. Fortunately, an animation master had already traveled along this path.

6. The Master

The Blue Sky artists hit obstacles as they tried to create each smooth-moving figure. Some of them were fresh off the animated film “Epic,” which, as Craig Schulz says, is “as close to human movement as you can get” in cartoon form. And they also wanted to make sure they were rendering feelings and emotions and facial expressions that audiences could relate to.

They had studied Charles Schulz’s line. Now they needed to study the work of a man who had been in their shoes.

“We step off of a legacy of how Bill Melendez created,” Martino says of the late Emmy-winning animator. “I go back to the Christmas special,” 1965’s “A Charlie Brown Christmas.”

When Melendez visually adapted the static comic strip for the screen, he had to “paint on a different canvas,” Martino says. “There’s a different way for it to work. … Our animation harks back to what Melendez had done. His style drew off of what Sparky drew.”

For example, Martino explains, “Sparky drew Snoopy on the doghouse, the Flying Ace … but Bill Melendez [had to] make him fly — he put him up in the air. That’s amazing. …

“We hopefully can take another step and take Snoopy into some action [in 3D animation] in that same kind of progression as Melendez did with 2D animation. … Now we’re painting on a bigger canvas.”

The filmmakers also want the spirit of Melendez to grace the film more overtly. “I really wanted Bill Melendez” to voice our Snoopy, too, Martino says.

“We dug into the archives of Bill doing Snoopy and Woodstock and we got the rights to use that,” Schulz says. “And we met with [producer] Lee Mendelson and got the rights to the music.”

“Listening to the clips of him laughing as Snoopy — that is liquid gold. It’s so infectious,” Martino says of the Melendez archives. “I’ve heard it over and over, and I can’t help but laugh. It’s great to be able to use his voice.”

That, however, is the only voice actor “Peanuts” filmmakers will divulge. “In terms of casting, we haven’t announced our cast,” says Martino, who previously has worked with the voices of Jim Carrey, Amy Poehler, Steve Carell and Carol Burnett. But, it will “follow the same thing that was done on the first Christmas special, [with] the charm of kids’ voices. With Linus saying something philosophical and very adult coming out of a voice of someone so young.”

[‘A CHARLIE BROWN CHRISTMAS’: Producer illuminates the holiday special’s enduring appeal]

Martino is also tight-lipped about what the film’s narrative will be, though he will tell us: “Here’s where I lean thematically. I want to go through this journey. … Charlie Brown is that guy who, in the face of repeated failure, picks himself back up and tries again. That’s no small task. I have kids who aspire to be something big and great. … a star football player or on Broadway. I think what Charlie Brown is — what I hope to show in this film — is the everyday qualities of perseverance…to pick yourself back up with a positive attitude — that’s every bit as heroic … as having a star on the Walk of Fame or being a star on Broadway. That’s the [story’s] core.”

“This is a feature film story that has a strong dramatic drive, and takes its core ideas from the strip.”

7. The trailer and beyond

As March approached, so, too, did the deadline for the film’s debut trailer. Was the animation ready for its close-up?

Would those fussbudget fans and anxious critics, in other words, appreciate how Blue Sky was, as Martino says, “bringing these characters into a beautiful CGI world”? How would viewers react to blending the coolly precise pixel and the warm, hand-drawn liquid line that almost appears to sit atop the CG realism like an overlay?

“My hope is that we’re lifting a filter,” Martino says. “Charlie Brown’s shirt has a cotton texture, and shoes made of leather. We walk into this world and see the shapes and objects and [know they’re] completely derived from what Charles Schulz drew.”

“I was with my family members, and it brought tears to their eyes when they saw the trailer,” Craig Schulz says. “There was the fur on Snoopy, and you could feel the texture and the way the clothing moved.”

Now that “Peanuts” fans have embraced the trailer, the filmmakers know they’ve got to continue with this high-level commitment.

Martino likens the creative process to a roller-coaster ride. They’ve scaled the incline. “Now we’re at the top of the hill,” he says — and ready for the acceleration.