Here’s what the shadow from the Winthrop Square tower could look like

The first simulations to show the shadows cast by the proposed 750-foot tower (left) for Winthrop Square in downtown Boston were released by the developer this week. Developer Millennium Partners created separate videos for its shadow study, one (above) to show the effects only on the Public Garden (arrow A), the second (below, arrow B) only on Boston Common. In each example, based on different months, the shadow does not cross Charles Street, and Millennium has not yet released images that would show the shadow across both parks at the same time.

There’s been a lot said lately about the shadows that a massive skyscraper planned for Winthrop Square would cast on Boston Common and the Public Garden.

Its developers are hoping that some pictures will be worth more than words.

Millennium Partners has released animations showing precisely where — and for how long — its proposed 750-foot tower would cast shade on the two historic parks, which are protected by state laws that ban shadows from new buildings in most of downtown Boston.

The animations are a visual aid, designed to ease concerns that the tower would darken two of Boston’s most cherished public spaces during some morning hours. Mayor Martin J. Walsh needs the state Legislature to amend the shadow laws to allow the tower and trigger a $153 million payment from Millennium for the purchase of the city-owned site.

But the city has faced pushback from neighborhood groups and some elected officials who are worried that changing the law would open the door to more high-rises looming over the parks.

Two time-lapse videos prepared by Millennium were made public by city regulators this week. They are based on a preliminary design, and the developer cautioned it may still change the height or shape of the tower, which would alter the shadows as well.

One video isolates the shadow’s effects on the Public Garden, the other on the Common, and they show different days when Millennium estimates the impact will be biggest on each park.

They also illustrate how existing buildings already drape the parks in shadow in the mornings, on the Common in particular. And they highlight how quickly the shadows can change.

For example, the simulation for the Public Garden shows that at 7:01 a.m. on Aug. 24, a finger of shadow would reach fully across the park to Arlington Street. Twenty-four minutes later, that shadow has receded from the Public Garden.

For the Common, Millennium chose a day in September, when the shadow swings across the park for more than an hour in the morning, then disappears as the sun moves west.

The simulation does not show how the shadow falls on both parks at once, nor does it show any new shadow that falls outside the parks, cutting off at Arlington Street east of the Commonwealth Avenue Mall, though neighbors who’ve seen other images from Millennium say shadow appears to fall there, too.

Joe Larkin, who is in charge of the project for Millennium, declined to comment, citing the project’s ongoing public review process.

The second image shows shadows only on Boston Common.

But Jon Greeley, director of development review for the Boston Planning & Development Agency, said the simulations were a smart way to illustrate the effects of the tower.

“It’s all kind of ethereal until you’re seeing the animation,” he said. “Then you see the shadow’s not static. It’s moving. It’s not just laying there on the Common for an hour and a half.”

Greeley acknowledged the videos were incomplete, and said the BPDA would like to see a version that shows the effects on both parks at the same time. The city’s review process also requires Millennium to perform a more-detailed shadow study.

But since shadows will play a big role in debate over Winthrop Square, Greeley said, it’s helpful to have more information up front.

“We’re going to have a much fuller examination of all this,” he said. “But this is a great start to helping people understand how shadow works.”

It helped Ben Starr, who lives on Beacon Street and is a member of committee the city appointed to review the Winthrop Squae project. He saw the animation at a recent meeting and said it helped him visualize what had been an abstract effect.

“It was eye-opening,” he said. “It allowed me to better understand the exact impact, without having to just imagine it in my head.”