The ‘floating cube’ tower for S.F. looks great — but don’t believe what you see

Architectural renderings aim to deceive. They only show what the creator wants to show, from the chosen angle at the chosen time of day, and blur any messy details that might break the desired mood.

So when a developer files a proposal for a 62-story tower far out of kilter with its surroundings, and adorns the filing with a bare two images that depict the extruded shaft as if it were a mystical matchstick — I’m sorry, “a subtle glowing lantern” — you should take this supposed glimpse of the future with a skyline-scale grain of salt.

This tower would be 640 feet tall and hold 826 apartments, according to the proposal filed last week with San Francisco’s planning department. Of these, 15% would be reserved for very-low-income households, which translates to an income of $49,900 for three people in an apartment.

But enough of, you know, actual details. What made the rounds on the internet last week after the 49-page application was submitted was the pair of sexy/heroic renderings of an extremely elongated grid, square windows and a square floor plan, topped by five stories clad in white that seem to hover in air.

That’s because the tip of the match would be visually separated from the rest of the tower by a 29-foot-high “amenity floor” clad in glass and pulled back a foot or two from the cladding above and below.

“The slender tower achieves pure articulation... (and) contributes meaningfully to its shared skyline,” the four paragraphs of text assure us, conjuring up gauzy visions of the newcomer “hovering above SOMA like a subtle glowing lantern... both unique and expressive of its time, but also complementary to its historic Bay context.”

Sounds downright seductive. But if you also want glimpses of the high rise within the actual city, the proposal turns a lot more coy.

The design is by Arquitectonica, a Miami-based firm with a mixed track record in San Francisco, even though its renderings always have an energized glow. The developer is Align.

We get no view of how the tower would meet the street, just diagrams showing that the developer wants to go straight up, up, up. Align also wants separate curb cuts for a subterranean parking garage and a loading dock, which would consume nearly one-third of the ground floor along the sidewalk.

As for the materiality of our hovering homes and the dark rod below... your guess is as good as mine. The project description assures us of “high-quality materials with transparent and framed structural elements.”

And the hovering cube?

One rendering with the tower glowing against a clouded dusk sky accents the “subtle glowing lantern” with a see-through amenity floor except for the central core holding the elevators and stairs. As in, lacking any interior walls like the ones shown on the floor plan a few pages away.

The other rendering takes us even further into the realm of make-believe — in the morning light our lantern floats untethered, without even that structural core.

“In the rendering it looks pretty neat,” Rich Hillis, the city’s planning director, is happy to concede. “I’m not sure how you actually build it, though.”

Don’t look for edification from the developers, either. I reached out on Monday to their local partner and was politely told that they’re declining to talk about the proposal.

One reason for the silence might be that Align has the upper hand in terms of getting the project approved: State law allows developers to increase the square footage of a project by 50% if 15% of the units are reserved for households making no more than 50% of the region’s median income.

Known as a density bonus, this is a laudable incentive in many ways — but San Francisco’s affordable housing requirements generally already are at this level, so developers who drop the rents for a unit or two hit the jackpot.

Basically, they get a bonus for something that San Francisco requires them to do. And the city’s ability to vet design aspects of the project get constrained, as well.

“It’s hard to argue against the policy goals of the state,” Hillis said. “There is an affordability crisis in California, and a housing crisis.”

The zoning for the 620 Folsom site has a 320-foot height limit that dates back decades; given San Francisco’s housing needs (and the history of local politicians self-righteously downplaying the need), there’s a case to be made for rethinking locations that in the past received little notice.

But treating the city’s zoning map as a gameboard to be exploited for loopholes, and then using gimmicky designs to get some online buzz, treats the real city down on the ground as an afterthought. And in the long run, that could corrode the physical qualities that have helped San Francisco endure as a compelling place to be.

John King is The San Francisco Chronicle’s urban design critic. Email: jking@sfchronicle.com Twitter: @johnkingsfchron