Almost two years after the crippling defeat of a proposal to build a football stadium in Manhattan, the city and state unveiled sweeping new plans to remake a giant parcel of the West Side’s Hudson Yards last night.

Speaking at a public forum in Midtown, officials detailed plans for a 26-acre complex of residential and commercial towers, set amid expanses of open space, to be built atop the Hudson Rail Yards, three blocks east of Pennsylvania Station.

The guidelines for developers, the city and state officials said, would include provisions for up to 20% of the rental housing within the complex to be “affordable,” an amount many attendees were quick to dub inadequate.

A large crowd turned out in support of preserving the High Line elevated rail bed on the western half of the site and transforming it into parkland. The state had previously indicated that including the High Line could decrease the value of the site, but an official from the Metropolitan Transportation Authority, which owns the rail yards, spoke positively of the High Line, though he did not make a commitment to preserving it.

“What the MTA has to do is understand the risk and reward,” the director of special project development and planning at the MTA, William Wheeler, said.

The MTA aims to put the project out to bid by the end of the month, and people familiar with the plans for the site say five large developers are currently working on proposals. Once a developer is selected, the project would need to go through the city’s public review process, which requires approval from the City Council.