The 3D crunch heats up this weekend at the domestic B.O. as Paramount and DreamWorks Animation unleashes 3D toon “How to Train Your Dragon” at 4,055 playdates, occupying 2,150 3D-equipped locations with 185 3D domestic Imax locations added to the mix.

MGM’s R-rated comedy “Hot Tub Time Machine,” the frame’s only wide 2D release, debuts at 2,754 engagements.

With multiple 3D titles now in the market, and still more to come, studios are having to compromise as they face limited 3D runs.

Disney’s “Alice in Wonderland” enters its fourth frame at approximately 640 fewer 3D locations for a total of 1,450. That number is expected to drop even more on April 2 when Warner Bros. launches 3D pic “Clash of the Titans.”

At the specialty B.O., Sony Pictures Classics rolls out Atom Egoyan’s “Chloe” at 306 locations. Julianne Moore toplines in the thriller as a woman, who after suspecting her husband of infidelity, hires a young escort (Amanda Seyfried) to seduce him.

Focus Features will expand its Ben Stiller-starrer “Greenberg” to 181 locations in its soph sesh. The film launched last weekend at three engagements in New York and L.A., with $118,152 for a per-screen average of $39,384.

With 3D offerings added to a crop of strong holdovers, the frame could see another sizeable boost.

Last weekend’s performance was up 21% over the same frame last year, while first-quarter box office has seen a strong 11.9% uptick, compared to 2009.

Despite a recent increase in 3D ticket prices, “Dragon” should expect to see a major lift from the film’s 3D component. Some circuits are raising 3D ticket prices by more than 8%, while Imax tickets are being raised even higher.

The large-screen exhib committed to a six-week run of “Dragon,” opting not to screen “Clash” when it bows next week. Imax just finished its three-week run of “Alice.”

“Dragon” has received positive early reviews, with an aggressive marketing push. Par showcased sports-themed TV spots during the Winter Olympics, nearly a month before the film’s launch.

Set in a mythical world where Vikings and dragons co-exist, the PG-rated tale should be tops among tykes, but could appeal more to boys than girls.

Par said tracking for “Dragon” is consistent with family films, but “Alice” could still provide stiff competish.

Entering its fourth frame, “Alice” has cumed $273.3 million domestically as of Wednesday, and will screen at a total 3,384 locations this weekend. Pic has already become the highest-grossing March release ever, besting Warner Bros.’ “300,” which earned $210.6 million in 2007.

“Hot Tub,” starring John Cusack and Rob Corddry as part of a group of middle-aged guys who travel back to 1986, could gain traction among males 25 and under. Pic marks MGM’s first release since its musical remake “Fame,” which grossed a disappointing $22.5 million.

Studio mounted a viral campaign for “Hot Tub” on social networking sites. According to the studio, the film ranked No. 6 on Wednesday among Twitter users, with more than 30 million followers.

Among the frame’s holdovers, 20th Century Fox’s “Diary of a Wimpy Kid” opened to strong results last weekend, earning $22.1 million at 3,077 engagements. “Diary” scored a narrow victory over Sony’s wide opener “The Bounty Hunter,” starring Jennifer Aniston and Gerard Butler. Romcom landed in the No. 3 spot with $20.7 million, behind “Diary” and “Alice.”

Disney will debut its inhouse docu “Waking Sleeping Beauty,” about the Mouse House’s transition in the early 1990s, at five locations.

Magnolia’s “The Eclipse,” starring Ciaran Hinds and Aidan Quinn, also launches in limited release. Pic, which tells the story of a widower who develops a relationship with a horror novelist in a seaside Irish town, screened at the Tribeca Film Fest last year.

On the international front, Par will expand “Dragon” in some 30 territories, including Australia, Germany, Italy and Spain, having already grossed $7.9 million on 771 screens last weekend.

Toon bowed early in three markets, led by Russia, where it grossed $7.5 million on 600 screens. “Alice” dropped 72% in that territory, with $2.7 million on 576.

Overseas cume for “Alice” stands at $300.4 million. In its third frame, the 3D fantasy grossed $48.4 million at 6,687 screens in 49 territories.

“Alice” will expand to France and China this weekend. In China, the film stands to profit from a bevy of 3D screens, ranking second behind the U.S. in total 3D-equipped screens.