Indeed, Wentworth adds that in making Piranha 3D, they had to navigate rough MPAA waters in steering clear of an NC-17 rating, especially with regard to a notorious penis shot, along with fixing and augmenting nudity.
In fact, Wentworth suggests that director Alexandre Aja (the upcoming Space Adventure Cobra and The Hills Have Eyes remake) always had something in mind along the lines of a horror version of Porky's.
"Alex had this idea of creating a cool 3-D horror film and thought it was something that hadn't been done before in a medium that's just starting to come into its own, so I was pretty excited about it and jumped on board," Wentworth explains. "It's the middle of spring break and an earthquake releases all these prehistoric piranha and they go on a feeding frenzy."
That noodling went back and forth between several vendors early on (including Intelligent Creatures ), before a change of direction necessitated the creation of an in-house vfx unit through the Weinstein Co. called Flat Earth, under the animation supervision of Don Waller. In all, there were around 325 shots in the final film, with most of the CG concentration on the fish and rock formations and the aforementioned nudity and gore.
"Don took the reins of the hero animation," continues Wentworth, "and a lot of the schooling animation was done at Gradient , and some of it was also done at CIS Vancouver . I think they both used Massive . Maya  was used for hero fish. Flat Earth used mental ray . Gradient and CIS are more RenderMan -based with 3Delight ."
Meanwhile, 3-D proved to be the biggest challenge. Initially, the director and supervisor wanted to make it in 3-D, but budget and shooting conditions proved too daunting. So it was predominantly converted by a new company called inner-D.
"It was a little bit cheaper to convert it and it gave Alex the ability to use film and go anamorphic and have that dynamic range you get with film. And that was important because a lot of what we were filming was on water and you have a lot of reflections and highlights that cause problems with a lot of the stereo rigs through polarization. So the decision was made to post convert it.
"We had a lot of problems early on. It's an incredibly complicated and time- consuming process. We weren't happy with the amount of depth we were getting in the images and some adjustments needed to be made by inner-D. But, I have to say, this is one of the best examples of the converted movie to date. Some shots look better than others and there are shots that can't be converted: they have to be done in visual effects.
"We took a few shots off the plate and gave to a visual effects vendor and vice versa. The ones with big negative parallax were done with vfx."
Wentworth definitely thinks the future of live-action 3-D will be a mixture of post conversion and full CG stereo delivery by vfx companies. "Generally speaking, it's about how much you want stuff to come out of the screen. With conversion, it will start to break after a certain point because you don't have the information you need between the left and the right eye for the audience to see one or the other side of an object. The worry is that you don't want these things to become too gimmicky. But this is stuff you [definitely] haven't seen before."
Bill Desowitz is senior editor of AWN & VFXWorld.