While no major studio tentpole has bumped a release date due to visual effects delays since “Titanic,” Warner’s efforts at 3D conversion provide a glimpse of the kind of problems a studio could face if it pushed the vfx pipeline beyond the breaking point.On “Clash of the Titans,” Warner decided late to convert the movie to 3D, and moved the release date to gain extra time for its 3D conversion. But the 3D digital cinema packages that went to theaters were uneven, and the studio was bashed for it. Studio then had to give up on its planned 3D conversion of “Harry Potter and the Deathly Hallows — Part 1″ rather than miss the pic’s release date. Both pics ran out of time at the end of the process. “Compressed post schedules are a huge problem,” said Marvel’s exec VP of visual effects, Victoria Alonso. “The amount of changes we rely on doing in post are hardly reflected in the schedules. Part of it is that no movie has failed to deliver yet, but the comment I hear on a consistent basis is ‘Picture X’ did it in half the time we have, how come we can’t do it in double the time?’ I don’t like that comment because no movie is ever the same.” The industry’s shift to 3D for vfx-heavy pics has made already-tight schedules worse. Native stereoscopic vfx are more difficult to create and every frame has to be rendered twice, from slightly different viewpoints. That eats up limited computer time and resources. Converting vfx shots to 3D requires weeks after the 2D version is complete. For example, Alsonso said Marvel sent “Thor” vfx to Stereo D for conversion in October 2010 for a May 2011 release date just to avoid a crunch at the end. “Green Lantern” is using both native and converted 3D, and had to allow time in its schedule for conversion.