Valve's continued silence on the Half-Life franchise has been frustrating for fans, desperately wanting to believe that anything could be part of a viral marketing campaign to announce a sequel. Nearly six years have gone by since the release of Half-Life 2: Episode Two, and it appears fans will have to continue waiting.
Writing on his blog (via Kotaku), Lowrie claims that "the biggest challenge with bringing out HL3" is motion capture. Valve apparently wants to capture performances, but have yet to clear the technical hurdle of being able to make mo-cap interactive. "Once you film the actor doing something and capture that motion, that's what the character is going to do," he said. As a result, "as far as I know they are not developing HL3 now for several reasons, among them the mo-cap issue."
The comments have since been deleted, but prior to their removal, he did note that Valve doesn't "tell me their business plans," and that he has "no idea what they're planning for the future." So take his claims with a grain of salt--extracted from the tears rolling down your face at HL3's continued absence.