Flash Player 10 & Flex Builder: Class flash.geom::PerspectiveProjection could not be found.

I got this runtime error when trying out the new 3D features in the latest Flex SDK:

VerifyError: Error #1014: Class flash.geom::PerspectiveProjection could not be found.

This can be fixed this by setting the Flash Player version to 10.0.0 (or whatever fp10 version you’re using) in Properties > ActionScript Compiler > HTML Wrapper > Require Flash Player Version. This version number not only for the HTML wrapper, but also for the flash player SWC include file.

If you have problems compiling the project and/or your code completion doesn’t work, you need to make sure you have the flash player 10 swc file in your build path. It can be found in the SDK under frameworks/libs/player/10.