Adobe also has a tool called Pixelbender 3D where you can write shaders in their flavor of HLSL. Its an extension to pixel bender (which was for 2D shaders only). Pixelbender 3D has to be used offline though, so if you want to embed shaders in a swf they have to be written in assembly. The reasoning for this is that the pixelbender shader compiler is larger than any single part of the flash runtime, so it would greatly bloat the flash runtime for a little bit of developer convenience. Adobe has done a poor job of showing that you can use high level shader code in their demos though, pixelbender will end up being the preferred way to author shaders for molehill, the assembly stuff will only be used by a few people for tests\quick hacks.