Away3D is a realtime 3D engine for Flash in ActionScript 3.0. Started in 2007 by Alexander Zadorozhny and Rob Bateman. The engine is Open Source under the Apache 2.0 license and is free to use for any purpose, also commercial projects.
Import/export of several popular formats, including animated meshes
25+ useful primitives and a solid selection of material types that you can easily extend yourself (see below).
Several renderers offering varying degrees of complexity vs speed.
Solid Actionscript API that is now in the fourth iteration. Version 4.0 and upwards will support the Stage3D API (aka Molehill) taking the rendering from the CPU to the GPU. This will enable polycounts that are in the millions rather than the 4-8 thousand that are possible with the Flash Player 10 version of Away3D
Away3D is also the only Open Source 3D library for the Flash Player that is still actively maintained and keeps adding support for new features and new Flash Players
Materials / Shaders
Color, bitmap, phong, outline, flat, video, enviro, bump/ normal map, fresnel, glass, lambert, surface scattering, shadow / light maps and more.
Several Camera types such as free, target, hover, chase, Camera lenses (ranging from fisheye to isometric)
Point, ambient, directional
Standard primitives include Cube, Sphere, Cone, Cylinder, Torus, Billboard, Planes and many more. All the way down to LineSegments to Triangles, allowing you to construct any primitive yourself.
Rectangle, nearfield, frustrum
ASE, AWD, 3DS, MD2, Collada, MQO, KMZ and OBJ
AS3 class, AWD, Elevation2AS3 and OBJ
Align, AlignToPath, Explode, Grid, Merge, Mirror, Replicate, Weld
Lathe, Path, Segments, Elevation
Utilities / debug
FaceLink, Trident, Normals display
Prebaking of lights to textures, NormalMap generator, BSP generator
3D audio, Vector sprites, 3D Text
Prefab3D companion app
Written in Adobe AIR, this companion app provides a visual interface to many of the most advanced Away3D features such as the generators, but also adds a bunch of tricks to your arsenal such as visual tweaking of UV maps, path editing, optimization and error checking of imported models, export to several formats (including AC3D) and it even has a a live connection to your Flash file, so you can export and play with geometry created at runtime.
Rendering of prebaked textures on a BSP model using Prefab3D
AwayPhysics is an extremely fast Alchemy port of the widely known Bullet Physics Engine. It is specifically designed for Away3D 4.x, providing an optimized, closely coupled physics library to Away3D users. 3D physics in Flash have never been as fast!
… and much, much more.