If one goes back a ways one will find DirectX
This object API was limited to windows systems which have installed the object. Gave limited support for a 3d image. .x file format. The file format and the API gave little support for animation. Apart from rotations.
OpenGL is different it is supported by a wide range of systems and required for certain games to operate on the system. In fact Daz 3d studio fast mode animates in OpenGL.
I still have questions as to what and how access will be provided through the browser. If textured animated objects can be created on the users system and XML data which only contains the location and rotation of objects which have an imaginary skeleton to move objects attached to other objects. In other words a manageable amount of data to transmit to other systems in real time. Then what we have now for flash games are going to look like a ten year old arcade games very quickly.