See example at Onepixelahead
points are created with 3 data fields x, y, and z. 3 or more sets of points are needed to create a face. Front face vs back face have traditional been determined by the order of the points — clockwise vs counter clockwise. The faces then need to be painted, do they face the light? Bitmap textures need to be transformed into a perspective view and be properly lighted. Shadows require dropping down to the pixel level — which is ray tracing not openGL at this point in time.
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.