I'm trying to change the rendering from OpenGL to Direct3D, yet there's no option in the config.ctf file as older forum posts on the issue indicate.  Older forum posts also talk about an additional options menu at the login screen where there's the option to change the rendering method, and this was confirmed by a current player in-game.

Problem is, where's my options menu?   The login screen consists of little else than my login name, password, a connect button, options for creating and editing an account, password recovery, and an option to place a support ticket.  At the very bottom of the screen are options to change resolution and preset levels of detail "Just a list like low, medium, high, custom" and an "exit" button but no configuration menu.

In the ryzom folder, there is an application called: ryzom_configuration_rd.exe to configure the game outside the game client.

Alternatively you can add or change the file client.cfg with the line:

Driver3D             = "Direct3D";

to use DirectX.

If the line is not present, just add it.

PS: Never change the file client_default.cfg!

Edit: you are right, now the client login screen no more contains the button to execute ryzom_configuration_rd.exe.