In order for Gnome3 to properly work with 3D acceleration, the gdm user should be added to either the wheel or video group. The handbook doesn't mention this but I think it should in section 5.7.1.
This seems to affect more than gnome/gdm users.
I installed xfce4 on FreeBSD 11-CURRENT and discovered that adding myself to the video group enables 3D acceleration. There's quite a big difference in desktop responsiveness. Using YouTube is much faster.
(In reply to Yonas Yanfa from comment #1)
Making the X user a member of the video group is documented already, in both the Quick Start and the first section after it:
This bug is specifically about Gnome. I don't know the requirements there.
(In reply to Warren Block from comment #2)
> Access to /dev/dri is needed to allow 3D acceleration on video cards. It is usually simplest to add the user who will be running X to either the video or wheel group. Here, pw(8) is used to add user slurms to the video group, or to the wheel group if there is no video group:
I was part of the wheel group, but I needed to be part of the video group. The documentation needs to be updated, but we should create another bug report for it.