Please, I need help with this. I've searched the 'net up and down, and, actually, I found several fixes. I tried them all, none worked.
Symptom :
I go to System settings -> Desktop effects -> Advanced.
In Compositing type, I set it to OpenGL.
I click Apply. It asks for confirmation. I confirm, and it says "One desktop effect could not be loaded."
I click Details in that error message. It says "Blur effect requires OpenGL".
Then it proceeds to obviously forget that I ever set it to OpenGL.
Then, I found an error in /var/log/Xorg.0.log. It says that
[ 816.691] (EE) AIGLX error: vboxvideo does not export required DRI extension
[ 816.692] (EE) AIGLX: reverting to software rendering
[ 816.696] (II) AIGLX: Loaded and initialized swrast
[ 816.696] (II) GLX: Initialized DRISWRAST GL provider for screen 0
[ 816.697] (II) VBoxVideo(0): Setting screen physical size to 444 x 277
(I tried to attach the whole file, but the board told me its attachment quota has been reached.)
Setup :
VirtualBox guest additions are installed.
The kernel module is loaded.
The xorg driver is installed.
The host VirtualBox has 3D acceleration enabled, of course. Max memory has been allocated, 128 M.
2D acceleration is also enabled, but it got enabled after I realized that hardware 3D was broken. It didn't seem to change anything.
I used four or five xorg.conf files. I tried using the default file, the modified default file (with vboxvideo written in its rightful place), the VirtualBox example file, an empty file, then using none. Nothing got virtual hardware 3D to work.
The virtualbox-guest-additions service is running.
Any idea for a fix?

