4 Guest Additions • 3D acceleration with Windows guests requires Windows 2000, Windows XP, Vista or Windows 7. Both OpenGL and Direct3D 8/9 (not with Windows 2000) are supported (experimental). • OpenGL on Linux requires kernel 2.6.27 and higher as well as X.org server version 1.5 and higher. Ubuntu 10.10 and Fedora 14 have been tested and confirmed as working. • OpenGL on Solaris guests requires X.org server version 1.5 and higher. 2. The Guest Additions must be installed. Note: For Direct 3D acceleration to work in a Windows Guest, VirtualBox needs to replace Windows system files in the virtual machine. As a result, the Guest Additions installation program offers Direct 3D acceleration as an option that must be explicitly enabled. Also, you must install the Guest Additions in “Safe Mode” see chapter 14, Known limitations, page 181 for details. 3. Because 3D support is still experimental at this time, it is disabled by default and must be manually enabled in the VM settings (see chapter 3.3, General settings, page 42). Note: Enabling 3D acceleration may expose security holes to malicious software running in the guest. The third-party code that VirtualBox uses for this purpose (Chromium) is not hardened enough to prevent every risky 3D operation on the host. Technically, VirtualBox implements this by installing an additional hardware 3D driver inside your guest when the Guest Additions are installed. This driver acts as a hardware 3D driver and reports to the guest operating system that the (virtual) hardware is capable of 3D hardware acceleration. When an application in the guest then requests hardware acceleration through the OpenGL or Direct3D programming interfaces, these are sent to the host through a special communication tunnel implemented by VirtualBox, and then the host performs the requested 3D operation via the host’s programming interfaces. 4.4.2 Hardware 2D video acceleration for Windows guests Starting with version 3.1, the VirtualBox Guest Additions contain experimental hardware 2D video acceleration support for Windows guests. With this feature, if an application (e.g. a video player) inside your Windows VM uses 2D video overlays to play a movie clip, then VirtualBox will attempt to use your host’s video acceler- ation hardware instead of performing overlay stretching and color conversion in software (which would be slow). This currently works for Windows, Linux and Mac host platforms, provided that your host operating system can make use of 2D video acceleration in the first place. The 2D video acceleration currently has the following preconditions: 1. It is only available for Windows guests (XP or later). 2. The Guest Additions must be installed. 3. Because 2D support is still experimental at this time, it is disabled by default and must be manually enabled in the VM settings (see chapter 3.3, General settings, page 42). Technically, VirtualBox implements this by exposing video overlay DirectDraw capabilities in the Guest Additions video driver. The driver sends all overlay commands to the host through a special communication tunnel implemented by VirtualBox. On the host side, OpenGL is then used to implement color space transformation and scaling 65