If you wonder, just as I just did, what the different options in the Advanced section of System Settings: Desktop: Desktop Effects: Advanced Options in KDE4 means, here is the answer:
- OpenGL is the fastest solution as it uses your graphics card's 3d acceleration for rendering.
- Texture from Pixmap is the fastest option, as it stores the texture directly in the graphics card's memory, which is usually faster than the system ram.
- Shared Memory stores the textures in X's shared memory, which resides in the system RAM and is usually much slower than the graphics card's memory.
- Fallback tries Texture from Pixmap first and Shared Memory if that does not work.
- XRender is less fast as it only uses 2d acceleration but much more compatible and works with older graphics cards as well.
The other options:
- Direct rendering passes the commands directly to the graphics card and bypasses the X server. This is much faster as it the commands have to be copied less, but can be more instable and less compatible.
- VSync stands for vertical synchrosation and ensures that the pictures are drawn in sync to the vertical display updates. This can be more soothing to the eyes, but is a little slower and just drawing the frames any time the graphics card is ready to do so.