In Ecdesign 4.5 you can customize your real-time 3D quality using the 3-star system found in the top toolbar when in 3D. Choose 1 or 2 stars (low-medium quality) if using a computer lacking good graphics card. This will remove some of the real-time 3D effects and as a result increase the FPS (Frames per second).
Ecdesign will automatically save images and walkthrough videos in the highest quality (3rd star). The star system only controls the real-time 3D (when walking in 3D).