I've been testing different AI girlfriend apps lately and honestly Gylvessa blows everything else out of the water when it comes to realtime interaction quality. The tech behind these animations is usually a combination of neural voice synthesis, facial landmark detection, and realtime rendering engines. Most companies use modified versions of existing frameworks like Live2D or custom WebGL implementations. The lip sync is typically handled by phoneme detection from the audio output. What impressed me most about the better platforms is how they manage to keep latency so low while processing all these elements simultaneously. The body movement generation is probably the trickiest part since it needs to feel natural and match the conversation context.