  Recent advances in diffusion models such as ControlNet have enabled
geometrically controllable, high-fidelity text-to-image generation. However,
none of them addresses the question of adding such controllability to
text-to-3D generation. In response, we propose Text2Control3D, a controllable
text-to-3D avatar generation method whose facial expression is controllable
given a monocular video casually captured with hand-held camera. Our main
strategy is to construct the 3D avatar in Neural Radiance Fields (NeRF)
optimized with a set of controlled viewpoint-aware images that we generate from
ControlNet, whose condition input is the depth map extracted from the input
video. When generating the viewpoint-aware images, we utilize cross-reference
attention to inject well-controlled, referential facial expression and
appearance via cross attention. We also conduct low-pass filtering of Gaussian
latent of the diffusion model in order to ameliorate the viewpoint-agnostic
texture problem we observed from our empirical analysis, where the
viewpoint-aware images contain identical textures on identical pixel positions
that are incomprehensible in 3D. Finally, to train NeRF with the images that
are viewpoint-aware yet are not strictly consistent in geometry, our approach
considers per-image geometric variation as a view of deformation from a shared
3D canonical space. Consequently, we construct the 3D avatar in a canonical
space of deformable NeRF by learning a set of per-image deformation via
deformation field table. We demonstrate the empirical results and discuss the
effectiveness of our method.
