DiT-3D: Exploring Plain Diffusion Transformers for 3D Shape Generation
Authors: name: Shentong Mo, name: Enze Xie, name: Ruihang Chu, name: Lewei Yao, name: Lanqing Hong, name: Matthias Nießner, name: Zhenguo Li

Recent Diffusion Transformers (e.g., DiT) have demonstrated their powerful
effectiveness in generating high-quality 2D images. However, it is still being
determined whether the Transformer architecture performs equally well in 3D
shape generation, as previous 3D diffusion methods mostly adopted the U-Net
architecture. To bridge this gap, we propose a novel Diffusion Transformer for
3D shape generation, namely DiT-3D, which can directly operate the denoising
process on voxelized point clouds using plain Transformers. Compared to
existing U-Net approaches, our DiT-3D is more scalable in model size and
produces much higher quality generations. Specifically, the DiT-3D adopts the
design philosophy of DiT but modifies it by incorporating 3D positional and
patch embeddings to adaptively aggregate input from voxelized point clouds. To
reduce the computational cost of self-attention in 3D shape generation, we
incorporate 3D window attention into Transformer blocks, as the increased 3D
token length resulting from the additional dimension of voxels can lead to high
computation. Finally, linear and devoxelization layers are used to predict the
denoised point clouds. In addition, our transformer architecture supports
efficient fine-tuning from 2D to 3D, where the pre-trained DiT-2D checkpoint on
ImageNet can significantly improve DiT-3D on ShapeNet. Experimental results on
the ShapeNet dataset demonstrate that the proposed DiT-3D achieves
state-of-the-art performance in high-fidelity and diverse 3D point cloud
generation. In particular, our DiT-3D decreases the 1-Nearest Neighbor Accuracy
of the state-of-the-art method by 4.59 and increases the Coverage metric by
3.51 when evaluated on Chamfer Distance.