Flow-based generative models have highly desirable properties like exact log-likelihood evaluation and exact latent-variable inference, however they are still in their infancy and have not received as much attention as alternative generative models. In this paper, we introduce C-Flow, a novel conditioning scheme that brings normalizing flows to an entirely new scenario with great possibilities for multi-modal data modeling. C-Flow is based on a parallel sequence of invertible mappings in which a source flow guides the target flow at every step, enabling fine-grained control over the generation process. We also devise a new strategy to model unordered 3D point clouds that, in combination with the conditioning scheme, makes it possible to address 3D reconstruction from a single image and its inverse problem of rendering an image given a point cloud. We demonstrate our conditioning method to be very adaptable, being also applicable to image manipulation, style transfer and multi-modal image-to-image mapping in a diversity of domains, including RGB images, segmentation maps, and edge masks.

通过引入一种新的条件方案C-Flow，该研究将基于流的生成模型扩展到了全新的场景，针对多模态数据建模，包括图像、分割图和边缘掩膜等。还针对无序3D点云建立了新的策略，并针对三维重建、图像渲染和多模态图像之间的映射提出了应用，以及实现了高度可适应性的应用。

C-Flow：用于图像和3D点云的条件生成流模型