  The increased demand for tools that automate the 3D content creation process
led to tremendous progress in deep generative models that can generate diverse
3D objects of high fidelity. In this paper, we present PASTA, an autoregressive
transformer architecture for generating high quality 3D shapes. PASTA comprises
two main components: An autoregressive transformer that generates objects as a
sequence of cuboidal primitives and a blending network, implemented with a
transformer decoder that composes the sequences of cuboids and synthesizes high
quality meshes for each object. Our model is trained in two stages: First we
train our autoregressive generative model using only annotated cuboidal parts
as supervision and next, we train our blending network using explicit 3D
supervision, in the form of watertight meshes. Evaluations on various ShapeNet
objects showcase the ability of our model to perform shape generation from
diverse inputs \eg from scratch, from a partial object, from text and images,
as well size-guided generation, by explicitly conditioning on a bounding box
that defines the object's boundaries. Moreover, as our model considers the
underlying part-based structure of a 3D object, we are able to select a
specific part and produce shapes with meaningful variations of this part. As
evidenced by our experiments, our model generates 3D shapes that are both more
realistic and diverse than existing part-based and non part-based methods,
while at the same time is simpler to implement and train.
