Looking Outside the Box to Ground Language in 3D Scenes



Existing language grounding models often use object proposal bottlenecks: a pre-trained detector proposes objects in the scene and the model learns to select the answer from these box proposals, without attending to the original image or 3D point cloud. Object detectors are typically trained on a fixed vocabulary of objects and attributes that is often too restrictive for open-domain language grounding, where an utterance may refer to visual entities at various levels of abstraction, such as a chair, the leg of a chair, or the tip of the front leg of a chair. We propose a model for grounding language in 3D scenes that bypasses box proposal bottlenecks with three main innovations: i) Iterative attention across the language stream, the point cloud feature stream and 3D box proposals. ii) Transformer decoders with non-parametric entity queries that decode 3D boxes for object and part referentials. iii) Joint supervision from 3D object annotations and language grounding annotations, by treating object detection as grounding of referential utterances comprised of a list of candidate category labels. These innovations result in significant quantitative gains (up to +9% absolute improvement on the SR3D benchmark) over previous approaches on popular 3D language grounding benchmarks. We ablate each of our innovations to show its contribution to the performance of the model. When applied on language grounding on 2D images with minor changes, it performs on par with the state-of-the-art while converges in half of the GPU time.

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