ViPlan: A Benchmark for Visual Planning with Symbolic Predicates and
  Vision-Language Models
Authors: name: Matteo Merler, name: Nicola Dainese, name: Minttu Alakuijala, name: Giovanni Bonetta, name: Pietro Ferrazzi, name: Yu Tian, name: Bernardo Magnini, name: Pekka Marttinen

Integrating Large Language Models with symbolic planners is a promising
direction for obtaining verifiable and grounded plans compared to planning in
natural language, with recent works extending this idea to visual domains using
Vision-Language Models (VLMs). However, rigorous comparison between
VLM-grounded symbolic approaches and methods that plan directly with a VLM has
been hindered by a lack of common environments, evaluation protocols and model
coverage. We introduce ViPlan, the first open-source benchmark for Visual
Planning with symbolic predicates and VLMs. ViPlan features a series of
increasingly challenging tasks in two domains: a visual variant of the classic
Blocksworld planning problem and a simulated household robotics environment. We
benchmark nine open-source VLM families across multiple sizes, along with
selected closed models, evaluating both VLM-grounded symbolic planning and
using the models directly to propose actions. We find symbolic planning to
outperform direct VLM planning in Blocksworld, where accurate image grounding
is crucial, whereas the opposite is true in the household robotics tasks, where
commonsense knowledge and the ability to recover from errors are beneficial.
Finally, we show that across most models and methods, there is no significant
benefit to using Chain-of-Thought prompting, suggesting that current VLMs still
struggle with visual reasoning.