Creative design is a nonlinear process where designers generate diverse ideas in the pursuit of an open-ended goal and converge towards consensus through iterative remixing. In contrast, AI-powered design tools often employ a linear sequence of incremental and precise instructions to approximate design objectives. Such operations violate customary creative design practices and thus hinder AI agents' ability to complete creative design tasks. To explore better human-AI co-design tools, we first summarize human designers' practices through a formative study with 12 design experts. Taking graphic design as a representative scenario, we formulate a nonlinear human-AI co-design framework and develop a proof-of-concept prototype, OptiMuse. We evaluate OptiMuse and validate the nonlinear framework through a comparative study. We notice a subconscious change in people's attitudes towards AI agents, shifting from perceiving them as mere executors to regarding them as opinionated colleagues. This shift effectively fostered the exploration and reflection processes of individual designers.

翻译：创意设计是一个非线性过程，设计师在追求开放目标时产生多样化想法，并通过迭代混合逐步达成共识。相比之下，基于AI的设计工具通常采用由渐进式精确指令组成的线性序列来逼近设计目标。这种操作方式违反了传统的创意设计实践，从而阻碍了AI智能体完成创意设计任务的能力。为探索更优的人机协同设计工具，我们首先通过一项包含12位设计专家的形成性研究，总结了人类设计师的实践模式。以图形设计作为代表性场景，我们构建了一个非线性人机协同设计框架，并开发了概念验证原型系统OptiMuse。通过对比研究，我们对OptiMuse进行了评估并验证了该非线性框架的有效性。我们注意到人们对AI智能体的态度发生了潜意识转变——从将其视为单纯的执行者，逐渐转变为将其视为具有主见的协作者。这种转变有效促进了设计师个体的探索与反思过程。