## 7 Conclusions  
Within the context of urban regeneration and district redevelopment initiatives, analyzing the spatial differentiation patterns and formation mechanisms of urban vitality from a multi-scale perspective holds significant theoretical value and practical significance for the assessment and revitalization of cities. This research innovatively employs multi-source data to provide urban planners and policymakers with an effective framework for evaluating urban vitality, offering a replicable model for other cities. By integrating big data, this study quantitatively assesses the economic, social and cultural vitality of central Qingdao and characterizes the spatial distribution and clustering patterns of urban vitality at both subdistrict and block scales. Through the development of a comprehensive 5D built environment indicator system, this study quantifies environmental impact factors and employs the OPGD and MGWR models to elucidate the mechanisms through which the built environment influences urban vitality. The findings provide evidence-based strategies for both micro-scale vitality optimization and macro-level urban quality enhancement, offering valuable references for future urban development initiatives. The principal conclusions are as follows:  
(1) Urban vitality in central Qingdao displays a spatial structure characterized by a \"weak east-west, strong central, multi-center, cluster-structured\" pattern, with higher vitality predominantly concentrated in the core of the central area and diminishing unevenly in clustered patterns radiating outward from the business district core. The vitality pole located in the southern sector of the central area is well established, whereas smaller vitality poles in the northern and southeastern regions are still developing and require further efforts to enhance their attractiveness. (2) The distribution of urban vitality exhibits significant spatial autocorrelation. At the subdistrict scale, high-high vitality clusters are concentrated within the central urban districts of Shinan and Shibei, gradually extending from the core toward peripheral areas, and low-low vitality clusters are primarily located distributed in the northern and southwestern parts of Guangdong District, Chengyang District and the northern section of Licang District. At the block scale, new patterns of high-high and low-low clusters have emerged, building upon the spatial distribution observed at the subdistrict scale. (3) Urban vitality aggregation arises from the combined effects of multiple factors, with interactions between any two factors exerting a significantly greater influence than individual factors alone. Notably, the interaction between the three factors of functional density, commercial facilities accessibility and public facilities accessibility and other factors constitutes the primary determinant influencing urban vitality intensity at both scales. The interaction between building density and morphological compactness exhibits the least influence at the subdistrict scale, while at the block scale, the interaction between morphological compactness, resident population density and greening rate exerts the lowest impact. (4) The impact of individual factors on urban vitality varies considerably across different spatial variability. The indicators most positively correlated with urban vitality are commercial facilities accessibility and cultural and leisure facilities accessibility. A moderate increase in building height promotes urban vitality, while resident population density exerts both positive and negative effects on urban vitality at the subdistrict scale, while it has a predominantly negative impact on urban vitality at the block scale. In addition to the aforementioned factors, other dimensions such as density, design and distance to transit positively contribute to urban vitality at the block scale, playing a significant role in its enhancement.