Fig. 6: Geometric comparison between SU benchmark and AIGC-generated results across three representative bias categories.

a Plan proportion bias, showing horizontal compression caused by the underestimation of the stage width-to-height ratio; b Vertical proportion bias, showing reduced second-storey elevation and compressed façade hierarchy; c Decorative component bias, showing the inflation of ornamental areas, particularly corridor screens. Red bounding boxes indicate the measurement regions used for ratio extraction and error quantification (see Table 4). All comparisons are based on rectified front-elevation views aligned with the SU coordinate system.