Organizations: Singapore–MIT Alliance for Research and Technology Centre (SMART), Singapore · Department of Urban Planning, Tsinghua University, Beijing, China · Department of Urban Studies and Planning, Massachusetts Institute of Technology, Cambridge, MA, USA · College of Urban and Environmental Sciences, Peking University, Beijing, China · Department of Urban and Regional Planning, University of Florida, Gainesville, FL, USA · Stanford Institute for Human-Centered Artificial Intelligence, Stanford University, Stanford, USA
Urban development has been a defining force in human history, shaping cities for centuries. However, past studies mostly analyze such development as predictive tasks, failing to reflect its generative nature. Therefore, this study designs a multimodal generative AI framework to envision sustainable urban development at a global scale. By integrating prompts and geospatial controls, our framework can generate high-fidelity, diverse, and realistic urban satellite imagery across the 500 largest metropolitan areas worldwide. It enables users to specify urban development goals, creating new images that align with them while offering diverse scenarios whose appearance can be controlled with text prompts and geospatial constraints. It also facilitates urban redevelopment practices by learning from the surrounding environment. Beyond visual synthesis, we find that it encodes and interprets latent representations of urban form for global cross-city learning, successfully transferring styles of urban environments across a global spatial network. The latent representations can also enhance downstream prediction tasks such as carbon emission prediction. Further, human expert evaluation confirms that our generated urban images are comparable to real urban images. Overall, this study presents innovative approaches for accelerated urban planning and supports scenario-based planning processes for worldwide cities.
Figures & tables
Figure 1: Spatial heterogeneity of population density and building volume density for global 500 cities. a. City-level global population density. b. Distribution of population density across 500 cities, sorted in ascending order. c. City-level global building volume density. d. Distribution of building volume density across 500 cities, sorted in ascending order. In a and c , the city-level densities are divided into five qualitative levels, where warm (orange and red) and cool colors (green and slight green) refer to high and low densities, respectively. In b and d , each dot corresponds to a city and is color-coded by continent (Europe, Asia, North America, South America, Oceania, and Africa). Representative cities, including Boston, Stockholm, Kigali, Singapore, and Hong Kong, are highlighted for reference.
Figure 2: Multi-modal conditional counterfactual synthesis of urban satellite imagery. a . Generated images respond to counterfactual template texts. The first row shows three generated images from the density metric prompt, and the second row shows three generated images from the land use prompt. b . Generated images respond to free-form texts. c . Urban redevelopment with the image inpaint model. d . Generative fidelity, precision and diversity performance of our framework.
Figure 3: Cross-city learning through generative urban visualization. a . Generated satellite images across cities from the source city (e.g., Hong Kong, Lusaka). b . Performance variation across regions. c . Human evaluation of our framework by urban experts. 42 urban experts (from the United States, Singapore, China, etc.; from both academia and industry) were recruited to rate (1-10 scores) for 136 questions. The generated urban images are comparable to those of real urban images.
Figure 4: Our framework quantifies urban visuals in latent space. a . Our framework has learned a distinguishable visual representation for each city. other city’s results can be found in SI. b . Cross-city transfer via prompt modification from “Stockholm” to “Stockholm from Kigali” yields hybrid satellite imagery, with latent features (black points) located between Kigali and Stockholm clusters. c . Performance comparison of predicted versus true global fossil fuel carbon emission for ResNet and DINOv3, using original data (top) and generative augmentation (bottom).
Extended Data Fig. 1 Modeling diagram of our framework.
Extended Data Fig. 2 Multi-modal (text-image) conditional counterfactual synthesis of urban satellite imagery in Kigali and Stockholm cities. a . Generated images respond to counterfactual texts in Kigali City. b . Generated images respond to counterfactual texts in Stockholm City. The first row shows three generated images from the density metric prompt, and the second row shows three generated images from the land use prompt.
Extended Data Fig. 3 Multi-modal (text-image) conditional counterfactual synthesis of urban satellite imagery in Chicago and Tampa cities. a . Generated images respond to counterfactual texts in Chicago City. b . Generated images respond to counterfactual texts in Tampa City. The first row shows three generated images from the density metric prompt, and the second row shows three generated images from the land use prompt.
Extended Data Fig. 4. Examples of reader study. a . An example question for urban experts to evaluate generated urban image in the urban density dimension. b . An example question for urban experts to evaluate generated urban redevelopment image.
Figure S1 : Relationship between Density Metrics
Figure S2 : Generated urban imagery responds to prompts and constraints. a . Generated images respond to different environmental constraints and text b . Generated imagery is diverse under the same control. RPD: residential population density; RVC: residential volume per capita; BVD: building volume density; BCR: building coverage ratio; Land use ratios: residential, commercial, industrial, etc.
Models
Steps
Params
Fidelity
Diversity
Precision
FID ↓
PSNR ↑
SSIM ↓
FSIM ↓
SSIM ↑
FSIM ↑
LPIPS ↓
MS-SSIM ↑
Baselines
Original SD (No finetuning)
0
1.4B
86.5
10.56±0.9
–
–
0.0927±0.008
0.5556±0.024
0.7162±0.045
0.0978±0.007
ControlNet
60k
1.4B
76.5
10.94±2.2
0.1847±0.13
0.5802±0.06
0.1087±0.07
0.5603±0.04
0.5623±0.038
0.1179±0.044
Few Steps
UCN+CLIP
20k
1.5B
72.5
10.58±2.3
0.1665±0.08
0.5560±0.04
0.1235±0.06
0.5545±0.035
0.5808±0.041
0.1120±0.048
Table S1: Quantitative assessment of image fidelity, diversity, and precision metrics
Experiment
BCR
BVD
MAE ↓
R2↑
MAE ↓
R2↑
UrbanControlNet
171.525
0.619
6.186
0.871
Table S2 : Prediction performance of a pre-trained CNN on Dtest and on synthetic SAIs generated using the models listed in the experiment column
Figure S3 : Text-constraint-conditional counterfactual synthesis of urban satellite imagery . a . Generated images respond to counterfactual density inputs. b . Generated images respond to free-form texts.
Figure S4 : Multi-source pseudo-Siamese network in UrbanControlNet.
Figure S5 : Numeral-aware network in UrbanControlNet.
Figure S6 : Model performance (R 2 ) distribution across more than 100 cities globally.
Model
R2(log)↑
R2↑
MAE ↓
RMSE ↓
ResNet
0.830
0.610
22.04
60.82
ResNet+TradAug
0.837
0.630
21.74
57.72
ResNet+AutoAug [ 8 ]
0.842
0.626
21.45
58.53
ResNet+SARandAug [ 36 ]
0.834
0.634
21.69
57.79
ResNet+GA
0.879
0.696
18.42
52.86
Swin Transformer
0.874
0.690
19.01
53.73
Table S3 : Performance comparison of different models for global fossil fuel carbon emission prediction.
Department of Urban and Regional Planning, University of Florida · Singapore-MIT Alliance for Research and Technology Centre (SMART) · Department of Landscape Architecture and Urban Planning, Texas A&M University +1