To See a World in a Living Context:Unified Indoor-Outdoor Urban World Generation

Xiaobin Huang^1,*Zilong Huang^1,*Yang Luo¹Hongchao Fan²Yiping Chen^1,†Ting Han^1,†

¹ Sun Yat-sen University

² Norwegian University of Science and Technology

* Equal Contribution† Corresponding authors

Abstract

Text-driven 3D generation has advanced rapidly in creating large-scale outdoor environments and detailed indoor scenes, but these domains are usually synthesized independently, lacking the correspondence required for a coherent urban world. We present HoloWorld, a unified indoor-outdoor urban world generation framework built on a continuously updated cross-scale world context.

Initializing from a user description, HoloWorld progressively represents and updates the diverse world information, from city-scale planning to individual buildings, allowing generated interiors to maintain explicit correspondence with their associated exterior buildings. Conditioned on the evolving context and previously generated neighboring blocks, HoloWorld autoregressively generates urban exteriors with consistent spatial organization and visual identity across blocks. The generated exterior representations are further grounded in 3D building instances and footprints, enabling building-specific indoor generation with geometry-constrained layouts and inherited appearance characteristics.

To our knowledge, HoloWorld is the first framework to unify indoor and outdoor generation within a coherent 3D urban world. Extensive experiments demonstrate that HoloWorld achieves superior urban exterior generation performance, improving the average AQS score over the SOTA by 7.68% and obtaining the highest average RDR score, while maintaining strong building-level indoor-outdoor correspondence and cross-block continuity within a unified 3D urban world.

Method

World

Global identity, urban semantics, shared visual language.

Block

Local organization conditioned on surrounding city regions.

Building

A grounded instance with function, appearance, and footprint.

Interior

A corresponding space that belongs to its exterior building.

Overview of the HoloWorld generation pipeline — **Figure 2:** **Overview of HoloWorld.** (a) An evolving cross-scale world context organizes validated information at world, block, and building levels. (b) Context-driven outdoor generation and instance grounding localize this context to individual buildings, where it guides building-specific indoor synthesis under appearance, asset, and footprint constraints. (c) The resulting city, blocks, and interiors form explicitly corresponding parts of a unified 3D urban world.

Results

Qualitative comparison between HoloWorld and prior city generation methods — **Figure 3:** **Qualitative comparison under identical urban descriptions, with two views per scene.** HoloWorld generates richer architectural and landscape details while preserving more coherent spatial organization and visual style across the city.

Table 1: Quantitative comparison of urban exterior generation. All methods receive identical urban descriptions as inputs. GPT-5.5-based and human evaluations are reported separately. The best results are in bold.

Table 1: Quantitative comparison of urban exterior generation. All methods receive identical urban descriptions as inputs. GPT-5.5-based and human evaluations are reported separately. The best results are in bold.
Method	AQS								RDR
	SVC↑		SRC↑		MTF↑		LA↑		SVC↑		SRC↑		MTF↑		LA↑
	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.
CityCraft	7.11	7.17	7.22	6.00	4.89	5.00	5.89	5.00	23.65	19.21	20.76	19.61	19.90	14.99	17.35	15.97
SynCity	7.70	7.17	8.20	7.83	4.90	6.33	5.30	6.50	21.95	18.27	25.69	21.72	16.97	15.12	14.91	12.00
MajutsuCity	8.00	7.83	8.60	8.00	7.00	7.50	7.40	7.83	22.62	20.99	24.99	19.91	23.89	20.52	25.84	22.70
Ours	8.75	8.67	9.00	8.50	7.63	8.00	8.00	8.67	27.89	23.83	27.64	24.65	29.43	24.11	29.57	25.89

Table 2: Quantitative evaluation of building-level indoor–outdoor correspondence using GPT-5.5 and human evaluation. The best results are in bold. Dashes denote metrics unavailable for TRELLIS because its independently generated interior is not grounded in the exterior building footprint.

Table 2: Quantitative evaluation of building-level indoor-outdoor correspondence using GPT-5.5 and human evaluation. The best results are in bold. Dashes denote metrics unavailable for TRELLIS because its independently generated interior is not grounded in the exterior building footprint.
Method	AQS								RDR				Shape IoU↑
	Functional↑		Visual↑		Spatial↑		Average↑		Functional↑		Visual↑
	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.
TRELLIS	6.23	6.30	5.88	4.85	—	—	—	—	19.17	20.03	1.83	10.90	—
Ours	7.47	7.45	8.21	7.60	8.77	8.65	8.15	7.90	22.35	20.36	24.29	23.51	0.997

Table 3: Effect of dynamic world-context localization on building-level indoor–outdoor correspondence under GPT-5.5 and human evaluation. The best results are in bold.

Table 3: Effect of dynamic world-context localization on building-level indoor-outdoor correspondence under GPT-5.5 and human evaluation. The best results are in bold.
Configuration	AQS								RDR						Shape IoU↑
	Functional↑		Visual↑		Spatial↑		Average↑		Functional↑		Visual↑		Spatial↑
	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.	GPT	Hum.
Static World Context	5.75	5.88	4.58	6.00	3.25	4.75	4.53	5.54	16.37	11.75	1.40	0.33	1.40	11.09	0.670
Full Model	7.67	7.88	8.17	8.25	7.75	8.50	7.86	8.21	21.82	18.86	22.85	18.82	22.85	17.50	0.994

Table 4: Effect of autoregressive neighborhood conditioning (ANC) on cross-block visual and spatial continuity under GPT-5.5 and human evaluation. The best results are in bold.

Table 4: Effect of autoregressive neighborhood conditioning (ANC) on cross-block visual and spatial continuity under GPT-5.5 and human evaluation. The best results are in bold.
Configuration	Continuity AQS↑		RDR↑
Configuration	GPT	Hum.	GPT	Hum.
Full Model	8.25	7.75	24.04	21.97
w/o ANC	7.25	5.38	16.66	19.07

Generated Worlds

Complete Minecraft City generated by HoloWorld — 01 / 08FULL CITY OVERVIEW

Minecraft City local exterior rendered view 1 — LOCAL VIEW · 01

Minecraft City local exterior rendered view 2 — LOCAL VIEW · 02

Minecraft City interior dollhouse view — INTERIOR OVERVIEW

Minecraft City interior walkthrough view — INTERIOR VIEW

Complete Cyberpunk City generated by HoloWorld — 02 / 08FULL CITY OVERVIEW

Cyberpunk City local exterior rendered view 1 — LOCAL VIEW · 01

Cyberpunk City local exterior rendered view 2 — LOCAL VIEW · 02

Cyberpunk City interior dollhouse view — INTERIOR OVERVIEW

Cyberpunk City interior walkthrough view — INTERIOR VIEW

Complete European Old Town generated by HoloWorld — 03 / 08FULL CITY OVERVIEW

European Old Town local exterior rendered view 1 — LOCAL VIEW · 01

European Old Town local exterior rendered view 2 — LOCAL VIEW · 02

European Old Town interior dollhouse view — INTERIOR OVERVIEW

European Old Town interior walkthrough view — INTERIOR VIEW

Complete Ghibli City generated by HoloWorld — 04 / 08FULL CITY OVERVIEW

Ghibli City local exterior rendered view 1 — LOCAL VIEW · 01

Ghibli City local exterior rendered view 2 — LOCAL VIEW · 02

Ghibli City interior dollhouse view — INTERIOR OVERVIEW

Ghibli City interior walkthrough view — INTERIOR VIEW

Complete High-Density Modern City generated by HoloWorld — 05 / 08FULL CITY OVERVIEW

High-Density Modern City local exterior rendered view 1 — LOCAL VIEW · 01

High-Density Modern City local exterior rendered view 2 — LOCAL VIEW · 02

High-Density Modern City interior dollhouse view — INTERIOR OVERVIEW

High-Density Modern City interior walkthrough view — INTERIOR VIEW

Complete Candy-Pop Toy City generated by HoloWorld — 06 / 08FULL CITY OVERVIEW

Candy-Pop Toy City local exterior rendered view 1 — LOCAL VIEW · 01

Candy-Pop Toy City local exterior rendered view 2 — LOCAL VIEW · 02

Candy-Pop Toy City interior dollhouse view — INTERIOR OVERVIEW

Candy-Pop Toy City interior walkthrough view — INTERIOR VIEW

Complete Modern City generated by HoloWorld — 07 / 08FULL CITY OVERVIEW

Modern City local exterior rendered view 1 — LOCAL VIEW · 01

Modern City local exterior rendered view 2 — LOCAL VIEW · 02

Modern City interior dollhouse view — INTERIOR OVERVIEW

Modern City interior walkthrough view — INTERIOR VIEW

Complete Oceanic Civilization generated by HoloWorld — 08 / 08FULL CITY OVERVIEW

Oceanic Civilization local exterior rendered view 1 — LOCAL VIEW · 01

Oceanic Civilization local exterior rendered view 2 — LOCAL VIEW · 02

Oceanic Civilization interior dollhouse view — INTERIOR OVERVIEW

Oceanic Civilization interior walkthrough view — INTERIOR VIEW

Click the “Demo” button to explore the interactive HoloWorld demo.

Citation

@article{huang2026holoworld,
  title={To See a World in a Living Context: Unified Indoor-Outdoor Urban World Generation},
  author={Huang, Xiaobin and Huang, Zilong and Luo, Yang and Fan, Hongchao and Chen, Yiping and Han, Ting},
  journal={arXiv preprint arXiv:2608.05879},
  year={2026}
}

To See a World in a Living Context:Unified Indoor-Outdoor Urban World Generation

Abstract

Method

World

Block

Building

Interior

Results

Generated Worlds

Minecraft City

Cyberpunk City

European Old Town

Ghibli City

High-Density Modern City

Candy-Pop Toy City

Modern City

Oceanic Civilization

Citation