OverLay++: Dense-Overlap Layout-to-Image Generation Dataset

Layout-to-Image generation has made substantial progress in image generation with spatial and object-level control. However, existing methods still struggle with complex scenes containing many overlapping and interacting objects. We argue that training data is a particular bottleneck: existing datasets lack examples with dense, complex, object interactions. To address this gap, we introduce **OverLay++**, a large-scale Layout-to-Image dataset with structurally complex scenes. OverLay++ contains approximately 500K images with an average of 6.6 objects per image, exceeding existing datasets by $1.67\times$ in annotation density. Beyond annotation density, OverLay++ provides rich semantic detail with object captions over six times longer than current datasets. Our dataset generation pipeline is simple and robust, producing accurate overlapping regions with rich per-object captions. Across multiple benchmarks, state-of-the-art Layout-to-Image methods trained on OverLay++ dataset show consistent improvement and faster convergence demonstrating the importance of dense, overlap-aware, and caption-rich supervision for controllable image generation.