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Direct2.5: Diverse Text-to-3D Generation via Multi-view 2.5D Diffusion
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Fine-tunes Stable Diffusion 2.1 into a multi-view normal-map diffusion model, fuses four generated normal maps into a mesh via space carving and differentiable rasterization, then generates normal-conditioned multi-view textures for text-to-3D in about 10 seconds.
Problem
Text-to-3D generation is slow and mode-seeking when based on score distillation sampling, while direct 3D diffusion trained on limited 3D data generalizes poorly and loses diversity.
Approach
Fine-tune a pre-trained 2D latent diffusion model to jointly generate multi-view 2.5D normal maps with cross-view self-attention and co-train with 2D image data, then reconstruct geometry from only four normal views by space-carving initialization and differentiable rasterization, avoiding SDS entirely.
Key results
- Achieves FID 82.3 on Objaverse renderings versus 117.7 for MVDream and 125.9 for DreamFusion, with about 10 s runtime versus about 35 min for MVDream.
- Reports IS 8.111 and CLIP 0.267, close to MVDream (8.180 and 0.262) and better than Point-E and Shap-E on all metrics.
- Ablation: removing 2D joint training raises normal-model FID from 36.08 to 43.61, showing the value of the large-scale image data.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| add joint training on large-scale 2D images to text-to-normal training (ablation) | Direct2.5 T2N · Objaverse normal renderings | FID: 43.61 -> 36.08 | Helped |
| add joint training on large-scale 2D images to text-to-normal training (ablation) | Direct2.5 T2N · Objaverse normal renderings | IS: 8.94 -> 9.39 | Helped |
| add joint training on large-scale 2D images to text-to-normal training (ablation) | Direct2.5 T2N · Objaverse normal renderings | CLIP score: 0.270 -> 0.289 | Helped |
| use fewer, higher text-consistency 3D training subjects (ablation) | Direct2.5 T2N · Objaverse normal renderings | FID: 36.08 -> 37.29 | Hurt |
| use fewer, higher text-consistency 3D training subjects (ablation) | Direct2.5 T2N · Objaverse normal renderings | IS: 9.39 -> 9.44 | Helped |
| use fewer, higher text-consistency 3D training subjects (ablation) | Direct2.5 T2N · Objaverse normal renderings | CLIP score: 0.289 -> 0.294 | Helped |
| use Direct2.5 instead of MVDream | text-to-3D generation · DreamFusion prompts | IS: 8.180 -> 8.111 | Hurt |
| use Direct2.5 instead of MVDream | text-to-3D generation · DreamFusion prompts | CLIP score: 0.262 -> 0.267 | Helped |
| use Direct2.5 instead of MVDream | text-to-3D generation · DreamFusion prompts, Objaverse | FID: 117.715 -> 82.324 | Helped |
| use Direct2.5 instead of MVDream | text-to-3D generation · DreamFusion prompts, COCO validation set | FID: 133.089 -> 126.014 | Helped |
Surprising findings
- Fine-tuning only on multi-view 3D normal data without 2D image co-training causes catastrophic forgetting and a clear FID degradation.
Limitations
- Only four views limit observation of the top, bottom and concave regions, so these cannot be reconstructed well.
- Texture realism is degraded by the quality of the Objaverse training renderings.
- Texture refinement needs iterative inpainting to cover unseen areas.
Experimental setup
Datasets: Objaverse Cap3D captions COYO-700M
Benchmarks: DreamFusion prompts (50 prompts) Objaverse renderings (2000 subjects) COCO validation
Metrics: FID IS CLIP score run time
Baselines: DreamFusion Fantasia3D MVDream Point-E Shap-E ProlificDreamer
Builds on: Stable Diffusion MVDream Zero-1-to-3 DreamFusion nvdiffrast
Closest papers by meaning
- DIRECT-3D: Learning Direct Text-to-3D Generation on Massive Noisy 3D Data (CVPR 2024 · similarity 0.91)
- MVDream: Multi-view Diffusion for 3D Generation (ICLR 2024 · similarity 0.91)
- IT3D: Improved Text-to-3D Generation with Explicit View Synthesis (AAAI 2024 · similarity 0.90)
- EfficientDreamer: High-Fidelity and Robust 3D Creation via Orthogonal-view Diffusion Priors (CVPR 2024 · similarity 0.90)
- Diffusion$^2$: Dynamic 3D Content Generation via Score Composition of Video and Multi-view Diffusion Models (ICLR 2025 · similarity 0.90)
- Sharp-It: A Multi-view to Multi-view Diffusion Model for 3D Synthesis and Manipulation (CVPR 2025 · similarity 0.90)
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