Novel View Synthesis of Structural Color Objects Created by Laser Markings

Novel View Synthesis of Structural Color Objects Created by Laser Markings

Abstract

Transforming physical object into its high quality 3D digital twin using novel view synthesis is crucial for researchers in the domain of automatic laser marking of any color image on different metal substrates. Current Radiance Field methods have significantly advanced novel view synthesis of scenes captured with multiple photos or videos. But, they struggle to represent the scene with shiny objects. Moreover, multi view reconstruction of reflective objects with structural colors is extremely challenging because specular reflections are view-dependent and thus violate the multiviewconsistency, which is the cornerstone for most multiview reconstruction methods. However, there is a general lack of synthetic datasets for objects with structural colors and a literature review on state-of-the-art (SOTA) novel view synthesis methods for this kind of materials. Addressing these issues, we introduce a novel synthetic dataset that is used to conduct quantitative and qualitative analysis on a SOTA novel view synthesis methods. We demonstrate different techniques to improve the scene representation of laser printed planar structural color objects, focusing on the 3D Gaussian Splatting (3D-GS) method, which performs exceptionally well on our synthetic dataset. Our techniques, such as using geometric prior of planar structural color objects while initializing scene with sparse structure-from-motion (SfM) point cloud and the Anisotropy Regularizer, significantly improves the visual quality of view synthesis. We design different capture setups to acquire images of objects and evaluate the visual quality of the scene with different capture setups. Additionally, we present comprehensive experimentation to demonstrate methods to simulate structural color objects using just captured images of laser-printed primaries. This comprehensive research aims to contribute to the advancement of novel view synthesis methods for scenes involving reflective objects with structural colors.

TLDR

This work is the result of my master thesis on “Novel View Synthesis of Structural Color Objects Created by Laser Markings”, in collaboration with AIDAM, Oraclase, MPI-Inf, and SIC.

This work marks the beginning of Novel View Synthesis (NVS) of structural color objects and opens up potential avenues for various future research directions and endeavors.

Beginners: This thesis will help beginners grasp the brief history of radiance field methods and essential preliminaries, such as the mathematics, tools, and concepts necessary to understand NVS methods. Furthermore, it will serve as a foundational guide for novice researchers interested in exploring the novel view synthesis of specular and shiny objects with high view-dependent colors, commonly referred to as Structural Colors or Pearlescent Colors.

Advanced Researchers: This thesis will also be a valuable reference for advanced researchers who may wish to revisit the fundamental concepts and access the StructColorToaster scene from new Structural Color Blender Dataset. Additionally, the thesis discusses approaches to improve results and outlines potential future research directions.

Technical Artists: This thesis provides an overview of how the new Gaussian Splatting technology can be applied to various use cases and demonstrates the life cycle of a specific use case in interactive product visualization, from capturing the product to visualizing it in a web viewer.

Datasets

  • Structural Color Blender Dataset (Synthetic Scenes)

    • StructColorToaster Scene: Access Blender source and dataset from 👉here
  • Real Scenes

    • StructColorPainting Scene
    • StructColorPaintingOld Scene
    • StructColorPrimaries Scene
    • StructColorTaylorSwift Scene

Evaluation

Structural Color Blender Dataset (Synthetic Scenes)

  • Evaluation of selected SOTA methods on StructColorToaster scene:
MethodIterationsPSNR ↑SSIM ↑LPIPS ↓TrainFPSMemory
NeRF50K23.3590.84270.18951 day0.00122MB
InstantNGP50K19.6590.81090.206823 min6159.2MB
Mip-NeRF250K22.8180.8770.12631 day0.0315.9MB
NeRFacto50K19.3050.80560.212335 min0.6168MB
Ref-NeRF250K27.51940.91420.12862 days0.38.2MB
3D-GS30K24.04350.90650.106120 min14077MB
3D-GS60K24.31170.90700.105230 min14077MB
Table 1: Quantitative evaluation of selected methods' results computed over our StructColorToaster Scene.
(The values for the Train time and FPS are approximate.)
  • Renders of optimized StructColorToaster Scene using 3D-GS:
    Figure 1: The renderings show that 3D-GS able to capture the crisp shininess appearance of the surface. However, it does improve in learning specular reflections with increasing iterations, it is still not up to the mark and suffures from  holes and aliasing effect aka popping artifacts.

    Figure 1: The renderings show that 3D-GS able to capture the crisp shininess appearance of the surface. However, it does improve in learning specular reflections with increasing iterations, it is still not up to the mark and suffures from holes and aliasing effect aka popping artifacts.

Real Scenes

  • Evalution of different choices on StructColorPainting and StructColorPaintingOld Scenes
Method7K30K
Vanilla 3D-GS27.1128.92
Cleaned-SfM27.671529.1789
With-Masks9.3529.4603
With-Cropped-Images/RGBA Images29.175930.0007
With-Cropped-Images/RGBA Images:
(No-Densification + No-Position Optimization)
24.461225.089
Densify Until Iteration = 3000026.832529.4149
Densification Interval = 3025.263428.6454
Densification Interval = 5026.018928.2718
Reset Opacity = Every 1000 Iteration27.721629.2581
Reset Opacity = Every 2000 Iteration27.635429.1786
Reset Opacity = Every 5000 Iteration27.8229.2726
SH-Degree 026.469927.9771
White-Background27.657929.2025
Random-Background27.760729.3303
No-Densification17.791918.3929
Reduced Number of Images = 29727.365728.7223
Anisotropy-Regularizer27.574729.4191
Table 2: PSNR Score for ablation runs. Quantitative evaluation of results computed over our StructColorPainting scene using different 3D-GS settings. (The values for FPS are approximate.)
  • Evaluation of selected techniques’ results computed over our StructColorPainting scene:
MethodIterationsPSNR ↑SSIM ↑LPIPS ↓TrainFPSMemory
Cleaned-SfM7K27.64520.92210.17955.122min15079MB
30K29.17890.93420.160227.69min120150MB
Anisotropy-Regularizer7K27.54760.92230.17805.134min15078.6MB
30K29.96310.93460.157226.35 min120152.4MB
Anisotropy-Regularizer:
297-Images
7K26.99200.92380.18335.812 min15086.1MB
30K29.32130.93390.164828.57min120176.2MB
Table 3: Quantitative evaluation of selected techniques’ results computed over our StructColorPainting scene. (The values for FPS are approximate).
  • Evaluation of renderings using our techniques’ and gsplat with cleaned SfM and additional features computed over StructColorTaylorSwift scene:
MethodIterationsPSNR ↑SSIM ↑LPIPS ↓TrainFPSMemory
Our Techniques7K30.25670.93380.19214.123min15055MB
30K33.65470.94580.174918.5min12094MB
gsplat7K31.80510.93910.18802.86min15064MB
30K34.64510.95110.165816.61min120119MB
gsplat + Mip-Splatting7K31.35280.93620.19222.54min15066MB
30K34.66540.93790.182717.1min120124MB
Table 4: Quantitative evaluation of selected techniques’ results computed over our StructColorPainting scene. (The values for FPS are approximate.)

Videos

Real Scenes

RGB renders of interactive visualization in SIBR viewer of an optimized real world sences with our techniques:

  • StructColorPainting scene

  • StructColorTaylorSwift scene


Synthesized Scenes Using Just Primaries

  • Simulating Structural Color Object (Pseudo) before Laser Printing:
Figure 2: Pipeline of Synthesizing Arbitrary Images of Structural Color Object for Arbitrary Viewing Directions.

Figure 2: Pipeline of Synthesizing Arbitrary Images of Structural Color Object for Arbitrary Viewing Directions.

  • Comparison between real structural color object views and respective synthesized views using just primaries for respective view directions:
    • StructColorTaylorSwift scene

    • RGB renders of interactive visualization in SIBR viewer of an optimized synthetic scene, generated using synthesized images created just with primaries:


  • Synthesizing views using only the earlier tracked primaries for respective view directions, before laser printing the structural color object:
    • Synthesized views using just primaries for respective view directions:

    • RGB renders of interactive visualization in SIBR viewer of an optimized synthetic scene, generated using synthesized images created just with primaries:

3D Web Viewer

StructColorPaintingViewer is a webviwer to visulaize the structural color objects. The webviewer is implemented with help of gsplat.js but it only supports scenes optimized with spherical harmonics (SH) of degree 0. However, scenes optimized with SH0 don’t achieve the same quality as those optimized with SH3, which is evident from above videos of renderings of scenes optimized with SH3 in SIBR viewer.

BibTeX

References

1. [NeRF] Ben Mildenhall, Pratul P. Srinivasan, Matthew Tancik, Jonathan T. Barron, Ravi Ramamoorthi, and Ren Ng. Nerf: Representing scenes as neural radiance fields for view synthesis. ECCV, 2020.
2. [InstantNGP] Thomas Muller, Alex Evans, Christoph Schied, and Alexander Keller. Instant neural graphics primitives with a multiresolution hash encoding. ACM Trans.Graph., July 2022.
3. [Mip-NeRF] Jonathan T. Barron, Ben Mildenhall, Matthew Tancik, Peter Hedman, Ricardo Martin-Brualla, and Pratul P. Srinivasan. Mip-nerf: A multiscale representation for anti-aliasing neural radiance fields. ICCV, 2021.
4. [NeRFacto] Matthew Tancik, Ethan Weber, Evonne Ng, Ruilong Li, Brent Yi, Justin Kerr, Terrance Wang, Alexander Kristoffersen, Jake Austin, Kamyar Salahi, Abhik Ahuja, David McAllister, and Angjoo Kanazawa. Nerfstudio: A modular framework for neural radiance field development. ACM SIGGRAPH 2023.
5. [Ref-NeRF] Dor Verbin, Peter Hedman, Ben Mildenhall, Todd Zickler, Jonathan T. Barron, and Pratul P. Srinivasan. Ref-NeRF: Structured view-dependent appearance for neural radiance fields. CVPR, 2022.
6. [3D-GS] Bernhard Kerbl, Georgios Kopanas, Thomas Leimkuehler, and George Drettakis. 3d gaussian splatting for real-time radiance field rendering. ACM Transactions on Graphics, July 2023.