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Shadowless Projection Mapping for Tabletop Workspaces with Synthetic Aperture Projector

Takahiro Okamoto, Masaki Takeuchi, Masataka Sawayama, Daisuke Iwai

Abstract

Projection mapping (PM) enables augmented reality (AR) experiences without requiring users to wear head-mounted displays and supports multi-user interaction. It is regarded as a promising technology for a variety of applications in which users interact with content superimposed onto augmented objects in tabletop workspaces, including remote collaboration, healthcare, industrial design, urban planning, artwork creation, and office work. However, conventional PM systems often suffer from projection shadows when users occlude the light path. Prior approaches employing multiple distributed projectors can compensate for occlusion, but suffer from latency due to computational processing, degrading the user experience. In this research, we introduce a synthetic-aperture PM system that uses a significantly larger number of projectors, arranged densely in the environment, to achieve delay-free, shadowless projection for tabletop workspaces without requiring computational compensation. To address spatial resolution degradation caused by subpixel misalignment among overlaid projections, we develop and validate an offline blur compensation method whose computation time remains independent of the number of projectors. Furthermore, we demonstrate that our shadowless PM plays a critical role in achieving a fundamental goal of PM: altering material properties without evoking projection-like impression. Specifically, we define this perceptual impression as ``sense of projection (SoP)'' and establish a PM design framework to minimize the SoP based on user studies.

Shadowless Projection Mapping for Tabletop Workspaces with Synthetic Aperture Projector

Abstract

Projection mapping (PM) enables augmented reality (AR) experiences without requiring users to wear head-mounted displays and supports multi-user interaction. It is regarded as a promising technology for a variety of applications in which users interact with content superimposed onto augmented objects in tabletop workspaces, including remote collaboration, healthcare, industrial design, urban planning, artwork creation, and office work. However, conventional PM systems often suffer from projection shadows when users occlude the light path. Prior approaches employing multiple distributed projectors can compensate for occlusion, but suffer from latency due to computational processing, degrading the user experience. In this research, we introduce a synthetic-aperture PM system that uses a significantly larger number of projectors, arranged densely in the environment, to achieve delay-free, shadowless projection for tabletop workspaces without requiring computational compensation. To address spatial resolution degradation caused by subpixel misalignment among overlaid projections, we develop and validate an offline blur compensation method whose computation time remains independent of the number of projectors. Furthermore, we demonstrate that our shadowless PM plays a critical role in achieving a fundamental goal of PM: altering material properties without evoking projection-like impression. Specifically, we define this perceptual impression as ``sense of projection (SoP)'' and establish a PM design framework to minimize the SoP based on user studies.
Paper Structure (22 sections, 7 equations, 15 figures, 1 table)

This paper contains 22 sections, 7 equations, 15 figures, 1 table.

Table of Contents

  1. Introduction
  2. Related Work
  3. Shadowless Projection Mapping
  4. Blur Compensation in Projection Mapping
  5. Sense of Projection
  6. Our Contribution
  7. Synthetic Aperture Projector for Shadowless Projection Mapping
  8. Experiments
  9. System Configuration
  10. Evaluation of Shadow Removal Performance
  11. Planar Surface
  12. Non-Planar Surface
  13. Evaluation of Blur Compensation Method
  14. User Study
  15. Demonstrating the Suppression of the Sense of Projection
  16. ...and 7 more sections

Figures (15)

  • Figure 1: Proposed shadow removal principle by synthetic aperture projection. (Top) In a single-projector setup, shadows are cast when a user’s hand or other object approaches the projection surface and blocks the light path. (Bottom) In a synthetic aperture projection setup (25 projectors in this example), even if some projectors are occluded, light from the remaining projectors still reaches the surface, effectively reducing shadow formation.
  • Figure 2: The prototype synthetic aperture projection system using 25 projectors arranged in a 5$\times$5 grid. (a) A captured photograph of the ceiling-mounted projectors. (b) The system architecture that enables 2K video output to the 25 projectors.
  • Figure 3: Comparison of shadow removal performance between single-projector (left) and 25-projector (right) setups on the tabletop surface. (Top) The hand is positioned approximately 0.2 m above the surface. (Bottom) The hand touches four different locations on the surface.
  • Figure 4: Comparison of specular reflections between single-projector (left) and 25-projector (right) setups on the tabletop surface, from two different viewing directions.
  • Figure 5: Comparison of shadow removal performance between single-projector (top row) and 25-projector (bottom row) setups on the plaster bust surface. (1st column) Projections without the occluder. (2nd--4th columns) The finger touches different parts of the surface: the head (2nd column), the bust (3rd column), and the lower back of the head (4th column).
  • ...and 10 more figures