Computational Light Painting and Kinetic Photography

Abstract

We present a computational framework for creating swept volume light painting and kinetic photography. Unlike conventional light painting technique using hand-held point light source or LED arrays, we move a flat-panel display with robot in a curved path. The display shows real-time rendered contours of a 3D object being sliced by the display plane along the path. All light contours are captured in a long exposure and constitute the virtual 3D object augmented in the real space. To ensure geometric accuracy, we use hand-eye calibration method to precisely obtain the transformation between the display and the robot. A path generation algorithm is developed to automatically yield the robot path that can best accommodate the 3D shape of the target model. To further avoid shape distortion due to asynchronization between the display's pose and the image content, we propose a real-time slicing method for arbitrary slicing direction. By organizing the triangular mesh into Octree data structure, the approach can significantly reduce the computational time and improve the performance of real-time rendering. We study the optimal tree level for different range of triangle numbers so as to attain competitive computational time.Texture mapping is also implemented to produce colored light painting. We extend our methodologies to computational kinetic photography, which is dual to light painting. Instead of keeping the camera stationary, we move the camera with robot and capture long exposures of a stationary display showing light contours. We transform the display path for light painting to the camera path for kinetic photography. A variety of 3D models are used to verify that the proposed techniques can produce stunning long exposures with high-fidelity volumetric imagery. The techniques have great potential for innovative applications including animation, visible light communication, invisible information visualization and creative art.