Fast separation of direct and global components of a scene using high frequency illumination

Abstract

a) Scene (b) Direct Component (c) Global Component Figure 1: (a) A scene lit by a single source of light.The scene includes a wide variety of physical phenomena that produce complex global illumination effects. We present several methods for separating the (b) direct and (c) global illumination components of the scene using high frequency illumination. In this example, the components were estimated by shifting a single checkerboard pattern 25 times to overcome the optical and resolution limits of the source (projector) and sensor (camera). The direct and global images have been brightness scaled by a factor of 1.25. In theory, the separation can be done using just 2 images. When the separation results are only needed at a resolution that is lower than those of the source and sensor, the separation can be done with a single image. AbstractWe present fast methods for separating the direct and global illumination components of a scene measured by a camera and illuminated by a light source. In theory, the separation can be done with just two images taken with a high frequency binary illumination pattern and its complement. In practice, a larger number of images are used to overcome the optical and resolution limitations of the camera and the source. The approach does not require the material properties of objects and media in the scene to be known. However, we require that the illumination frequency is high enough to adequately sample the global components received by scene points. We present separation results for scenes that include complex interreflections, subsurface scattering and volumetric scattering. Several variants of the separation approach are also described. When a sinusoidal illumination pattern is used with different phase shifts, the separation can be done using just three images. When the computed images are of lower resolution than the source and the camera, smoothness constraints are used to perform the separation using a single image. Finally, in the case of a static scene that is lit by a simple point source, such as the sun, a moving occluder and a video camera can be used to do the separation. We also show several simple examples of how novel images of a scene can be computed from the separation results.

A Dual Theory of Inverse and Forward Light Transport

“…This relates most closely to [Nayar et al 2006], who used a high-frequency illumination pattern and its complement. However, that method works only for a single image, where the entire scene is illuminated by the single light source or projector-not for the full light transport where the response for individual scene elements is computed, and where the incident illumination can come from many sources.…”

“…However, that method works only for a single image, where the entire scene is illuminated by the single light source or projector-not for the full light transport where the response for individual scene elements is computed, and where the incident illumination can come from many sources. On the other hand, we do first require acquisition of full light transport, unlike [Nayar et al 2006]. Moreover, we can separate the different bounces of global illumination, like [Seitz et al 2005], and can do so with much higher-resolution transport matrices at interactive rates.…”

Diffuse structured light

“…using high-frequency illumination [11]. In our experiments, we used 18 shifted high frequency binary stripe patterns.…”

“…(f) Ramp brightness function, (g) triangular function and (h) sinusoid used for depth estimation [3]. (i) High-frequency stripe pattern used for separation of direct and indirect illumination [11].…”

Ground-Truth Tracking Data Generation Using Rotating Real-World Objects

“…First of all, we calculate the direct and indirect intensity of the light, pixel by pixel for each image set. The full method is described in (Nayar et al, 2006). Then the minimum and maximum intensities are determined per pixel and the direct and indirect values are given by the equations as follows:…”