Incident Light Fields

Light is a fundamental natural phenomenon and is the primary carrier of perceptual information about our surroundings. the sun illuminates the earth during the day and during the night we can see its reflection in the moon. the stars in the sky are emitting enormous amounts of light of which a tiny fraction reaches the earth and human observers. Light is so important to us that we have even created artificial light sources such as lamps and fluorescent tubes that light up our homes in the evenings


Image based lighting, (IBL), is a computer graphics technique for creating photorealistic renderings of synthetic objects such that they can be placed into real world scenes. IBL has been widely recognized and is today used in commercial production pipelines. However, the current techniques only use illumination captured at a single point in space. This means that traditional IBL cannot capture or recreate effects such as cast shadows, shafts of light or other important spatial variations in the illumination. Such lighting effects are, in many cases, artistically created or are there to emphasize certain features, and are therefore a very important part of the visual appearance of a scene.This thesis and the included papers present methods that extend IBL to allow for capture and rendering with spatially varying illumination. This is accomplished by measuring the light field incident onto a region in space, called an Incident Light Field, (ILF), and using it as illumination in renderings. This requires the illumination to be captured at a large number of points in space instead of just one. The complexity of the capture methods and rendering algorithms are then significantly increased.The technique for measuring spatially varying illumination in real scenes is based on capture of High Dynamic Range, (HDR), image sequences. For efficient measurement, the image capture is performed at video frame rates. The captured illumination information in the image sequences is processed such that it can be used in computer graphics rendering. By extracting high intensity regions from the captured data and representing them separately, this thesis also describes a technique for increasing rendering efficiency and methods for editing the captured illumination, for example artificially moving or turning on and of individual light sources.


1 Introduction
1.1 Computer graphics
1.2 High dynamic range imaging
1.3 Image based lighting
1.4 Incident light fields
1.5 Application areas
1.6 Layout of the thesis
2 Notation and theoretical framework
2.1 Notation
2.2 Plenoptic function
2.3 Measuring the plenoptic function
2.4 Incident light field re-projection
2.5 Partial backprojection of the plenoptic function
2.6 Summary
3 Incident Light Fields
3.1 ILF capture
3.2 Rendering overview
3.3 Rendering with incident light fields
3.4 Rendering with light probe sequences
3.5 Illumination interaction and visualization
3.6 Illuminant extraction
3.7 Illuminant analysis and editing
4 Summary and Conclusion
5 Related Work
5.1 High dynamic range imaging
5.2 Image based lighting
5.3 Light field imaging
5.4 Summary

Author: Unger, Jonas

Source: Linkoping University

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