Dan Englesson

Light source estimation using dual light probes

2011-10-18

Course: TNM089 - Imaging Technology

Abstract

Image based lighting captures the lighting in real environments very well such as outdoor scenes or scenes with distant light sources. Since the light is captured form a single position of a light probe in the world, the actual distance to the light sources are unknown and therefore important data for replicating the lighting conditions are lost. Only parallel shadows or relatively parallel shadows can be simulated with image based lighting, but by combining it with our method correct shadows can be calculated for the synthetic scene. The method triangulates point light-sources by using two light probes and one matted sphere used for estimating the world-positions of the three spheres. The method worked well for estimating light sources at distances up to 1.5 meters with an error of 10 percent of the distance. The error grows, as expected, with the distance so at 2 meters the error is about 35-40 percent of the distance, but with some more time and instead of estimating point light sources, area light sources can be estimated instead which will be less dependent on the estimated reflection vectors than point light sources and therefore the error could probably be reduced. For more details see the report below.

Course contents

This course will examine several films to explore the tricks of the trade. We will examine contemporary films, which use techniques that have been taught throughout the programme. The guest lecturers from industry will represent different stages of the SFX production ranging from research and development to compositing of final sequences. The learning outcomes of this course are as follows:

  • Conventional camera technology: optics, sensors and near-sensor signal processing like demosaicing.
  • Basic color imaging: multi-spectral and multi-channel imaging models and descriptions of illumination sources.
  • Light-matter interaction: BRDF capture, analysis and modeling.
  • Lightfield theory: Overview of techniques for multidimensional Lightfield capture and imaging.
  • Multi-image techniques: exposure bracketing, basic multi-view imaging and coded apertures.
  • Novel imaging techniques: Overview of experimental imaging techniques and some examples of imaging techniques in the non-visible wavelength range.

Full course information: TNM089 Imaging Technology

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