光照一致性是增强现实中实现虚实融合的重要方面,实时地估计出户外场景中的光照方向,对实现户外场景光照一致性和增强真实感具有重要意义.针对光照方向估计问题,首先归纳了户外场景光照方向估计的特点,把现有的光照方向估计方法分为借助光测球等特殊标定物的估算方法、立体视觉法和人工智能法3类方法.然后总结了各类方法的基本原理和有代表性的研究工作,并且比较了各类方法的优缺点和适用范围.最后,根据实际应用中存在的问题和挑战,展望了户外增强现实系统光照方向估计的研究方向.%Illumination consistency plays an important role in merging virtual objects into real scenes for augmented reality. Real-time illumination direction estimation for outdoor scenes is important for both illumination consistency and high realism of augmented reality. Aiming at problems of illumination direction estimation, characteristics of illumination direction estimation for outdoor scenes are generalized, and the taxonomy of illumination direction estimation methods is presented. Existing illumination direction estimation methods consist of light probe sphere based method, stereo vision based method and artificial intelligence based method. Relevant fundamental principles and typical algorithms are concluded, and their advantages and disadvantages are compared in detail. Finally, according to existing problems and challenges in actual applications, future research trends of illumination direction estimation for outdoor augmented reality systems are foreseen.
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