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We solve the light transport problem by introducing a novel unbiased Monte Carlo algorithm called replica exchange light transport, inspired by the replica exchange Monte Carlo method in the fields of computational physics and statistical information processing. The replica exchange Monte Carlo method is a sampling technique whose operation resembles simulated annealing in optimization algorithms using a set of sampling distributions. We apply it to the solution of light transport integration by extending the probability density function of an integrand of the integration to a set of distributions. That set of distributions is composed of combinations of the path densities of different path generation types: uniform distributions in the integral domain, explicit and implicit paths in light (particle/photon) tracing, indirect paths in bidirectional path tracing, explicit and implicit paths in path tracing, and implicit caustics paths seen through specular surfaces including the delta function in path tracing. The replicaexchange light transport algorithm generates a sequence of path samples from each distribution and samples the simultaneous distribution of those distributions as a stationary distribution by using the Markov chain MonteCarlo method. Then the algorithm combines the obtained path samples from each distribution using multiple importance sampling. We compare the images generated with our algorithm to those generated with bidirectional path tracing and Metropolis light transport based on the primary sample space. Our proposing algorithm has better convergence property than bidirectional path tracing and the Metropolis light transport, and it is easy to implement by extending the Metropolis light transport.

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This paper describes a new teleconference terminal constructed on the X.25 protocol for high speed packet switching over 1.5Mb /s subscriber lines. To develop a high performance teleconferencing system, the terminal incorporates three transmission techniques: variable bit rate coding and packet priority assignment of video signals, combining left and right audio channels and assignment of audio packet priority, and under severe traffic congestion the dropping of video data packets if there are no low priority audio packets that can be dropped. If a sending terminal detects traffic congestion severe enough to prevent transmission of all packets, the least significant audio packets are dropped until audio signal rate falls to 32kb /s. Next, video data packets are dropped if the traffic congestion is very severe. Sound localization, important in conferences, is maintained even under heavy traffic congestion. The influence of packet loss on picture and audio quality is described and decoded pictures suffering various packet losses are investigated.With this newly developed teleconferencing terminal, consistent and high quality multi -media services can be assured. 1.INTRODUCTIONThe use of teleconferencing systems has been spreading rapidly in many countries to provide effective human -to -human communications. The systems use audio, audio -graphic, and video media.1 Video signals are necessary to create a natural visual and audio space for attendees that is superior to that created by traditional conferencing techniques. This space must have two characteristics for the adequate presentation of human motion and behaviour: picture quality of the highest possible level and sound localization. Picture quality depends on video bit rate which fluctuates following recorded motion due to the use of a differential signal between video frames, called interframe prediction. There is a relationship between signal burstiness and packet transmission rate. Thus packet transmission is an important consideration for picture quality. Sound localization is effective when some attendees are not currently displayed in order to effectively control camera movement. Stereophonic transmission is the best technique to realize this localization. This paper describes a new conference terminal which incorporates three transmission techniques: variable bitrate coding and packet priority assignment of video signals, combining left and right audio channels and assignment of audio packet priority, and under severe traffic congestion the dropping of video data packets if there are no low priority audio packets that can be dropped. Reasons for connecting the terminal to a High -speed highthroughput packet switching system2 are described in Section 2. The system configuration of the new terminal and the transmission techniques to control packet quantity are proposed in Section 3 and 4 respectively. Finally, the current service applications and future expansion to Ethernet and ATM networks are discussed in Section 5. ABSTRACT This paper describes a new ...