Abstract
One of the most-used rendering algorithms in Computer Graphics is the Ray-Tracing. The ''standard'' (Whited like) Ray-Tracing(1) is a good rendering algorithm but with a drawback: the time necessary to produce an image is too large (several hours of CPU time are necessary to make a good picture of a moderately sophisticated 3D scene) and the image is only ready to be observed at the end of processing. This kind of situation is difficult to accept in systems where interactivity is the first goal. ''Increasing Realism'' In Ray-Tracing tries to avoid the problem by supplying the user with a preview of the final image. This preview can be calculated in a considerably shorter time but permits that, with some margin of error, the user can imagine (even see, sometimes) some final effects. With more processing time the image quality continues improving without loss of previous results. The user can, at any time, interrupt the session if the image does not match what he wants. Simultaneously with the above idea, it is necessary to accelerate image production. Parallelism is then justified by the need of more processing power. The aim of this text is to describe the Interactive Ray-Tracing Algorithm implementation, using a parallel architecture based on Transputers. An overview of the architecture used is presented and the main parallel processes and related problems are discussed.

Abstract
In a distributed memory MIMD parallel machine, the efficient communication between processes/processors, through messages, is an important task to be handled by the programmer. Because the number of inter-processor connections is limited, the communication between any two processors is made by passing the messages through several other processors and then, a problem of messages routing appears. For dedicated systems, special architectures can be defined simplifying the problem but, if an environment constituting a basis for general applications development is desired, the problem is more serious due to the deadlock possibility. A general router, able to avoid the problem, becomes then a very important tool for software development in parallel architectures. We have been defining a development platform, based on a network of Transputers and written in OCCAM, for image synthesis applications. This paper reports our efforts in writing different versions of routers, based on two different strategies, and justifies the choice of an efficient one to integrate in the platform.

Abstract

Abstract
Cooperative environments to support Software Development (CSD) have as main goal to enable several users connected over network to work together in order to develop software. They have to solve problems such as: coherence maintenance of the software project through the distributed system by managing possible conflicts between local versions of each group member and promote the necessary mechanisms for the inter-group awareness and integrity. We introduce in this paper a distributed solution to support CSD by describing our own prototype: a Computer-Supported Cooperative Work (CSCW) architecture for software development. It enables a group of developers (2 to 4), possibly located at remote places and connected over network, to develop software together. A cooperative multimedia editing environment is available during the development cycle, enclosing mechanisms of computer-conferencing (text, audio and video communications).

Abstract

Abstract
Cooperative environments to support Software Development (CSD) have as main goal to enable several users connected over network to work together in order to develop software. They have to solve problems such as: coherence maintenance of the software project through the distributed system by managing possible conflicts between local versions of each group member and promote the necessary mechanisms for the inter-group awareness and integrity We introduce in this paper a distributed solution to support CSD by describing our own prototype: a Computer-Supported Cooperative Work (CSCW) architecture for software development. It enables a group of developers (2 to 4), possibly located at remote places and connected over network, to develop software together. A cooperative multimedia editing environment is available during the development cycle, enclosing mechanisms of computer-conferencing (text, audio and video communications).