H. Andrade*, F. Ramos, Y. Kotsarenko

Tecnológico de Monterrey Cuernavaca, Morelos, México, *humberto.andrade@gmail.com.

ABSTRACT

Light and shadows caused by the interaction with objects are important features in computer graphics which are usually taken into account to achieve realistic images. In order to simulate them, some attempts have been carried out which are based on direct illumination classical approaches as shadow mapping and shadow volumes. However, classical approaches in their beginnings could not support semi-transparent objects, soft-shadows, light interactions inside objects and the possibility to update a scene based on previous information.

In this paper a novel shadow casting approach is proposed to solve the previously mentioned problem using an interactive cooperative multi agent system to provide a better understanding and easy customization of the rendered scenes; for instance, the scenes are represented with object agents that propagate rectilinear photon information through them causing several changes on photon properties such as wavelength, intensity, among others. This system uses a two-dimensional space represented by pixels.

Our multi-agent system (MAS) uses a blackboard architecture for storing and sharing data and the implicit invocation design pattern. The system was developed to calculate direct illumination in a two-dimensional space. In addition, the proposed system supports point light agents, opaque agents, semi-opaque agents and empty agents.

Keywords: shadows, ray-casting, multi agent system, blackboard.

RESUMEN

Luz y sombras causadas por la interacción con los objetos son características importantes en gráficas computacionales para lograr realismo en las imágenes. Para simularlas, se han hecho intentos en enfoques de iluminación directa como lo son shadow mapping y volumes. Sin embargo, éstas no pueden soportar objetos semitransparentes, sombras suaves, interacciones de la luz en el interior de los objetos y la posibilidad de actualizar una escena basada en información previa.

En éste trabajo se propone un novedoso enfoque de generación de sombras para resolver los problemas antes mencionados desarrollados bajo un enfoque de sistema multi-agente cooperativo para una mejor comprensión y una fácil personalización de escenas; como ejemplo, las escenas son representadas con agentes-objeto que propagan la información de los fotones de manera rectilínea entre ellos, causando varios cambios en las propiedades de los fotones como la frecuencia, intensidad, entre otros. Este sistema utiliza un espacio bidimensional representado por pixeles.

Nuestro sistema multi-agente (SMA) utiliza la arquitectura pizarrón (blackboard) para almacenar y compartir datos entre agentes y el patrón de diseño invocación implícita. El sistema fue desarrollado para calcular la iluminación local en un espacio discreto bidimensional. Adicionalmente, el sistema propuesto soporta agentes luz puntual, agente opaco, agente semi-opaco y agente vacío.

Se muestra una comparación entre los enfoques clásicos y la alternativa propuesta utilizando escenas con objetos opacos y semi-opacos. La alternativa propuesta en comparación con los enfoques clásicos permite sombras generadas por la luz al cruzar objetos semi-opacos. La luz es generada por uno o varios agentes luz puntual provocando sombras fuertes o suaves.

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