Physically Based Animation of sea Anemones in Real-Time

This paper presents a technique for modeling and animating fiberlike objects such as sea anemones tentacles in real-time. Each fiber is described by a generalized cylinder defined around an articulated skeleton. The dynamics of each individual fiber is controlled by a physically based simulation that updates the position of the skeleton’s frames over time. We take into account the forces generated by the surrounding fluid as well as a stiffness function describing the bending behavior of the fiber. High level control of the animation is achieved through the use of four types of singularities to describe the three-dimensional continuous velocity field representing the fluid. We thus animate hundreds of fibers by key-framing only a small number of singularities. We apply this algorithm on a seascape composed of many sea anemones. We also show that our algorithm is more general and can be applied to other types of objects composed of fibers such as seagrasse

A Method for the Symbolic Representation of Neurons

The field of neuroanatomy has progressed considerably in recent decades, thanks to the emergence of novel methods which provide new insights into the organization of the nervous system. These new methods have produced a wealth of data that needs to be analyzed, shifting the bottleneck from the acquisition to the analysis of data. In other disciplines, such as in many engineering areas, scientists and engineers are dealing with increasingly complex systems, using hierarchical decompositions, graphical models and simplified schematic diagrams for analysis and design processes. This approach makes it possible for users to simultaneously combine global system views and very detailed representations of specific areas of interest, by selecting appropriate representations for each of these views. In this way, users can concentrate on specific details while also maintaining a general system overview — a capability that is essential for understanding structure and function whenever complexity is an issue. Following this approach, this paper focuses on a graphical tool designed to help neuroanatomists to better understand and detect morphological characteristics of neuronal cells. The method presented here, based on a symbolic representation that can be tailored to enhance a particular range of features of a neuron or neuron set, has proven to be useful for highlighting particular geometries that may be hidden due to the complexity of the analysis tasks and the richness of neuronal morphologies. A software tool has been developed to generate graphical representations of neurons from 3D computer-aided reconstruction files

Generalization of the pedal concept in bidimensional spaces. Application to the limaçon of Pascal = Generalización del concepto de curva podal en espacios bidimensionales. Aplicación a la Limaçon de Pascal

The concept of a pedal curve is used in geometry as a generation method for a multitude of curves. The definition of a pedal curve is linked to the concept of minimal distance. However, an interesting distinction can be made for ?2. In this space, the pedal curve of another curve C is defined as the locus of the foot of the perpendicular from the pedal point P to the tangent to the curve. This allows the generalization of the definition of the pedal curve for any given angle that is not 90º. In this paper, we use the generalization of the pedal curve to describe a different method to generate a limaçon of Pascal, which can be seen as a singular case of the locus generation method and is not well described in the literature. Some additional properties that can be deduced from these definitions are also described. ----------RESUMEN---------- El concepto de curva podal está extendido en la geometría como un método generativo para multitud de curvas. La definición de curva podal está ligada al concepto de mínima distancia. Sin embargo, es posible hacer una interesante distinción en el espacios ℝ2. En este caso, la curva podal de otra curva C se define como el lugar geométrico de los pies de las perpendiculares desde un punto P a las tangentes a la curva. Esto permite generalizar la definición de curva podal a cualquier ángulo que no sea 90º. En este artículo utilizamos la generalización de curva podal para describir un método diferente de generación de la Limaçon de Pascal, que puede relacionarse como un caso particular del método de generación por lugares geométricos y que no se encuentra bien descrito en la literatura. También se describen algunas propiedades que pueden deducirse de estas definiciones