An algorithm for generating shadows with an umbra and penumbra due to distributed light sources is presented. The method used is based on the inclusion of the shadow volumes in the object data processed by a depth-buffer visible surface computation. The standard depth-buffer data structure is modified to allow the handling of shadows with a depth-buffer hidden surface algorithm. The algorithm i...

Shadows serve as e ective cues for a user to recognize spatial relations among objects in 3D space. However simple shadows typically used in 3D interfaces are often insu cient for the purpose, and rendering of shadows with real penumbra are not only too costly for interactive interfaces, but also do not enhance their capabilities as spatial cues. Our proposal, layered penumbra is a new interact...

Abstract In addition to the Evershed flow directed from umbra toward outer boundary of a sunspot, under special circumstances counter (CEF) in opposite direction also occurs. We aim characterize proper motions and evolution three CEFs observed by Solar Optical Telescope on board Japanese Hinode spacecraft Helioseismic Magnetic Imager Dynamics Observatory. use state-of-the-art inversions radiati...

We analyse a sunspot simulation in an effort to understand the origin of convective instabilities giving rise penumbral and umbral distinct regimes. applied criterion from Gough \& Tayler (1966), accounting for stabilising effect vertical magnetic field investigate MURaM simulation. find: (1) highly unstable shallow layer right beneath surface extending all over box which convection is triggere...

We present an exact method to compute the boundaries between umbra, penumbra and full-light regions cast on a plane by a set of disjoint convex polyhedra, some of which are light sources. This method builds on a recent characterization of topological visual event surfaces presented in a companion paper.

Context. Umbral Dots (UDs) are thought to be manifestations of magnetoconvection in sunspot umbrae. Recent advances in their theoretical description point to the need for a thorough study of their properties and evolution based on data with the highest currently achievable resolution. Aims. Our UD analysis aims to provide parameters such as lifetimes, diameters, horizontal velocities, and peak ...

Context. Substructures – dark lanes and tails – of umbral dots (UDs) were predicted by numerical simulations of magnetoconvection and have been detected later in some observations. Aims. To provide constraints for realistic theoretical models of sunspot umbrae, we describe the observed properties and evolutionary characteristics of UDs (including their substructure) and of other umbral structur...