The construction of polygonal meshes remains a complex task in Computer Graphics, taking tens of thousands of individual operations over several hours of modeling time. The complexity of modeling in terms of number of operations and time makes it difficult for artists to understand all details of how meshes are constructed. We present MeshFlow , an interactive system for visualizing mesh construction sequences. MeshFlow hierarchically clusters mesh editing operations to provide viewers with an overview of the model construction while still allowing them to view more details on demand. We base our clustering on an analysis of the frequency of repeated operations and implement it using substituting regular expressions. By filtering operations based on either their type or which vertices they affect, MeshFlow also ensures that viewers can interactively focus on the relevant parts of the modeling process. Automatically generated graphical annotations visualize the clustered operations. We have tested MeshFlow by visualizing five mesh sequences each taking a few hours to model, and we found it to work well for all. We have also evaluated MeshFlow with a case study using modeling students. We conclude that our system provides useful visualizations that are found to be more helpful than video or document-form instructions in understanding mesh construction.

Abstract In computer cinematography, artists routinely use non‐physical lighting models to achieve desired appearances. This paper presentsBendyLights, a non‐physical lighting model where light travels nonlinearly along splines, allowing artists to control light direction and shadow position at different points in the scene independently. Since the light deformation is smoothly defined at all world‐space positions, the resulting non‐physical lighting effects remain spatially consistent, avoiding the frequent incongruences of many non‐physical models.BendyLightsare controlled simply by reshaping splines, using familiar interfaces, and require very few parameters.BendyLightcontrol points can be keyframed to support animated lighting effects. We demonstrateBendyLightsboth in a realtime rendering system for editing and a production renderer for final rendering, where we show thatBendyLightscan also be used with global illumination.

Material design is the process by which artists specify the reflectance properties of a surface, such as its diffuse color and specular roughness. We present a user study to evaluate the relative benefits of different material design interfaces, focusing on novice users since they stand to gain the most from intuitive interfaces. Specifically, we investigate the editing of the parameters of analytic bidirectional distribution functions (BRDFs) using three interface paradigms: physical sliders by which users set the parameters of analytic BRDF models, such as diffuse albedo and specular roughness; perceptual sliders by which users set perceptually-inspired parameters, such as diffuse luminance and gloss contrast; and image navigation by which material variations are displayed in arrays of image thumbnails and users make edits by selecting them. We investigate two design tasks: precise adjustment and artistic exploration. We collect objective and subjective data, finding that subjects can perform equally well with physical and perceptual sliders as long as the interface responds interactively. Image navigation performs worse than the other interfaces on precise adjustment tasks, but excels at aiding in artistic exploration. We find that given enough time, novices can perform relatively complex material editing tasks with little training, and most novices work similarly to one another.

Lighting design is a complex but fundamental task in computer cinematography, involving the adjustment of light parameters to define final scene appearance. Many user interfaces have been proposed to simplify lighting design. They can be generally categorized in three paradigms: direct light parameter manipulation, indirect light feature manipulation (e.g., shadow dragging), and goal-based optimization of lighting through painting. To this date, no formal evaluation of the relative effectiveness of these paradigms has been performed. In this paper, we present a first step toward evaluating the benefits of these three paradigms in the form of a user study with a focus on novice users. 20 subjects participated in the experiment by performing various trials on simple scenes with up to 8 point lights, designed to test two lighting tasks: precise adjustment of lighting and the artistic exploration of lighting configurations. We collected objective and subjective data and found that subjects can light well with direct and indirect interfaces, preferring the latter. Paint-based goal specification was found to be significantly worse than the other paradigms, especially since users tend to sketch rather than accurately paint goal images, an input that painting algorithms were not designed for. We also found that given enough time, novices can perform relatively complex lighting tasks, unhindered by geometry or lighting complexity. Finally, we believe that our study will impact the design of future lighting interfaces and it will serve as the basis for designing additional experiments to reach a comprehensive evaluation of lighting interfaces.