Germán Arroyo

Example-based stippling using a scale-dependent grayscale process

We present an example-based approach to synthesizing stipple illustrations for static 2D images that produces scale-dependent results appropriate for an intended spatial output size and resolution. We show how treating stippling as a grayscale process allows us to both produce on-screen output and to achieve stipple merging at medium tonal ranges. At the same time we can also produce images with high spatial and low color resolution for print reproduction. In addition, we discuss how to incorporate high-level illustration considerations into the stippling process based on discussions with and observations of a stipple artist. The implementation of the technique is based on a fast method for distributing dots using halftoning and can be used to create stipple images interactively.

Scale-dependent and example-based grayscale stippling

We present an example-based approach to synthesizing stipple illustrations for static 2D images that produces scale-dependent results appropriate for an intended spatial output size and resolution. We show how treating stippling as a grayscale process allows us to both produce on-screen output and to achieve stipple merging at medium tonal ranges. At the same time we can also produce images with high spatial and low color resolution for print reproduction. In addition, we discuss how to incorporate high-level illustration considerations into the stippling process based on discussions with and observations of a stipple artist. Also, certain features such as edges can be extracted and used to control the placement of dots to improve the result. The implementation of the technique is based on a fast method for distributing dots using halftoning and can be used to create stipple images interactively. We describe both a GPU implementation of the basic algorithm that creates stipple images in real-time for large images and an extended CPU method that allows a finer control of the output at interactive rates.

Scale-Dependent and Example-Based Stippling

We present an example-based approach to synthesizing stipple illustrations for static 2D images that produces scale-dependent results appropriate for an intended spatial output size and resolution. We show how treating stippling as a grayscale process allows us to both produce on-screen output and to achieve stipple merging at medium tonal ranges. At the same time we can also produce images with high spatial and low color resolution for print reproduction. In addition, we discuss how to incorporate high-level illustration considerations into the stippling process based on discussions with and observations of a stipple artist. Also, certain features such as edges can be extracted and used to control the placement of dots to improve the result. The implementation of the technique is based on a fast method for distributing dots using halftoning and can be used to create stipple images interactively. We describe both a GPU implementation of the basic algorithm that creates stipple images in real-time for large images and an extended CPU method that allows a finer control of the output at interactive rates.

Extended papers from NPAR 2010: Scale-dependent and example-based grayscale stippling

We present an example-based approach to synthesizing stipple illustrations for static 2D images that produces scale-dependent results appropriate for an intended spatial output size and resolution. We show how treating stippling as a grayscale process allows us to both produce on-screen output and to achieve stipple merging at medium tonal ranges. At the same time we can also produce images with high spatial and low color resolution for print reproduction. In addition, we discuss how to incorporate high-level illustration considerations into the stippling process based on discussions with and observations of a stipple artist. Also, certain features such as edges can be extracted and used to control the placement of dots to improve the result. The implementation of the technique is based on a fast method for distributing dots using halftoning and can be used to create stipple images interactively. We describe both a GPU implementation of the basic algorithm that creates stipple images in real-time for large images and an extended CPU method that allows a finer control of the output at interactive rates.

SP-ChainMail: a GPU-based sparse parallel ChainMail algorithm for deforming medical volumes

ChainMail algorithm is a physically based deformation algorithm that has been successfully used in virtual surgery simulators, where time is a critical factor. In this paper, we present a parallel algorithm, based on ChainMail, and its efficient implementation that reduces the time required to compute deformations over large medical 3D datasets by means of modern GPU capabilities. We also present a 3D blocking scheme that reduces the amount of unnecessary processing threads. For this purpose, this paper describes a new parallel boolean reduction scheme, used to efficiently decide which blocks are computed. Finally, through an extensive analysis, we show the performance improvement achieved by our implementation of the proposed algorithm and the use of the proposed blocking scheme, due to the high spatial and temporal locality of our approach.

Using a Cultural Heritage Information System for the documentation of the restoration process

Conventional information systems are frequently used to document Cultural Heritage sites. These systems are adequate for some specific purposes as they can store and retrieve a large amount of heterogeneous documents. Nevertheless, this is not enough for research and conservation purposes; researchers need to be able to find out relations between data. These relations are mostly spatial, and can be established by meaning of a 3D representation of the artifact. In order to achieve this, a new kind of information system is proposed, for which the 3D representation of the object is used as a blackboard, where all the data is represented. This paper describes the use of CHISel, a documentation tool that is designed as a GIS-like software for 3D cultural heritage, implementing the concept of a Cultural Heritage Information System (CHIS), and its application to document and analyze the restoration process of sculptures.

A stochastic approach to simulate artists behaviour for automatic felt-tipped stippling

Nowadays, non-photorealistic rendering is an area in computer graphics that tries to simulate what artists do and the tools they use. Stippling illustrations with felt-tipped colour pen is not a commonly used technique by artists due to its complexity. In this paper we present a new method to simulate stippling illustrations with felt-tipped colour pen from a photograph or an image. This method infers a probability function with an expert system from some rules given by the artist and then simulates the behaviour of the artist when placing the dots on the illustration by means of a stochastic algorithm.

Silhouette detection in volumetric models based on a non-photorealistic illumination system

A basic step for many illustration techniques is the extraction of silhouettes and shape lines, in order to enhance the object shape visible to the observer. This paper presents a new and very fast method to obtain silhouettes and shape lines in non-photorealistic volume rendering processes, based on ray-tracing using an octree for optimization. This method consists of extracting contours based on image buffers acquired during the calculation of intersections in ray-tracing process with the model. These image buffers are then combined to produce silhouettes and shape lines from the model. A substantial improvement with regard to other silhouette extraction methods in volumes is that this method does not require the user to define thresholds; furthermore, it is not based on the z-buffer and thus does not depend on the precision of the latter. Neither the camera position nor the direction affect the performance of the algorithm. Finally, the algorithm detects silhouettes for objects which are inside other objects that are distinguished only by their hue.