We design and evaluate Mindful Scroll, a mobile application for mindfulness that encourages a slow and deliberate approach to colouring. The app renders an infinite scroll of generated geometric tilings that reveal pseudo-random colour palettes and fill effects when coloured using a finger or pen. A five-day study (N=28) evaluated the efficacy of the app in reducing anxiety and enhancing mindfulness. The results indicate that the app is capable of promoting a greater sense of mindfulness over time and produced similar results across several measures compared to traditional structured colouring and existing mindfulness-based mobile applications. All participants expressed a desire to use the app again, with a majority stating they felt more mindful after the study.

In art, hatching means drawing patterns of roughly parallel lines. Even with skill and time, an artist can find these patterns difficult to create and edit. Our new artistic primitive—the hatching shape—facilitates hatching for an artist drawing from imagination. A hatching shape comprises a mask and three fields: width, spacing, and direction. Streamline advection uses these fields to create hatching marks. A hatching shape also contains barrier curves: deliberate discontinuities useful for drawing complex forms. We explain several operations on hatching shapes, such as the multi-dir operation, an easy way to depict 3D form using a hatching shape’s direction field. We also explain the modifications to streamline advection necessary to produce hatching marks from a hatching shape.

Gesture drawing is a type of fluid, fast sketch with loose and roughly drawn lines which capture the motion and feeling of a subject. While style transfer methods, which are able to learn a style from an input image and apply it to a secondary image, can reproduce many styles, they are currently unable to produce the flowing strokes of gesture drawings. In this paper, we present a method to produce gesture drawings, which roughly depict objects or scenes with loose, dancing contours, and frantic textures. Our method adapts stroke-based painterly rendering algorithms to produce long, curved strokes by following the gradient field. A rough, overdrawn appearance is created through progressive refinement.Additionally, we produce rough hatch strokes by altering stroke direction. These add optional shading to the gesture drawings. The wealth parameters that provide users the ability to adjust the output style from short, rapid strokes to long, fluid strokes, from swirling to straight lines. Potential stylistic outputs also include pen-and-ink and coloured pencil. We present several generated gesture drawings and discuss how our method can be applied to video. Our stroke-based rendering algorithm produces convincing gesture drawings with numerous controllable parameters permitting the creation of a variety of styles.

We present a method to fill a container shape with deformable instances of geometric elements selected from a library, creating a 2D artistic composition called an element packing. Each element is represented as a mass-spring system, allowing it to deform to achieve a better fit with its neighbours and the container. We start with an initial placement of small elements and gradually transform them using a physics simulation that trades off between the evenness of the packing and the deformations of the individual elements. Unlike previous work, elements can be given preferred orientations, and we can use shape matching to control the initial placement of elements in tight convex corners. We also explore the creation of tileable packings, and validate our approach using statistical measurements of the distributions of positive and negative space in packings. Our method produces compositions in which the negative space between elements is approximately uniform in width, similar to real-world examples created by artists.

We present AnimationPak, a technique to create animated packings by arranging animated two-dimensional elements inside a static container. We represent animated elements in a three-dimensional spacetime domain, and view the animated packing problem as a three-dimensional packing in that domain. Every element is represented as a discretized spacetime mesh. In a physical simulation, meshes grow and repel each other, consuming the negative space in the container. The final animation frames are cross sections of the three-dimensional packing at a sequence of time values. The simulation trades off between the evenness of the negative space in the container, the temporal coherence of the animation, and the deformations of the elements. Elements can be guided around the container and the entire animation can be closed into a loop.

A common workflow for modern comic artists is to create an inked line drawing using traditional tools. Then the drawing is scanned as black and white line art and coloured digitally using an application such as Photoshop [Abel and Madden 2012]. The first step of digital colouring, called flatting, assigns symbolic colours to each region in an image which a colourist can use to apply final colours and other effects. There is little direct support for flatting in software, which results in a manual, labour intensive process for artists. Further, an object in a drawing may be split into multiple regions due to occlusions, requiring an artist to assign the same colour to each region of the object. This work describes a quantitative framework that allows occlusion cues, derived from vision research, to be computed and compared with each other. This framework is used to simplify comic flatting, allowing an artist to flat multiple regions in a single click. Simple gestural tools that can be used to add additional guidance to occlusion processing are also provided.

Vector graphics representations of images are resolution independent. Direct use of vector images for real-time texture mapping would be desirable to avoid sampling artifacts such as blurring common with raster images. Scalable Vector Graphics (SVG) files are typical of vector graphics image representations. Such representations composite images from layers of paths and strokes defined with lines, elliptical arcs, and quadratic and cubic parametric splines.High-quality texture mapping requires both random access and anisotropic antialiasing. For vector images, these goals can be achieved by computing the distance to the closest primitives from a sample point and then mapping this distance through a soft threshold function. Representing transparency masks in this way is especially useful, since vector mattes can be used to render complex curvilinear geometry as textures on simple geometric primitives.Unfortunately, computing the exact minimum distance to the parametric curves used in vector images is difficult. Previous work has used approximations, but an accurate minimum distance is desirable in order to enable wide strokes and special effects such as embossing. In this paper, a simple algorithm is presented that can efficiently and accurately compute the minimum distance to a parametric curve when the sample point is within its radius of curvature and the curve can be segmented into monotonic regions. This technique can be used in a GPU shader to render antialiased vector images exactly as defined by SVG files.

There are many algorithms in non-photorealistic rendering for representing an image as a composition of small objects. In this paper, we focus on the specific case where the objects to be assembled into a composition are letters rather than images or abstract geometric forms. We develop a solution to the "calligraphic packing" problem based on dividing up a target region into pieces and warping a letter into each piece. We define an energy function that chooses a warp that best represents the original letter. We discuss variations in rendering style and show results produced by our system.

The craft of papercutting is part of the folk art traditions of cultures all over the world. From the point of view of computer graphics, papercutting can be seen as a method of composing bi-level images under a set of geometric connectivity constraints. In this paper, we present a technique for composing digital paper-cut designs. The elements of a design may be images, which are processed via a multilayer thresholding operation, or they may be procedurallygenerated arrangements of shapes. Elements are composed using a set of boolean operators that preserve connectivity. The resulting designs are well suited to being cut by a new generation of inexpensive computer peripherals.

We present a set of graphical and combinatorial algorithms for designing mazes based on images. The designer traces regions of interest in an image and annotates the regions with style parameters. They can optionally specify a solution path, which provides a rough guide for laying out the maze's actual solution. The system uses novel extensions to well-known maze construction algorithms to build mazes that approximate the tone of the source image, express the desired style in each region, and conform to the user's solution path.

We introduce symSpline: a symmetric, dual-mouse technique for the manipulation of spline curves. In symSpline, two cursors control the positions of the ends of the tangent to an edit point. By moving the tangent with both mice, the tangent and the edit point can be translated while the curvature of the spline is adjusted simultaneously, according to the length and angle of the tangent. We compare the symSpline technique to two asymmetric dual-mouse spline manipulation techniques and to a standard single-mouse technique. In a spline matching experiment, symSpline outperformed the two asymmetric dual-mouse techniques and all three dual-mouse techniques proved to be faster than the single-mouse technique. Additionally, symSpline was the technique most preferred by test participants.

We present a vector graphics representation suitable for real-time rendering on GPUs. Our representation can be used in place of a texture map, and renders precise antialiased edges at any magnification. A combination of texture data and procedural computation is used to evaluate an exact signed distance to a contour and its gradient. An optimized uniform grid accelerator is created using Voronoi analysis and redundancy elimination, so only the distances to a small constant number of features need be computed at every access. Contours and sharp features can be exactly reconstructed using a constant amount of computation per pixel. Our representation supports inexpensive high-quality anisotropic antialiasing as well as special effects such as outlining (with both rounded and sharp miters) and embossing.We have applied our representation to the important application of glyph rendering. Variations in glyph complexity are handled by storing different glyphs at different grid resolutions. Large blocks of glyphs can be rendered efficiently with a single indirection through an index texture.

We present an evaluation of three mouse-based techniques for aligning digital images. We investigate the physical image alignment task and discuss the implications for interacting with virtual images. In a formal evaluation we show that a symmetric bimanual technique outperforms an asymmetric bimanual technique which in turn outperforms a unimanual technique. We show that even after mode switching times are removed, the symmetric technique outperforms the single mouse technique. Subjects also exhibited more parallel interaction using the symmetric technique than when using the asymmetric technique.

We present Najm , a set of tools built on the axioms of absolute geometry for exploring the design space of Islamic star patterns. Our approach makes use of a novel family of tilings, called "inflation tilings," which are particularly well suited as guides for creating star patterns. We describe a method for creating a parameterized set of motifs that can be used to fill the many regular polygons that comprise these tilings, as well as an algorithm to infer geometry for any irregular polygons that remain. Erasing the underlying tiling and joining together the inferred motifs produces the star patterns. By choice, Najm is build upon the subset of geometry that makes no assumption about the behavior of parallel lines. As a consequence, star patterns created by Najm can be designed equally well to fit the Euclidean plane, the hyperbolic plane, or the surface of a sphere.

This paper introduces and presents a solution to the “Escherization” problem: given a closed figure in the plane, find a new closed figure that is similar to the original and tiles the plane. Our solution works by using a simulated annealer to optimize over a parameterization of the “isohedral” tilings, a class of tilings that us flexible enough to encompass nearly all of Escher's own tilings, and yet simple enough to be encoded and explored by a computer. We also describe a representation for isohedral tilings that allows for highly interactive viewing and rendering. We demonstrate the use of these tools—along with several additional techniques for adding decorations to tilings—with a variety of original ornamental designs.