Artistic silhouettes

Northrup, J. D.; Markosian, Lee

doi:10.1145/340916.340920

Cited by 133 publications

(15 citation statements)

References 14 publications

(14 reference statements)

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“…An alternative solution proposed by Northrup and Markosian (2000) is based on an item buffer, which had previously been used to accelerate ray-tracing (Weghorst et al, 1984). The idea is to render each line into an off-screen buffer (e.g., a Framebuffer Object in OpenGL) with a thickness of one pixel and a unique color (ID).…”

Section: Item Buffermentioning

confidence: 99%

Line Drawings from 3D Models: A Tutorial

Bénard¹,

Hertzmann²

2019

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This tutorial describes the geometry and algorithms for generating line drawings from 3D models, focusing on occluding contours.The geometry of occluding contours on meshes and on smooth surfaces is described in detail, together with algorithms for extracting contours, computing their visibility, and creating stylized renderings and animations. Exact methods and hardware-accelerated fast methods are both described, and the trade-offs between different methods are discussed. The tutorial brings together and organizes material that, at present, is scattered throughout the literature. It also includes some novel explanations, and implementation tips.We believe that these topics ought to be known by anyone interested in understanding the curves in visual representational art. It is one where computer graphics can make a unique contribution. Arguably, the algorithmic simulation of line drawing is a crucial step in understanding visual art. Occluding contoursThis tutorial focuses on the curves known as occluding contours or, simply contours. In some computer graphics research, these have been called silhouettes, though the silhouettes are technically a separate set of curves, as we will describe below.The occluding contours of a simple 3D object are shown in Figure 1.1. As a first definition, suppose we have a 3D object that we wish to render from a specific viewpoint. The occluding contours are surface curves that separate visible parts from invisible parts. By rendering the visible portions of these 3D curves together with the object, we get a basic line drawing (Figure 1.1b).There are many different contour detection and rendering algorithms, and some significant tradeoffs between them. The most important tradeoff is between simple algorithms that produce approximate results, and more complex algorithms that give more precision, control, and stylization capabilities. Just rendering reasonable-looking contours as solid black lines is very straightforward for a graphics programmer. These most basic algorithms can be implemented in a few additional lines of code in an existing renderer, and have been implemented in many real-time applications, including many popular video games (one of the earliest was Jet Set Radio in 2000). However, if we wish to stylize the curves, for example, by rendering the curves with sketchy or calligraphic strokes (Figure 1.1d), things become more difficult. With a bit of perseverance, renderings with distinctive and lovely styles can be created. At times, these renderings may still contain topological artifacts that are not suitable for very high-end production. High-quality algorithms that remove these artifacts are more complex; in the extreme, no provably-correct algorithm exists for this problem. However, there are a number of partial solutions that are good enough to be used in many circumstances, and we discuss in detail the issues involved.Note that, formally, the occluding contour and occluding contour generator are separate curves in 2D and 3D. However, we will frequently use the te...

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Section: Item Buffermentioning

confidence: 99%

Line Drawings from 3D Models: A Tutorial

Bénard¹,

Hertzmann²

2019

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“…The chalk sticks themselves are simulated using an 1D alpha texture. Using the points of the strokes, along with width and pressure values, a mesh is created representing the geometry of the strokes [24]. Using the paper height map and the stroke's pressure values, the mesh is coloured using the colour of the chalk stick.…”

Section: Simulation Of Highly Rendered Stylesmentioning

confidence: 99%

Highly Stylised Drawn Animation

Fiore

Reeth

Patterson

et al. 2006

Advances in Computer Graphics

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Abstract. In this paper we argue for our NPAR system as an effective 2D alternative to most of NPR research that is focused on frame coherent stylised rendering of 3D models. Our approach gives a highly stylised look to images without the support of 3D models, and yet they still behave as though animated by drawing, which they are. First, a stylised brush tool is used to freely draw extreme poses of characters. Each character is built up of 2D drawn brush strokes which are manually grouped into layers. Each layer is assigned its place in a drawing hierarchy -Hierarchical Display Model (HDM). Next, multiple HDMs are created for the same character, each corresponding to a specific view. A collection of HDMs essentially reintroduces some correspondence information to the 2D drawings needed for in-betweening and, in effect, eliminates the need for a true 3D model. Once the models are composed, the animation phase can start. The animator first defines keyframes by specifying extreme poses in time. Next, brush stroke trajectories defined by the HDMs of the keyframes are inbetweened automatically across intermediary frames. Finally, each HDM of each generated in-between frame is traversed and all elements are drawn one on another from back to front. Regarding stylisation, we focus on techniques that realise highly rendered styles which are particularly difficult to animate by traditional means including the 'airbrushed', scraperboard, watercolour, Gouache, 'ink-wash', and the 'crayon' style. We believe our system offers a new fresh perspective on computer aided animation production and associated tools.

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“…There have been several methods that use traditional graphics hardware to achieve real time silhouettes [Elber 1999;Gooch et al 1999;Hertzmann and Zorin 2000;Markosian et al 1997;Northrup and Markosian 2000;Raskar and Cohen 1999] and artistic silhouettes . However, rendering the texture mapped model achieves the closure effect without an explicit computation of silhouettes.…”

Section: Introductionmentioning

confidence: 99%

Hardware accelerated real time charcoal rendering

Majumder

Gopi

2002

Proceedings of the 2nd International Symposium on Non-Photorealistic Animation and Rendering

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In this paper, we present simple rendering techniques implemented using traditional graphics hardware to achieve the effects of charcoal drawing. The effects include characteristics of charcoal drawings like broad grainy strokes and smooth tonal variations that are achieved by smudging the charcoal by hand. Further, we also generate the closure effect that is used by artists at times to avoid hard silhouette edges. All these effects are achieved using contrast enhancement operators on textures and/or colors of the 3D model.Our contribution lies in unifying the methods to achieve these effects under the common framework of contrast enhancement operators. Further, since the effects have been implemented using traditional graphics hardware, a single rendering pass is sufficient to create different effects. Hence, we can render highly complex models with large number of triangles at interactive rates. Thus, our method is especially suited for applications like scientific visualization and preliminary sketches/animations.

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Artistic silhouettes

Cited by 133 publications

References 14 publications

Line Drawings from 3D Models: A Tutorial

Line Drawings from 3D Models: A Tutorial

Highly Stylised Drawn Animation

Hardware accelerated real time charcoal rendering

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