Tom Van Laerhoven

Real-time simulation of watery paint

Existing work on applications for thin watery paint is mostly focused on automatic generation of painterly‐style images from input images, ignoring the fact that painting is a process that intuitively should be interactive. Efforts to create real‐time interactive systems are limited to a single paint medium and results often suffer from a trade‐off between real‐timeness and simulation complexity. We report on the design of a new system that allows the real‐time, interactive creation of images with thin watery paint. We mainly target the simulation of watercolor, but the system is also capable of simulating gouache and Oriental black ink. The motion of paint is governed by both physically based and heuristic rules in a layered canvas design. A final image is rendered by optically composing the layers using the Kubelka–Munk diffuse reflectance model. All algorithms that participate in the dynamics phase and the rendering phase of the simulation are implemented on graphics hardware. Images made with the system contain the typical effects that can be recognized in images produced with real thin paint, like the dark‐edge effect, watercolor glazing, wet‐on‐wet painting and the use of different pigment types. Copyright

FluidPaint: an interactive digital painting system using real wet brushes

This paper presents FluidPaint, a novel digital paint system using real wet brushes. A new interactive canvas, accurately registering brush footprints and paint strokes in high precision has been developed. It is based on the real-time imaging of brushes and other painting instruments as well as the real-time co-located rendering of the painting results. This new painting user interface enhances the user experience and the artists expressiveness. User tests demonstrate the intuitive nature of FluidPaint, naturally integrating interface elements of traditional painting in a digital paint system.

From dust till drawn: A real-time bidirectional pastel simulation

We present a system for drawing pastel media in real-time as an effective alternative to most existing digital solutions that basically allow for drawing arbitrary strokes in a particular style. Our approach is focused on the simulation of the natural material itself and on its interaction with the drawing surface and the drawing tool.Upon free-form drawing, a bidirectional transfer of pigment takes place. In one direction, the paper surface is dusted with new pigment particles broken off the tip (i.e., the end of the drawing tool). A large part of these particles will be deposited or blended together with previously deposited ones whereas the remainder does not contribute to the drawing and is blown off. On the other hand, a certain amount of previously deposited pigment is scraped off and picked up again soiling the tip. This is noticeable in the next strokes to be drawn. Furthermore, both the tip and the paper surface are subject to weathering depending on the exerted pressure and friction of the drawing tool, and the bumpiness of the paper. As a result, the paper surface becomes slightly damaged, limiting the deposition of new pigment. The tip, on the other hand, becomes blunt making new strokes wider.From a stylistic point of view, similarly to traditional drawings our results convey the artists’ characteristics (e.g., the way of wielding the brush, skillfulness, feeling for the medium). Therefore, we believe that our system allows an artist to create realistically looking pastel images without losing his/her personal touch.We present a system for drawing pastel media in real-time as an effective alternative to most existing digital solutions that basically allow for drawing arbitrary strokes in a particular style. Our approach is focused on the simulation of the natural material itself and on its interaction with the drawing surface and the drawing tool. Upon free-form drawing, a bidirectional transfer of pigment takes place. In one direction, the paper surface is dusted with new pigment particles broken off the tip (i.e., the end of the drawing tool). A large part of these particles will be deposited or blended together with previously deposited ones whereas the remainder does not contribute to the drawing and is blown off. On the other hand, a certain amount of previously deposited pigment is scraped off and picked up again soiling the tip. This is noticeable in the next strokes to be drawn. Furthermore, both the tip and the paper surface are subject to weathering depending on the exerted pressure and friction of the drawing tool, and the bumpiness of the paper. As a result, the paper surface becomes slightly damaged, limiting the deposition of new pigment. The tip, on the other hand, becomes blunt making new strokes wider. From a stylistic point of view, similarly to traditional drawings our results convey the artists’ characteristics (e.g., the way of wielding the brush, skillfulness, feeling for the medium). Therefore, we believe that our system allows an artist to create realistically looking pastel images without losing his/her personal touch.

Dip - it: digital infrared painting on an interactive table

In this paper we report on our work to develop a novel input technique for a digital paint system. Using a brush with infrared (IR) light emitting fibers, we were able to create a natural paint interface on an interactive table. This IR-brush adds two important properties to our paint environment: haptic feedback and an accurate brush footprint. The modified brush approaches the haptic feedback of the traditional paint brush. The use of IR-light in the brush enables tracking the contact area of the brush on the interactive table. Informal usability tests show that our digital paint environment offers an intuitive interface and contributes to an enhanced user experience in digital painting.

Brush up your painting skills: Realistic brush design for interactive painting applications

Most present-day interactive paint applications lack the means of adequately capturing a user’s gestures and translating them into realistic and predictable strokes, despite the importance of such a mechanism. We present a novel brush design that adopts constrained energy optimization to deform the brush tuft according to the user’s input movement. It incorporates bidirectional paint transfer and an anisotropic friction model. The main advantage of our method is its ability to handle a wide range of brush tuft shapes that are animated using a freeform deformation lattice, which is associated with the tuft’s geometry. This way, almost no conditions or limitations are placed upon the appearance of the brush. Examples range from round brushes modeled as polygon meshes, to flat brushes with individual bristles. Less common deformable tools that are used to apply or remove paint on the canvas, like sponges, can be created as well. The model is integrated in our interactive painting system for creating images with watery paint.Most present-day interactive paint applications lack the means of adequately capturing a user’s gestures and translating them into realistic and predictable strokes, despite the importance of such a mechanism. We present a novel brush design that adopts constrained energy optimization to deform the brush tuft according to the user’s input movement. It incorporates bidirectional paint transfer and an anisotropic friction model. The main advantage of our method is its ability to handle a wide range of brush tuft shapes that are animated using a freeform deformation lattice, which is associated with the tuft’s geometry. This way, almost no conditions or limitations are placed upon the appearance of the brush. Examples range from round brushes modeled as polygon meshes, to flat brushes with individual bristles. Less common deformable tools that are used to apply or remove paint on the canvas, like sponges, can be created as well. The model is integrated in our interactive painting system for creating images with watery paint.

Runtime transformations for modal independent user interface migration

Abstract The usage of computing systems has evolved dramatically over the last years. Starting from a low level procedural usage, in which a process for executing one or several tasks is carried out, computers now tend to be used in a problem oriented way. Future computer usage will be more centered around particular services, and will not be focused on platforms or applications. These services should be independent of the technology used to interact with them. In this paper an approach will be presented which provides a uniform interface to such services, without any dependence on modality, platform or programming language. Through the usage of general user interface descriptions, presented in XML, and converted using XSLT, a uniform framework is presented for runtime migration of user interfaces. As a consequence, future services will become easily extensible for all kinds of devices and modalities. Special attention goes out to a component-based software development approach. Services represented by and grouped in components can offer a special interface for modal- and device-independent rendering. Components become responsible for describing their own possibilities and constraints for interacting. An implementation serving as a proof of concept, a runtime conversion of a joystick in a 3D virtual environment into a 2D dialog-based user interface, is developed.

Real-time simulation of watery paint: Natural Phenomena and Special Effects

Not everything is perceived as it is provided by the environment. Depending on focus and attention perception can vary and therefore also the knowledge about the world. Virtual humans are sensing the virtual world, storing knowledge and using it to perform tasks. This paper describes our approach to model perceiving, storing and forgetting knowledge as the main regulation of tasks. We use different forms and levels of knowledge which can be independently adapted to different personalities and situations by combining computer graphics methods with psychological models. Copyright

Specifying User Interfaces for Runtime Modal Independent Migration

The usage of computing systems has evolved dramatically over the last years. Starting from a low level procedural usage, in which a process for executing one or several tasks is carried out, computers now tend to be used in a problem oriented way. Future computer usage will be more centered around particular services, and will not be focused on platforms or applications. These services should be independent of the technology used to interact with them. In this paper an approach will be presented which provides a uniform interface to such services, without any dependence on modality, platform or programming language. Through the usage of general user interface descriptions, presented in XML, and converted using XSLT, a uniform framework is presented for runtime migration of user interfaces. As a consequence, future services will become easily extensible for all kinds of devices and modalities. An implementation serving as a proof of concept, a runtime conversion of a joystick in a 3D virtual environment into a 2D dialog-based user interface, is developed.

Real-time simulation of thin paint media

The possibility of experimenting with various techniques and paint media, as well as the ability of introducing a wide range of digital tools, makes a digital equivalent of the traditional painting process a valuable asset for both novices and experienced artists. Existing work on applications for thin watery paint is mainly focused on automatic generation of painterly-style images from input images, ignoring the fact that painting is a process that intuitively should be interactive. Efforts to create real-time interactive systems are limited to a single paint medium and results often suffer from a trade-off between real-timeness and simulation complexity.

The pLab project: an extensible architecture for physically-based simulations

Pluggable architectures have become a popular means of creating extensible applications. Traditional plugins however are mostly fixed, single-purpose extensions that have only limited capabilities. We present a framework that allows the building of pluggable applications in which the plugins mainly deliver flexible building blocks or components that are put in place using an XML document. This way, the XML document actually serves as a blueprint of the component layout, instantiating the behavior of an application. The framework is to be used in combination with the ongoing research in the domain of physically-based modeling and simulation.