As the number of 3D models available on the Web grows, there is an increasing need for a search engine to help people find them. Unfortunately, traditional text-based search techniques are not always effective for 3D data. In this paper, we investigate new shape-based search methods. The key challenges are to develop query methods simple enough for novice users and matching algorithms robust enough to work for arbitrary polygonal models. We present a web-based search engine system that supports queries based on 3D sketches, 2D sketches, 3D

this paper, we propose and analyze a method for computing shape signatures for arbitrary (possibly degenerate) 3D polygonal models. The key idea is to represent the signature of an object as a shape distribution sampled from a shape function measuring global geometric properties of an object. The primary motivation for this approach is to reduce the shape matching problem to the comparison of probability distributions, which is simpler than traditional shape matching methods that require pose registration, feature correspondence, or model fitting

We present new methods for painterly video processing. Based on our earlier still image processing technique, we “paint over ” successive frames of animation, applying paint only in regions where the source video is changing. Image regions with minimal changes, such as due to video noise, are also left alone, using a simple difference masking technique. Optionally, brush strokes may be warped between frames using computed or procedural optical flow. These methods produce video with a novel visual style distinct from previously demonstrated algorithms. Without optical flow, the video gives the effect of a painting that has been repeatedly updated and photographed, similar to painton-glass animation. We feel that this gives a subjective impression of the work of a human hand. With optical flow, the painting surface flows and deforms to follow the shape of the world. We have constructed an interactive painting exhibit, in which a painting is continually updated. Viewers have found this to be a compelling experience, suggesting the promise of non-photorealistic rendering for creating compelling interactive visual experiences.

We present a new particle-based surface representation with which a user can interactively sculpt free-form surfaces. The particles maintain mesh connectivity and operate under rules that lead them to form triangulations with properties that make them suitable for use in subdivision. A user interactively guides the particles, which we call skin, to grow over a given collection of polyhedral elements (or skeletons), yielding a smooth surface (through subdivision) that approximates the underlying skeletal shapes. Skin resembles blobby modeling in the constructive approach to modeling it supports, but allows a richer vocabulary of skeleton shapes, supports sharp creases where desired, and provides a convenient mechanism for adding multiresolution surface detail. CR Categories and Subject Descriptors: I.3.5 [Computer Graphics ]: Computational Geometry and Object Modeling I.3.6 [Computer Graphics]: Methodology and Techniques Additional Key Words: Free-form modeling, meshes, subdivision, m...

CavePainting is an artistic medium that uses a 3D analog of 2D brush strokes to create 3D works of art in a fully immersive Cave environment. Physical props and gestures are used to provide an intuitive interface for artists who may not be familiar with virtual reality. The system is designed to take advantage of the 8 ft. x 8 ft. x 8 ft. space in which the artist works. CavePainting enables the artist to create a new type of art and provides a novel approach to viewing this art after it has been created. In this paper, we describe CavePainting 's 3D brush strokes, color pickers, artwork viewing mode, and interface. We also present several works of art created using the system along with feedback from artists. Artists are excited about this form of art and the gestural, full-body experience of creating it. CR Categories and Subject Descriptors: I.3.6 [Computer Graphics ]: Methodology and Techniques - Interaction Techniques; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Real...

The problem of interactively creating 3D scenes from 2D input is a compelling one, and recent progress has been exciting. We present our system, Harold, which combines ideas from existing techniques and introduces new concepts to make an interactive system for creating 3D worlds. The interface paradigm in Harold is drawing:all objects are created simply by drawing them with a 2D input device. Most of the 3D objects in Harold are collections of planar strokes that are reoriented in a view-dependent way as the camera moves through the world. Virtual worlds created in Harold are rendered with a stroke-based system so that a world will maintain a hand-drawn appearance as the user navigates through it. Harold is not suitable for representing certain classes of 3D objects, especially geometrically regular or extremely asymmetric objects. However, Harold supports a large enough class of objects that a user can rapidly create expressive and visually rich 3D worlds. CR Categories and Subject ...

We present a novel drawing system for composing and rendering perspective scenes. Our approach uses a projective 2D representation for primitives rather than a conventional 3D description. This allows drawings to be composed with the same ease as traditional illustrations, while providing many of the advantages of a 3D model. We describe a range of user-interface tools and interaction techniques that give our system its 3D-like capabilities. We provide vanishing point guides and perspective grids to aid in drawing freehand strokes and composing perspective scenes. Our system also has tools for intuitive navigation of a virtual camera, as well as methods for manipulating drawn primitives so that they appear to undergo 3D translations and rotations. We also support automatic shading of primitives using either realistic or non-photorealistic styles. Our system supports drawing and shading of extrusion surfaces with automatic hidden surface removal and highlighted silhouettes. Casting shadows from an infinite light source is also possible with minimal user intervention. CR Categories: I.3.3 [Computer Graphics]: Graphics Utilities--- Graphics Editors; I.3.6 [Computer Graphics]: Methodologies and Techniques---Interaction Techniques Keywords: Image-based Modeling and Rendering, Misc. 2D graphics, Non-Euclidean Spaces, Non-Photorealistic Rendering 1

We describe a novel continuous medial representation for object geometry and a deformable templates method for fitting the representation to images. Our representation simultaneously describes the boundary and medial loci of geometrical objects, always maintaining Blum’s symmetric axis transform (SAT) relationship. Cubic b-splines define the continuous medial locus and the associated thickness field, which in turn generate the object boundary. We present geometrical properties of the representation and derive a set of constraints on the b-spline parameters. The 2D representation encompasses branching medial loci; the 3D version can model objects with a single medial surface, and the extension to branching medial surfaces is a subject of ongoing research. We present preliminary results of segmenting 2D and 3D medical images. The representation is ultimately intended for use in statistical shape analysis.

We propose a method for creating 'smart' sketches of freeform 3D objects. A 2D sketch of an object drawn by the user is enriched with information about its 3D structure. With the help of our system, the user can rotate the created sketch of the object and view it from various angles. Since most of the user input is a traditional 2D sketch, the system is very easy to use and doesn't limit the user's creativity. Our approach closely simulates the way 3D objects are drawn by artists. The user first models by sketching a simple 3D skeleton of the desired object. A more detailed sketch of the object is drawn in 2D over the skeleton. The skeleton helps the user to maintain correct proportions while drawing. Using the 3D skeleton, the system helps the user rotate the sketch. This way a hybrid model of an object is created - although being essentially 2D, the model can be rotated smoothly and viewed from various angles.

All Rights Reserved, 2001“The camera cannot compete with painting so long as it cannot be used in heaven or in hell.”