A multi-axis robot-based bioprinting system supporting natural cell function preservation and cardiac tissue fabrication.

Despite the recent advances in artificial tissue and organ engineering, how to generate large size viable and functional complex organs still remains as a grand challenge for regenerative medicine. Three-dimensional bioprinting has demonstrated its advantages as one of the major methods in fabricating simple tissues, yet it still faces difficulties to generate vasculatures and preserve cell functions in complex organ production. Here, we overcome the limitations of conventional bioprinting systems by converting a six degree-of-freedom robotic arm into a bioprinter, therefore enables cell printing on 3D complex-shaped vascular scaffolds from all directions.

Mesh-Based Computation for Solving Photometric Stereo With Near Point Lighting.

We tackle the problem of dense reconstruction with a practical system, in which near point lighting (NPL) is employed. Different from the conventional formulation of photometric stereo (PS) that assumes parallel lighting, PS under the NPL condition is a nonlinear problem as the local surface normals are coupled with its distance to the camera as well as the light sources. After obtaining the locations of point lights by a calibration process, we develop a new framework to solve this nonlinear reconstruction problem via mesh deformation, in which each facet is corresponding to a pixel in the image captured by the camera.

Interactive Partitioning of 3D Models into Printable Parts.

In this paper, we present an easy, flexible and interactive tool for partitioning a 3D model, which is larger than 3D-printers working volume, into printable parts in an intuitive way. Our presented tool is based on the elegant partitioning optimization framework Chopper. Our tool aims at improving Chopper by providing users three easy-to-use interactive operations: no-go region painting, cutting plane specification and components re-union.

Bas-Relief Modeling from Normal Layers.

Bas-relief is characterized by its unique presentation of intrinsic shape properties and/or detailed appearance using materials raised up in different degrees above a background. However, many bas-relief modeling methods could not manipulate scene details well. We propose a simple and effective solution for two kinds of bas-relief modeling (i.

Support-Free Hollowing.

Offsetting-based hollowing is a solid modeling operation widely used in 3D printing, which can change the model's physical properties and reduce the weight by generating voids inside a model. However, a hollowing operation can lead to additional supporting structures for fabrication in interior voids, which cannot be removed. As a consequence, the result of a hollowing operation is affected by these additional supporting structures when applying the operation to optimize physical properties of different models.

Interactive Partitioning of 3D Models into Printable Parts.

This article presents an easy, flexible and interactive tool for partitioning a 3D model, which is larger than a 3D printers working volume, into printable parts in an intuitive way. Our tool is based on the elegant partitioning optimization framework Chopper. Our tool aims at improving Chopper by providing users three easy-to-use interactive operations: no-go region painting, cutting plane specification and components reunion.

Efficient C2-Weighting for Image Warping.

Handle-driven image warping based on linear blending is widely used in many applications because of its merits on intuitiveness, efficiency, and ease of implementation. In this paper, we develop a method to compute high-quality weights within a closed domain for image warping. The property of C2 continuity in weights is guaranteed by the carefully formulated basis functions.

Styling Evolution for Tight-Fitting Garments.

We present an evolution method for designing the styling curves of garments. The procedure of evolution is driven by aesthetics-inspired scores to evaluate the quality of styling designs, where the aesthetic considerations are represented in the form of streamlines on human bodies. A dual representation is introduced in our platform to process the styling curves of designs, based on which robust methods for realizing the operations of evolution are developed.

Highly parallel algorithms for visual-perception-guided surface remeshing.

A proposed framework for remeshing polygonal models employs mesh-free techniques for processing surface sample points. It's robust to input models with problematic connectivity, and the geometric processing of points runs easily in parallel on a GPU. The framework extracts visual-perception information in the image space and maps it back to the Euclidean space.

Conservative sampling of solids in image space.

Conservative sampling samples boundary-representation (B-rep) solid models into layered depth images (LDIs). The resulting models have a closed boundary and are guaranteed to bound the input B-rep models on the rays of LDIs. This approach can be fully implemented by shader programs supported by various graphics hardware.

Iterative consolidation of unorganized point clouds.

Unorganized point clouds obtained from 3D shape acquisition devices usually present noise, outliers, and nonuniformities. The proposed framework consolidates unorganized points through an iterative procedure of interlaced downsampling and upsampling. Selection operations remove outliers while preserving geometric details.

Efficient Boundary Extraction of BSP Solids Based on Clipping Operations.

We present an efficient algorithm to extract the manifold surface that approximates the boundary of a solid represented by a Binary Space Partition (BSP) tree. Our polygonization algorithm repeatedly performs clipping operations on volumetric cells that correspond to a spatial convex partition and computes the boundary by traversing the connected cells. We use point-based representations along with finite-precision arithmetic to improve the efficiency and generate the B-rep approximation of a BSP solid.

Efficient optimization of common base domains for cross parameterization.

Given a set of corresponding user-specified anchor points on a pair of models having similar features and topologies, the cross parameterization technique can establish a bijective mapping constrained by the anchor points. In this paper, we present an efficient algorithm to optimize the complexes and the shape of common base domains in cross parameterization for reducing the distortion of the bijective mapping. The optimization is also constrained by the anchor points.

From designing products to fabricating them from planar materials.

A geometric-modeling system automates design and fabrication of products customized for consumers. Specifically, it maps designs onto different reference model shapes and then unfolds them into 2D pattern pieces. A map-guided algorithm automatically positions the pieces according to industrial requirements.

Approximate Boolean Operations on Large Polyhedral Solids with Partial Mesh Reconstruction.

We present a new approach to compute the approximate Boolean operations of two freeform polygonal mesh solids efficiently with the help of Layered Depth Images (LDIs). After applying the LDI sampling-based membership classification, the most challenging part, a trimmed adaptive contouring algorithm, is developed to reconstruct the mesh surface from the LDI samples near the intersected regions and stitch it to the boundary of the retained surfaces. Our method of approximate Boolean operations holds the advantage of numerical robustness as the approach uses volumetric representation.

Fast query for exemplar-based image completion.

In this paper, we present a fast algorithm for filling unknown regions in an image using the strategy of exemplar-matching. Unlike the original exemplar-based method using exhaustive search, we decompose exemplars into the frequency coefficients and select fewer coefficients which are the most significant to evaluate the matching score. We have also developed a local gradient-based algorithm to fill the unknown pixels in a query image block.

Interactive control of large-crowd navigation in virtual environments using vector fields.

Providing interactive control is a hot topic in crowd-navigation research. Here, the authors propose a simple but effective way for authoring a crowd scene. With their governing tool, users can easily drive the flow of crowds by sketching velocities on anchor points in the scene.

Mesh composition on models with arbitrary boundary topology.

This paper presents a new approach for the mesh composition on models with arbitrary boundary topology. After cutting the needed parts from existing mesh models and putting them into the right pose, an implicit surface is adopted to smoothly interpolate the boundaries of models under composition. An interface is developed to control the shape of the implicit transient surface by using sketches to specify the expected silhouettes.

Bilateral recovering of sharp edges on feature-insensitive sampled meshes.

A variety of computer graphics applications sample surfaces of 3D shapes in a regular grid without making the sampling rate adaptive to the surface curvature or sharp features. Triangular meshes that interpolate or approximate these samples usually exhibit relatively big error around the insensitive sampled sharp features. This paper presents a robust general approach conducting bilateral filters to recover sharp edges on such insensitive sampled triangular meshes.