Accurate color reproduction is important in many applications of 3D printing, from design prototypes to 3D color copies or portraits. Although full color is available via other technologies, multi-jet printers have greater potential for graphical 3D printing, in terms of reproducing complex appearance properties. However, to date these printers cannot produce full color, and doing so poses substantial technical challenges, from the shear amount of data to the translucency of the available color materials. In this article, we propose an error diffusion halftoning approach to achieve full color with multi-jet printers, which operates on multiple isosurfaces or layers within the object. We propose a novel traversal algorithm for voxel surfaces, which allows the transfer of existing error diffusion algorithms from 2D printing. The resulting prints faithfully reproduce colors, color gradients and fine-scale details.
Tone reproduction in FDM prints. Some recent work has focused on the challenging task of improving tone reproduction in fused deposition modeling (FDM) printing. Hergel and Lefebvre @cite_36 optimize seam placement in multi-filament FDM prints to hide or reduce artifacts from changing filaments. @cite_14 perform a type of halftoning for FDM printers while maintain long filament paths. Switching filament heads not only creates artifacts, but also increases print time. Both of these methods are specific to FDM printers.
@cite_36 @cite_14
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In this work we detail a method that leverages the two color heads of recent low-end fused deposition modeling FDM 3D printers to produce continuous tone imagery. The challenge behind producing such two-tone imagery is how to finely interleave the two colors while minimizing the switching between print heads, making each color printed span as long and continuous as possible to avoid artifacts associated with printing short segments. The key insight behind our work is that by applying small geometric offsets, tone can be varied without the need to switch color print heads within a single layer. We can now effectively print two-tone texture mapped models capturing both geometric and color information in our output 3D prints. Introduction AM Digital Halftoning FM Digital Halftoning AM-FM Hybrids AM Halftoning Dot Shape Screen Angles and Moire Screen Frequency Supercells Zero-Angle Dither Arrays Stochastic Halftone Analysis Point Processes Spatial Statistics Spectral Statistics Color Halftoning Halftone Visibility Campbell's CSF Model Nasanen (Exponential) Model Mixed Gaussian Models Alpha Stable HVS Models Blue-Noise Dithering Spatial and Spectral Characteristics Error Diffusion Blue-Noise Dither Arrays Simulated Annealing Void and Cluster BIPPSMA Dither Pattern Ordering Direct Binary Search Halftoning by DBS Efficient Implementation of DBS Effect of HVS model Hexagonal Grid Halftoning Spectral Aliasing Modified Blue-Noise Model Hexagonal Sampling Grids Printers: Distortions and Models Printer Distortion Dot Models Corrective Measures Green-Noise Dithering Spatial and Spectral Characteristics EDODF Green-Noise Masks BIPPCCA Optimal Green-Noise Masks Color Printing Generalized Error Diffusion Multichannel Green-Noise Masks Stochastic Moire Spatial Analysis of Periodic Moire Spatial Analysis of Aperiodic Moire Spectral Analysis of Aperiodic Moire Minimizing Stochastic Moire Stochastic Moire and Green-Noise Multitone Dithering Spectral Statistics of Multitones Multitone Blue-Noise Model Blue-Noise Multitoning Optimization Lenticular Halftoning Model Based Error Diffusion Iterative Tone Correction Conclusions Bibliography List of Figures Index In this paper, we explore the structure of light field (LF) and efficiently improve the performance of the pseudo sequence based lenslet image compression, by optimized sub-view rearrangement, enhanced illumination compensation and adaptive reconstruction filtering. First, the decomposed sub-view images are rearranged into a pseudo sequence according to our optimized scan order based on sub-view correlation. Second, the generated pseudo sequence is compressed with JEM codec in which we enhance the illumination compensation by adaptively selecting reference pixels used in parameter derivation. Finally, to reduce the distortions in lenslet image decomposition and reconstruction, we propose an lenslet reconstruction method by applying adaptive filters to the reconstructed lenslet images to compensate the reconstruction errors. Each filter is derived by minimizing the distortions between the original and reconstructed pixels with same geolocation in the lenslet image. Extensive experimental results show that the proposed method achieves up to 53.7 bit rate reduction over HEVC intra coding and 34.8 over JEM intra coding in terms of BDBR. Understanding and optimizing the properties of solar cells is becoming a key issue in the search for alternatives to nuclear and fossil energy sources. A theoretical analysis via numerical simulations involves solving Maxwell's Equations in discretized form and typically requires substantial computing effort. We start from a hybrid-parallel (MPI+OpenMP) production code that implements the Time Harmonic Inverse Iteration Method (THIIM) with Finite-Difference Frequency Domain (FDFD) discretization. Although this algorithm has the characteristics of a strongly bandwidth-bound stencil update scheme, it is significantly different from the popular stencil types that have been exhaustively studied in the high performance computing literature to date. We apply a recently developed stencil optimization technique, multicore wavefront diamond tiling with multi-dimensional cache block sharing, and describe in detail the peculiarities that need to be considered due to the special stencil structure. Concurrency in updating the components of the electric and magnetic fields provides an additional level of parallelism. The dependence of the cache size requirement of the optimized code on the blocking parameters is modeled accurately, and an auto-tuner searches for optimal configurations in the remaining parameter space. We were able to completely decouple the execution from the memory bandwidth bottleneck, accelerating the implementation by a factor of three to four compared to an optimal implementation with pure spatial blocking on an 18-core Intel Haswell CPU.