Fraunhofer IGD scientists develop new process to avoid stair-step artifacts

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Fraunhofer IGD scientists – Mostafa Morsy Abdelkader Morsy, Alan Brunton and Philipp Urban – whose “3D Printing Technology” department is responsible for the creation of the cuttlefish, have developed a purely geometric and algorithmic method for the elimination stair-step artifacts in multiple 3D-printed materials. To avoid quantization errors, the surface of the object is modulated with a high frequency signal. The result is geometrically precise and color-accurate surfaces. The research team has documented their findings in an article entitled “Shape Dithering for 3D Printing”, which will be published to coincide with SIGGRAPH, the premier conference and exhibition on computer graphics and interactive techniques – where the research will be presented by the lead author, Mostafa Morsy Abdelkader Morsy.

Jagged artifacts are unavoidable in conventional 3D printing processes. They are visually unattractive and can also be structurally detrimental in print. To generate more accurate surfaces, researchers at the Fraunhofer Institute for Computer Graphics Research IGD have developed a new process for polyjet printers – minimizing quantization errors so that jagged artifacts are no longer noticeable in the actual print and are far below the physical effects of the printing process. This results in objects with a smoother and more uniform surface.

“Quantification artifacts are a fundamental problem for all 3D printing technologies, but especially for multi-material jet printers. Despite their high solutions, stair artifacts (a) can be visually irritating and can structurally weaken the room [Moore and Williams 2015]. Existing techniques [Kritchman2010] (b) are limited to a specific surface orientation, introduce considerable additional computation, and do not remove all artifacts. Our purely geometric and algorithmic technique (c) removes staircase artifacts in all surface orientations, accounts for resolution anisotropy, and introduces minimal computational overhead. – Shape screening for 3D printing

To achieve the desired effect, the surface of the object is modulated with a high frequency signal, such as blue noise. This leads to a distribution of quantization errors at high frequencies, which are then suppressed by the function of the human eye and multiple printing processes. “The print time remains the same regardless of the process. The dithering process also does not require additional computation time,” explained Alan Brunton, a member of the three-author team.

The process is used, for example, in the entertainment industry, where characters and objects are printed for animated films, video games and board games. Unlike the previous processes, they benefit from the geometric and color precision conferred by the shape screening approach, which gives them a particularly realistic appearance.

The dithering process can be used as a purely algorithmic method, independent of hardware (i.e. with different polyjet 3D printers). The solution presented in the research paper is used with the Cuttlefish 3D printer driver developed by Fraunhofer IGD. Based on the now published results – in the future, scientists will investigate the further hypothesis of whether the smoother surface of printed objects also makes them stronger.

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