斯坦福大学 可编程 多材质 三维打印 siggraph 2013.pdf

OpenFab: A Programmable Pipeline for Multi-Material FabricationKiril Vidimˇ ceSzu-Po WangJonathan Ragan-KelleyWojciech MatusikMassachusetts Institute of TechnologyFigure 1: Three rhinos, defined and printed using OpenFab. For each print, the same geometry was paired with a different fablet—a shader-like program which procedurally defines surface detail and material composition throughout the object volume. This produces three unique prints by using displacements, texture mapping, and continuous volumetric material variation as a function of distance from the surface.Abstract3D printing hardware is rapidly scaling up to output continuous mixtures of multiple materials at increasing resolution over ever larger print volumes. This poses an enormous computational chal- lenge: large high-resolution prints comprise trillions of voxels and petabytes of data and simply modeling and describing the input with spatially varying material mixtures at this scale is challeng- ing.Existing 3D printing software is insufficient; in particular, most software is designed to support only a few million primitives, with discrete material choices per object. We present OpenFab, a programmable pipeline for synthesis of multi-material 3D printed objects that is inspired by RenderMan and modern GPU pipelines. The pipeline supports procedural evaluation of geometric detail and material composition, using shader-like fablets, allowing models tobe specified easily and efficiently. We describe a streaming archi-tecture for OpenFab; only a small fraction of the final volume is stored in memory and output is fed to the printer with little startup delay. We demonstrate it on a variety of multi-material objects.CR Categories:I.3.5 [Computer Graphics]: Computational Ge- ometry and Object Modeling—Curve, surface, solid, and object representation I.3.8 [Computer Graphics]: ApplicationsKeywords: fabrication, 3D printing, API, materialsLinks:DLPDFWEB1IntroductionState-of-the-art 3D printing hardware is capable of mixing many materials at up to 600 DPI resolution, using, for example, pho- topolymer phase-change inkjet technology. Each layer of the model is ultimately fed to the printer as a full-resolution bitmap whereeach “pixel” specifies a single material and all layers together de-fine on the order of 108voxels per cubic inch. This poses an enor- mous computational challenge as the resulting data is far too large to directly precompute and store; a single cubic foot at this resolu- tion requires at least 1011voxels, and terabytes of storage. Even for small objects, the computation, memory, and storage demands are large.At the same time, it is challenging for users to specify continuous multi-material mixtures at high resolution. Current printer software is designed to process polygon meshes with a single material per object. This makes it impossible to provide a continuous gradation between multiple materials, an important capability of the under- lying printer hardware that is essential to many advanced multi- material applications (e.g., [Wang et al. 2011]). Similarly, there isno support for decoupling material from geometry definition, and thus no ability to specify material templates that can be reused (e.g.,repeating a pattern that defines a composite material, or defining a procedural gradation for functionally graded materials).We think the right way to drive multi-material 3D printers is a pro- grammable synthesis pipeline, akin to the rendering pipeline. In- stead of a static mesh per piece of material, OpenFab describes aprocedural method to synthesize the final voxels of material at fullprinter resolution, on demand. This provides efficient storage and communication, as well as resolution independence for differenthardware and output contexts. It also decouples material definitionfrom geometry. A domain-specific language and pipeline featuresspecific to 3D printing make it much easier for users to specify many types of procedurally printed output than they could by writ- ing standalone programs for every different material or fabrication application.The OpenFab pipeline offers an expressive programming model for procedurally specifying the geometry and material of printable ob- jects. A scene graph describes geometry and attributes, while fa-blets procedurally modify the geometry and define material compo- sition much like shaders in the rendering pipeline. Fablets are writ-ten in a domain-specific language (OpenFL) and provide a flexibletoolset that supports many common material specification tasks.We also propose a scalable architecture for implementing the Open- Fab pipeline. Since the total computational cost is large and it is im-possible to fit the entire output volume into memory, the pipeline is designed to progressively stream output to the printer with minimal up-front precomputation and with only a small slab of the volume kept in memory at any one time. An OpenFL compiler analyzes and transforms the procedural computatio。