Normal meshes are new fundamental surface descriptions inspired by differential geometry. A normal mesh is a multiresolution mesh where each level can be written as a normal offset from a coarser version. Hence the mesh can be stored with a single float per vertex. We present an algorithm to approximate any surface arbitrarily closely with a normal semi-regular mesh. Normal meshes can be useful in numerous applications such as compression, filtering, rendering, texturing, and modeling.

Appearance reproduction is an important aspect of 3D printing. Current color reproduction systems use halftoning methods that create colors through a spatial combination of different inks at the object's surface. This introduces a variety of artifacts to the object, especially when viewed from a closer distance. In this work, we propose an alternative color reproduction method for 3D printing. Inspired by the inherent ability of 3D printers to layer different materials on top of each other, 3D color contoning creates colors by combining inks with various thicknesses inside the object's volume. Since inks are inside the volume, our technique results in a uniform color surface with virtually invisible spatial patterns on the surface. For color prediction, we introduce a simple and highly accurate spectral model that relies on a weighted regression of spectral absorptions. We fully characterize the proposed framework by addressing a number of problems, such as material arrangement, calculation of ink concentration, and 3D dot gain. We use a custom 3D printer to fabricate and validate our results.

Figure 1: Three rhinos, defined and printed using OpenFab. For each print, the same geometry was paired with a different fablet-a shaderlike 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 challenge: 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 challenging. 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 to be specified easily and efficiently. We describe a streaming architecture 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.

Figure 1: From left to right: 8x super-sample anti-aliasing (SSAA), 8x multi-sample anti-aliasing (MSAA) and surface-based anti-aliasing (SBAA) with 8 visibility and 2 surface samples per pixel. The circles represent visibility samples, while the blue and red discs represent shading samples from two different surfaces. The four red primitives sharing the same vertex are part of the same foreground surface. Our MERGE2 algorithm exploits this configuration and shades only one sample for all four red primitives while reserving a second surface sample for the blue background surface. Unlike multi-sampling, SBAA based algorithms impose an upper bound on the number of captured, stored and shaded surfaces rather than primitives in each pixel, therefore significantly reducing storage and shading costs. AbstractWe present surface based anti-aliasing (SBAA), a new approach to real-time anti-aliasing for deferred renderers that improves the performance and lowers the memory requirements for anti-aliasing methods that sample sub-pixel visibility. We introduce a novel way of decoupling visibility determination from shading that, compared to previous multi-sampling based approaches, significantly reduces the number of samples stored and shaded per pixel. Unlike postprocess anti-aliasing techniques used in conjunction with deferred renderers, SBAA correctly resolves visibility of sub-pixel features, minimizing spatial and temporal artifacts.

We introduce adaptive volumetric shadow maps (AVSM), a real-time shadow algorithm that supports high-quality shadowing from dynamic volumetric media such as hair and smoke. The key contribution of AVSM is the introduction of a streaming simplification algorithm that generates an accurate volumetric light attenuation function using a small fixed memory footprint. This compression strategy leads to high performance because the visibility data can remain in on-chip memory during simplification and can be efficiently sampled during rendering. We demonstrate that AVSM compression closely approximates the ground-truth correct solution and performs competitively to existing real-time rendering techniques while providing higher quality volumetric shadows.