3D Softproof for an accurate simulation of volumetric light transport effects ...

With the aim of improving the predictability of the visual appearance of 3D prints with scattering materials in full-colour 3D printing, particularly with regard to translucency, three main areas were pursued in this project. In the first focus area, simulations were developed for the correct visualisation of the translucency of 3D-printed objects. In the second focus area, the characterisation of the materials used in 3D printing was simplified so that the optical properties can be estimated using measurements with a spectrophotometer. The third focus area was dedicated to 3D colour communication and standardisation for full-colour 3D printing.

As part of the first focus, the research renderer was (further) developed with the aim of achieving a realistic representation of translucency in 3D prints. The renderer developed in the previous project, which simulates the appearance from the optical properties of materials and their exact geometric positioning, was optimised to achieve colour deviations CIEDE2000 of less than 2. Furthermore, an additional renderer was developed that simulates a representative appearance on the basis of RGBA definitions.

The second focus was on characterising the optical properties of the inks typically used in graphic 3D printing. Firstly, the optical properties, i.e. the refractive index, the scattering anisotropy factor, the absorption coefficient and the effective scattering coefficient, were precisely measured using laboratory equipment. This was followed by a systematic investigation of the optical properties of material mixtures. The aim of these investigations was to predict the optical properties of the material mixtures from the optical properties of the base materials. Subsequently, a new method for estimating the optical properties of a 3D print was designed and implemented using simpler measuring devices. For this purpose, an exemplary measuring head of a commercially available spectrophotometer was simulated. Deep learning algorithms then make it possible to calculate the optical properties.

The third focus was on advancing colour communication in full-colour 3D printing. This was achieved by developing an exchange colour space and investigating the representation of colour and translucency in common 3D printing tools. In addition, the international standardisation of the alpha parameter (ISO 19307) for the sensitive determination of translucency was supported. Furthermore, new solutions for measuring the alpha parameter were discussed and alternative methods for sorting 3D objects based on their translucency were investigated.