A Multiscale Microfacet Model Based on Inverse Bin Mapping
Accurately controllable shading detail is a crucial aspect of realistic appearance modelling. Two fundamental building blocks for this are microfacet BRDFs, which describe the statistical behaviour of infinitely small facets, and normal maps, which provide user-controllable spatio-directional surface features. We analyse the filtering of the combined effect of a microfacet BRDF and a normal map. By partitioning the half-vector domain into bins we show that the filtering problem can be reduced to evaluation of an integral histogram (IH), a generalization of a summed-area table (SAT). Integral histograms are known for their large memory requirements, which are usually proportional to the number of bins. To alleviate this, we introduce Inverse Bin Maps, a specialised form of IH with a memory footprint that is practically independent of the number of bins. Based on these, we present a memory-efficient, production-ready approach for filtering of high resolution normal maps with arbitrary Beckmann flake roughness.
Neural Acceleration of Scattering-Aware Color 3D Printing
With the wider availability of full-color 3D printers, color-accurate 3D-print preparation has received increased attention. A key
|31.3.2021||No meeting today|
One of the important steps in modeling realistic 3D scenes is setting material appearance of the various scene objects. The goal of our ongoing project is to simplify this often tedious task by providing the 3D artist with an intelligent material picker tool. The tool should allow user to ‘pick’ a material from any given input image by simply pointing to an object. A deep neural network will be trained to achieve this nontrivial goal. An extensive set of training data will be provided, where the complex correspondence between the image pixels and the underlying object material will be available. The network should be then able to recover this pixel-material correspondence from new, previously unseen images.
|14.4.2021||No meeting today|
Efficient Material Reflectance Representation and Editing
Computer graphics is a valuable tool used from industrial applications to entertainment; it enables creation of images from virtual scenes. One of the aims of computer graphics is to generate photorealistic scenes; an important part of realism is relying on the accuracy of material models. Hence, the study of material models and reflectance is crucial. Recently, measured materials gained popularity. This works well for uniform materials but spatially varying materials present multiple challenges in acquisition, storage, rendering and editing.In this presentation, we introduce improvements made to efficiently represent acquired reflectance by reducing memory footprint and allowing artists to edit the appearance of measured materials. These two improvements, memory footprint and editing capabilities makes measured materials practical in production scenes.
Constrained spectral uplifting
Physically-based spectral rendering is becoming increasingly popular in both commercial and academic areas due to its ability to accurately simulate natural phenomena. However, the production of materials defined by their spectral properties is a tedious and expensive process, which makes the utilization of RGB-based assets in spectral renderers a desired feature. To convert RGB values to their spectral representations, a process called spectral uplifting is employed. As the RGB color space is a finite subset of the visible gamut, there exist multiple conversion techniques producing distinct results, which may cause color inconsistencies under various lighting conditions. This thesis proposes a method for constraining the spectral uplifting process. To be specific, pre-defined mappings of RGB values to their spectral representations are preserved and the rest of the RGB gamut is plausibly uplifted. In order to assess its correctness, this technique is then implemented and evaluated in a spectral renderer. The renders uplifted via our method show minimal discrepancies when compared to the original textures.
A Gradient-Based Framework for 3D Print Appearance OptimizationIn full-color inkjet 3D printing, a key problem is determining the material configuration for the millions of voxels that a printed object is made of. The goal is a configuration that minimises the difference between desired target appearance and the result of the printing process. So far, the techniques used to find such a configuration have relied on domain-specific methods or heuristic optimization, which allowed only a limited level of control over the resulting appearance. We propose to use differentiable volume rendering in a continuous material mixture space, which leads to a framework that can be used as a general tool for optimising inkjet 3D printouts. We demonstrate the technical feasibility of this approach, and use it to attain fine control over the fabricated appearance, and high levels of faithfulness to the specified target.
A Fitted Radiance and Attenuation Model for Realistic Atmospheres
We present a fitted model of sky dome radiance and attenuation for realistic terrestrial atmospheres. Using scatterer distribution data from atmospheric measurement data, our model considerably improves on the visual realism of existing analytical clear sky models, as well as of interactive methods that are based on approximating atmospheric light transport. We also provide features not found in fitted models so far: radiance patterns for post-sunset conditions, in-scattered radiance and attenuation values for finite viewing distances, an observer altitude resolved model that includes downward-looking viewing directions, as well as polarisation information. We introduce a fully spherical model for in-scattered radiance that replaces the family of hemispherical functions originally introduced by Perez e.a., and which was extended for several subsequent analytical models: our model relies on reference image compression via tensor decomposition instead.
Gradient boosted segmentation of retinal fundus images
Diploma thesis defense rehearsal
Efficient light transport simulation of participating media in color 3D printing.
Diploma thesis defense rehearsal
(Excursion ideas: Eli, other VFX houses, Metrology institute, Valeo, CIIRC, VRgineers, liv.tv)