71,138 research outputs found
Orthogonal Array Sampling for Monte Carlo Based Rendering
In computer graphics (especially in offline rendering), the current state of the art rendering techniques utilize Monte Carlo integration to simulate light and calculate the value of each pixel in order to generate a realistic-looking image. Monte Carlo integration is a highly efficient method to estimate an integral that scales extremely well to a high number of dimensions, making it well suited for graphics, because generating images creates a high-dimensional integrand. The efficiency of these Monte Carlo integrations depends on the sampling techniques used, and using a more efficient sampling technique can make a Monte Carlo simulation converge to the right answer quicker than using more naive sampling techniques. In this thesis, we present an efficient sampling method that demonstrates much higher performance than many other sampling techniques. This novel sampling method, based on orthogonal arrays, offers guaranteed stratification in arbitrary projections, leading to better theoretical performance with integrands that have cross-correlated variance compared to sampling methods that do not offer these same guarantees
DIP: Differentiable Interreflection-aware Physics-based Inverse Rendering
We present a physics-based inverse rendering method that learns the
illumination, geometry, and materials of a scene from posed multi-view RGB
images. To model the illumination of a scene, existing inverse rendering works
either completely ignore the indirect illumination or model it by coarse
approximations, leading to sub-optimal illumination, geometry, and material
prediction of the scene. In this work, we propose a physics-based illumination
model that explicitly traces the incoming indirect lights at each surface point
based on interreflection, followed by estimating each identified indirect light
through an efficient neural network. Furthermore, we utilize the Leibniz's
integral rule to resolve non-differentiability in the proposed illumination
model caused by one type of environment light -- the tangent lights. As a
result, the proposed interreflection-aware illumination model can be learned
end-to-end together with geometry and materials estimation. As a side product,
our physics-based inverse rendering model also facilitates flexible and
realistic material editing as well as relighting. Extensive experiments on both
synthetic and real-world datasets demonstrate that the proposed method performs
favorably against existing inverse rendering methods on novel view synthesis
and inverse rendering
A Dual-Beam Method-of-Images 3D Searchlight BSSRDF
We present a novel BSSRDF for rendering translucent materials. Angular
effects lacking in previous BSSRDF models are incorporated by using a dual-beam
formulation. We employ a Placzek's Lemma interpretation of the method of images
and discard diffusion theory. Instead, we derive a plane-parallel
transformation of the BSSRDF to form the associated BRDF and optimize the image
confiurations such that the BRDF is close to the known analytic solutions for
the associated albedo problem. This ensures reciprocity, accurate colors, and
provides an automatic level-of-detail transition for translucent objects that
appear at various distances in an image. Despite optimizing the subsurface
fluence in a plane-parallel setting, we find that this also leads to fairly
accurate fluence distributions throughout the volume in the original 3D
searchlight problem. Our method-of-images modifications can also improve the
accuracy of previous BSSRDFs.Comment: added clarifying text and 1 figure to illustrate the metho
Path-tracing Monte Carlo Library for 3D Radiative Transfer in Highly Resolved Cloudy Atmospheres
Interactions between clouds and radiation are at the root of many
difficulties in numerically predicting future weather and climate and in
retrieving the state of the atmosphere from remote sensing observations. The
large range of issues related to these interactions, and in particular to
three-dimensional interactions, motivated the development of accurate radiative
tools able to compute all types of radiative metrics, from monochromatic, local
and directional observables, to integrated energetic quantities. In the
continuity of this community effort, we propose here an open-source library for
general use in Monte Carlo algorithms. This library is devoted to the
acceleration of path-tracing in complex data, typically high-resolution
large-domain grounds and clouds. The main algorithmic advances embedded in the
library are those related to the construction and traversal of hierarchical
grids accelerating the tracing of paths through heterogeneous fields in
null-collision (maximum cross-section) algorithms. We show that with these
hierarchical grids, the computing time is only weakly sensitivive to the
refinement of the volumetric data. The library is tested with a rendering
algorithm that produces synthetic images of cloud radiances. Two other examples
are given as illustrations, that are respectively used to analyse the
transmission of solar radiation under a cloud together with its sensitivity to
an optical parameter, and to assess a parametrization of 3D radiative effects
of clouds.Comment: Submitted to JAMES, revised and submitted again (this is v2
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