Dynamic Light Sources Research Articles

NeRC: Rendering Planar Caustics by Learning Implicit Neural Representations.

Caustics are challenging light transport effects for photo-realistic rendering. Photon mapping techniques play a fundamental role in rendering caustics. However, photon mapping methods render single caustics under the stationary light source in a fixed scene view. They require significant storage and computing resources to produce high-quality results. In this paper, we propose efficiently rendering more diverse caustics of a scene with the camera and the light source moving. We present a novel learning-based volume rendering approach with implicit representations for our proposed task. Considering the variety of materials and textures of planar caustic receivers, we decompose the output appearance into two components: the diffuse and specular parts with a probabilistic module. Unlike NeRF, we construct weights for rendering each component from the implicit signed distance function (SDF). Moreover, we introduce the centering calibration and the sine activation function to improve the performance of the color prediction network. Extensive experiments on the synthetic and real-world datasets illustrate that our method achieves much better performance than baselines in the quantitative and qualitative comparison, for rendering caustics in novel views with the dynamic light source. Especially, our method outperforms the baseline on the temporal consistency across frames.

Illuminating palaeolithic art using virtual reality: A new method for integrating dynamic firelight into interpretations of art production and use

Approaches to Palaeolithic art have increasingly shifted beyond the traditional focus on engraved or depicted forms in isolation, to appreciating the sensorial experience of art making as integral to shaping the form of depictions and the meaning imbued within them. This kind of research appreciates an array of factors pertinent to how the art may have been understood or experienced by people during the Palaeolithic, including placement, lighting, accessibility, sound, and tactility. This paper contributes to this “sensory turn” in Palaeolithic art research, arguing that the roving light cast by the naked flame of fires, torches or lamps is an important dimension in understanding artistic experiences. However, capturing these effects, whether during analysis, as part of interpretation, or presentation, can be challenging. A new method is presented in virtual reality (VR) modelling – applied to Palaeolithic art contexts for the first time - as a safe and non-destructive means of simulating dynamic light sources to facilitate analysis, interpretation, and presentation of Palaeolithic art under actualistic lighting conditions. VR was applied to two Magdalenian case studies: parietal art from Las Monedas (Spain) and portable stone plaquettes from Montastruc (France). VR models were produced using Unity software and digital models of the art captured via whitelight (Montastruc) and photogrammetric (Las Monedas) scans. The results demonstrate that this novel application of VR facilitates the testing of hypotheses related to the sensorial and experiential dimensions of Palaeolithic art, allowing discussions of these elements to be elevated beyond theoretical ideas.

Foveated Stochastic Lightcuts.

Foveated rendering provides an idea for accelerating rendering algorithms without sacrificing the perceived rendering quality in virtual reality applications. In this paper, we propose a foveated stochastic lightcuts method to render high-quality many-lights illumination effects in high perception-sensitive regions. First, we introduce a spatiotemporal-luminance based lightcuts generation method to generate lightcuts with different accuracy for different visual perception-sensitive regions. Then we propose a multi-resolution light samples selection method to select the light sample for each node in the lightcuts more efficiently. Our method supports full-dynamic scenes containing over 250k dynamic light sources and dynamic diffuse/specular/glossy objects. It provides frame rates up to 110fps for high-quality many-lights illumination effects in high perception-sensitive regions of the HVS in VR HMDs. Compared with the state-of-the-art stochastic lightcuts method using the same rendering time, our method achieves smaller mean squared errors in the fovea and periphery. We also conduct user studies to prove that the perceived quality of our method has a high visual similarity with the results of the ground truth rendered by using the stochastic lightcuts with 2048 light samples per pixel.

Optimization of the dynamic light source considering human age effect on visual and non-visual performances

The spectral transmittance of ocular media on the short-wavelength light is higher for young observers than elders. It is essential to concentrate on the photobiological safety of children and circadian effect of elders when designing the light sources. In this study, we optimized the peak wavelengths and ratios of four-channel light emitting-diodes (LEDs), to fabricate the dynamic white light which performed well on photobiological safety, circadian effect, and color rendition for observers of different ages. Based on the optimal results, we selected the four monochromatic LEDs of 461.0, 525.0, 589.0, and 660.0 nm, and then fabricated the practical white light. The correlated color temperature (CCT) of the dynamic white light is tunable from 2700 to 6500 K. For 1-year-old observers, the blue light hazard efficiency of radiation (BLHER) is less than 0.237. For 70-year-old observers, the melanopic efficacy of luminous radiation (MELR) reaches 0.987 mW/lm and its tunability is optimized to be 2.10. The general color rendering index (Ra), special color rendering index (R9), color fidelity index (Rf), and color gamut index (Rg) are more than 89.3, 79.1,81.7, and 93.6, respectively. At last, we also discussed the impacts of the peak wavelength variation on the performances of hybrid white light.

Dynamic spectral compensation of white LEDs in underwater illumination

Based on Mie scattering and Monte Carlo ray tracing method, the spectral transmission behavior of visible light in the seawater is estimated. Its optical model is constructed for the fast and accurate prediction of light quality changes of phosphor-based white LED underwater illumination with distance. Because of this, we propose to add a dual-wavelength LED to the original white LED, which would perform spectrum compensation at each illumination distance to restore its good light quality. The result shows that such a dynamic light source can successfully maintain correlated color temperature at 6000 K and color rendering index above 80 under different underwater illumination distances.

Foveated light culling

In this paper, we propose a novel Foveated Light Culling (FLC) method to efficiently approximate global illumination for foveated rendering in virtual reality applications. The key idea is to cull the virtual point lights (VPLs) in accordance with their contribution to the visual perception, which makes the loss of details caused is imperceptible to the human eyes. Based on this idea and the features of human visual system (HVS), we calculate the contribution of each VPL according to samples generated from a perceptual importance map. By estimating the local visibility between VPLs and samples, our method can greatly improve the performance during the process of evaluating contributions. Our method is able to produce high-quality single-bounce diffuse-to-diffuse indirect illumination in the foveal region at real-time frame rate while supporting dynamic scenes and light sources. Furthermore, the experiments show that our approach makes a good balance between foveal quality and render efficiency.

Real-time indirect illumination by virtual planar area lights

This paper presents a method called Virtual Planar Area Lights (VPALs) to generate single-bounce diffuse-to-diffuse indirect illumination for dynamic scenes and light sources. Different from the VPLs (Virtual Point Lights) based methods, which extract point lights from RSM (Reflective Shadow Map), our method fits RSM by many planar regions which will be directly used as virtual light sources to generate the indirect illumination. In order to reduce the illumination errors introduced by plane fitting, we propose several strategies, including an illumination-guided plane fitting algorithm, a normal correction factor and a virtual light sources reuse strategy. Our experimental results indicate that our method can achieve a good balance between the rendering performance and quality. Compared with traditional light culling and clustering methods, the rendering consumption of our algorithm is reduced by at least 67% with the similar RMSE (Root Mean Squared Error).

On-line state observation and fault diagnosis of high-power LED array dynamic light source based on dynamic kernel principal component analysis

大功率LED阵列动态光源工作过程中光电热参数具有不确定性和时变时滞非线性特点，利用动态核主元分析方法（DKPCA）对大功率LED阵列动态光源进行在线状态观测与故障诊断能有效地捕捉观测数据的非线性和相关性特征，根据历史数据的主元特征计算出的统计量阈值和在线数据的统计特征实现故障检测，利用重构贡献图法实现故障的分离。仿真实验表明，对大功率LED阵列动态光源典型的传感器和执行器故障进行有效监测和诊断相对于核主元分析方法对故障更为敏感，故障检测率最高提高了7.5%，误检率下降了4.2%。

Efficiently reconstruct light field probes from light-G-buffers

In this paper, we extend the light field probe method to handle dynamic light sources. The key idea is to generate distance and material information at the light source position on-the-fly and store them in a data structure called light-G-buffer. Based on this data structure and the precomputed geometric information, an efficient method is proposed to reconstruct the (ir)radiance fields for all light field probes, from which indirect diffuse and glossy illumination effects can be achieved for dynamic light sources. Furthermore, we show the ability of our method to handle multi-bounce lighting and accommodate multi-light environments at the cost of shading accuracy. Experiments show that our approach achieves comparable effects to the precomputed light field probe method at a real-time frame rate and can further handle multiple dynamic light sources.

Coordinate transformation of three-dimensional image in integral imaging system illuminated by a point light source

The point light source is an important kind of directional light source. By using directional illumination, the performances of the integral imaging system will be enhanced. In this paper, the coordinate transformation characteristics of integral imaging systems illuminated by a point light source have been explored in detail. By using a dynamic point light source such as a moving light emitting diode to illuminate the imaging system, the position and size of the rendered three-dimensional image can be transformed in real time without updating the elemental images, and the depth of field of the imaging system is doubled. The coordinates of the three-dimensional image are changed with the distance between the point light source and the micro-lens array. The optical mechanism of the three-dimensional dynamic imaging phenomenon is analyzed. The coordinate transformation rules of the three-dimensional image are deduced and verified by experiments. The phenomenon may find potential applications in interactively three-dimensional display or augmented reality system.

The evening light environment in hospitals can be designed to produce less disruptive effects on the circadian system and improve sleep.

Study ObjectivesBlue-depleted lighting reduces the disruptive effects of evening artificial light on the circadian system in laboratory experiments, but this has not yet been shown in naturalistic settings. The aim of the current study was to test the effects of residing in an evening blue-depleted light environment on melatonin levels, sleep, neurocognitive arousal, sleepiness, and potential side effects.MethodsThe study was undertaken in a new psychiatric hospital unit where dynamic light sources were installed. All light sources in all rooms were blue-depleted in one half of the unit between 06:30 pm and 07:00 am (melanopic lux range: 7–21, melanopic equivalent daylight illuminance [M-EDI] range: 6–19, photopic lux range: 55–124), whereas the other had standard lighting (melanopic lux range: 30–70, M-EDI range: 27–63, photopic lux range: 64–136), but was otherwise identical. A total of 12 healthy adults resided for 5 days in each light environment (LE) in a randomized cross-over trial.ResultsMelatonin levels were less suppressed in the blue-depleted LE (15%) compared with the normal LE (45%; p = 0.011). Dim light melatonin onset was phase-advanced more (1:20 h) after residing in the blue-depleted LE than after the normal LE (0:46 h; p = 0.008). Total sleep time was 8.1 min longer (p = 0.032), rapid eye movement sleep 13.9 min longer (p < 0.001), and neurocognitive arousal was lower (p = 0.042) in the blue-depleted LE. There were no significant differences in subjective sleepiness (p = 0.16) or side effects (p = 0.09).ConclusionsIt is possible to create an evening LE that has an impact on the circadian system and sleep without serious side effects. This demonstrates the feasibility and potential benefits of designing buildings or hospital units according to chronobiological principles and provide a basis for studies in both nonclinical and clinical populations.

Spatiotemporal reservoir resampling for real-time ray tracing with dynamic direct lighting

Efficiently rendering direct lighting from millions of dynamic light sources using Monte Carlo integration remains a challenging problem, even for off-line rendering systems. We introduce a new algorithm---ReSTIR---that renders such lighting interactively, at high quality, and without needing to maintain complex data structures. We repeatedly resample a set of candidate light samples and apply further spatial and temporal resampling to leverage information from relevant nearby samples. We derive an unbiased Monte Carlo estimator for this approach, and show that it achieves equal-error 6×-60× faster than state-of-the-art methods. A biased estimator reduces noise further and is 35×-65× faster, at the cost of some energy loss. We implemented our approach on the GPU, rendering complex scenes containing up to 3.4 million dynamic, emissive triangles in under 50 ms per frame while tracing at most 8 rays per pixel.

Detecting Specular Reflections and Cast Shadows to Estimate Reflectance and Illumination of Dynamic Indoor Scenes.

The goal of Mixed Reality (MR) is to achieve a seamless and realistic blending between real and virtual worlds. This requires the estimation of reflectance properties and lighting characteristics of the real scene. One of the main challenges within this task consists in recovering such properties using a single RGB-D camera. In this article, we introduce a novel framework to recover both the position and color of multiple light sources as well as the specular reflectance of real scene surfaces. This is achieved by detecting and incorporating information from both specular reflections and cast shadows. Our approach is capable of handling any textured surface and considers both static and dynamic light sources. Its effectiveness is demonstrated through a range of applications including visually-consistent mixed reality scenarios (e.g., correct real specularity removal, coherent shadows in terms of shape and intensity) and retexturing where the texture of the scene is altered whereas the incident lighting is preserved.

Quad‐Based Fourier Transform for Efficient Diffraction Synthesis

AbstractFar‐field diffraction can be evaluated using the Discrete Fourier Transform (DFT) in image space but it is costly due to its dense sampling. We propose a technique based on a closed‐form solution of the continuous Fourier transform for simple vector primitives (quads) and propose a hierarchical and progressive evaluation to achieve real‐time performance. Our method is able to simulate diffraction effects in optical systems and can handle varying visibility due to dynamic light sources. Furthermore, it seamlessly extends to near‐field diffraction. We show the benefit of our solution in various applications, including realistic real‐time glare and bloom rendering.

Evaluation of a light controller for a LED-based dynamic light source

In this paper, the performance of a dynamic light controller (DLC) is experimentally evaluated to achieve a dynamic light source consisting of alternative arrays of warm white and cool white light-emitting diodes (LEDs). The DLC is programmed to drive the light source through both step and continuous variations of correlated colour temperature (CCT) and light output. For step variation, the DLC generates pulse width modulation (PWM) signals to drive the LED arrays to achieve 16 desired set points out of four CCTs (2900–5600 K) and four illuminances (100–300 Lux). The measured set points show deviations within acceptable limits. For continuous variation, the DLC is programmed to make the dynamic light source follow a time-varying pattern of CCT and Illuminance. The variations of measured values are mostly within acceptable limits except at lower CCT and illuminance points. The measured duty cycles of the generated PWM signals from the DLC are almost equal to the corresponding calculated values for both the step and continuous variations indicating good performance. The measured deviations are caused by the differences in lumen output at duty cycles &lt;10% compared to the estimated values.

Accelerating Many-Lights Rendering with Multi-directional Scene Voxelization

Many scenes of interest to computer graphics applications contain a large number of dynamic light sources. Lighting is computationally expensive because it implies solving a visibility problem for every point light source. We present a method for voxel based approximation of the geometry of a scene. The ray is intersected with the approximation to accelerate the visibility determination. The scene geometry is approximated with a 2D array of voxelizations, with one voxelization for each direction from a dense sampling of the 2D space of all possible directions. The ray/scene intersection is approximated using the voxelization whose rows are most closely aligned with the ray. We support dynamic scenes with rigidly moving objects and complex dynamic scenes. The results of our experiments show our method can render scenes containing thousands lights.

The Method of Dynamic Measurement in Light Distribution Performance Test

&lt;p class="p0"&gt;In order to realize the measurement of dynamic light, a new measurement method of dynamic gain adjustment was proposed in this paper. And the method is combined hardware with software by the programmable amplifier with microprocessor. The value of signal peak is stayed by the peak hold circuit to be reference for gain amplifier. The test speed of dynamic light source is increased greatly through using this method. The dynamic source light can be measured in real-time by programmable gain instrument amplifier which is controlled by microprocessor. The result shows that the measurement error can be reduced to 0.1% in range of the light intensity at 1cd- 2400cd by this method.&lt;/p&gt;

Measuring the dynamics of contrast & daylight variability in architecture: A proof-of-concept methodology

Unlike artificial light sources, which can be calibrated to meet a desired luminous effect regardless of latitude, climate, or time of day, daylight is a dynamic light source, which produces variable shadow patterns and fluctuating levels of brightness. While we know that perceptual impacts of daylight such as contrast and temporal variability are important factors in architectural design, we are left with an imbalanced set of performance indicators – and few, if any, which address the positive visual and temporal qualities of daylight from an occupant point-of-view. If visual characteristics of daylight, such as contrast and spatial compositions, can be objectively measured, we can contribute to a more holistic analysis of daylit architecture with metrics that complement existing illumination and comfort-based performance criteria. Using image processing techniques, this paper will propose a proof-of-concept methodology for quantifying contrast-based visual effects within renderings of daylit architecture. Two new metrics will be proposed; annual spatial contrast and annual luminance variability. Using 56 time-step instances (taken symmetrically from across the day and year) this paper will introduce a method for quantifying local contrast values within a set of rendered images and plot those instances over time to visualize hourly and seasonal fluctuations in contrast composition. Using the same 56 instances, this paper will also introduce a method for quantifying variations in luminance (brightness) between instances to measure fluctuations in brightness. This paper pre-validates each of the proposed methods by calculating annual spatial contrast and annual luminance variability across ten abstract digital models and comparing those results to the authors' own intuitive ranking.

Effects of strobe light stimulation on postnatal developing rat retina

The nature and intensity of visual stimuli have changed in recent years because of television and other dynamic light sources. Although light stimuli accompanied by contrast and strength changes are thought to have an influence on visual system development, little information is available on the effects of dynamic light stimuli such as a strobe light on visual system development. Thus, this study was designed to evaluate changes caused by dynamic light stimuli during retinal development. This study used 80 Sprague-Dawley rats. From eye opening (postnatal day 14), half of the rats were maintained on a daily 12-h light/dark cycle (control group) and the remaining animals were raised under a 12-h strobe light (2 Hz)/dark cycle (strobe light-reared group). Morphological analyses and electroretinogram (ERG) were performed at postnatal weeks 3, 4, 6, 8, and 10. Among retinal neurons, tyrosine hydroxylase-immunoreactive (TH-IR, dopaminergic amacrine cells) cells showed marked plastic changes, such as variations in numbers and soma sizes. In whole-mount preparations at 6, 8, and 10 weeks, type I TH-IR cells showed a decreased number and larger somata, while type II TH-IR cells showed an increased number in strobe-reared animals. Functional assessment by scotopic ERG showed that a-wave and b-wave amplitudes increased at 6 and 8 weeks in strobe-reared animals. These results show that exposure to a strobe light during development causes changes in TH-IR cell number and morphology, leading to a disturbance in normal visual functions.

Global illumination with radiance regression functions

We present radiance regression functions for fast rendering of global illumination in scenes with dynamic local light sources. A radiance regression function (RRF) represents a non-linear mapping from local and contextual attributes of surface points, such as position, viewing direction, and lighting condition, to their indirect illumination values. The RRF is obtained from precomputed shading samples through regression analysis, which determines a function that best fits the shading data. For a given scene, the shading samples are precomputed by an offline renderer. The key idea behind our approach is to exploit the nonlinear coherence of the indirect illumination data to make the RRF both compact and fast to evaluate. We model the RRF as a multilayer acyclic feed-forward neural network, which provides a close functional approximation of the indirect illumination and can be efficiently evaluated at run time. To effectively model scenes with spatially variant material properties, we utilize an augmented set of attributes as input to the neural network RRF to reduce the amount of inference that the network needs to perform. To handle scenes with greater geometric complexity, we partition the input space of the RRF model and represent the subspaces with separate, smaller RRFs that can be evaluated more rapidly. As a result, the RRF model scales well to increasingly complex scene geometry and material variation. Because of its compactness and ease of evaluation, the RRF model enables real-time rendering with full global illumination effects, including changing caustics and multiple-bounce high-frequency glossy interreflections.