Neural radiance fields (NeRFs) enable novel-view synthesis with unprecedented visual quality. However, to render photorealistic images, NeRFs require hundreds of deep multilayer perceptron (MLP) evaluations - for each pixel. This is prohibitively expensive and makes realtime rendering infeasible, even on powerful modern GPUs. In this paper, we propose a novel approach to distill and bake NeRFs into highly efficient mesh-based neural representations that are fully compatible with the massively parallel graphics rendering pipeline. We represent scenes as neural radiance features encoded on a two-layer duplex mesh, which effectively over-comes the inherent inaccuracies in 3D surface reconstruction by learning the aggregated radiance information from a reliable interval of ray-surface intersections. To exploit local geometric relationships of nearby pixels, we leverage screen-space convolutions instead of the MLPs used in NeRFs to achieve high-quality appearance. Finally, the performance of the whole framework is further boosted by a novel multi-view distillation optimization strategy. We demonstrate the effectiveness and superiority of our approach via extensive experiments on a range of standard datasets.

Computational imaging has always benefited from tools that modulate light along the many dimensions of its plenoptic function. This paper provides a practical architecture for achieving spatially varying spectral modulation using a liquid crystal phase spatial light modulator (SLM). The use of a phase SLM, however, results in strong optical aberrations due to the unintended phase modulation, thereby precluding spectral modulation at high spatial resolutions. To mitigate this, we provide a careful and systematic analysis of the aberrations arising out of phase SLMs for the purpose of spatially varying spectral modulation; this analysis results in a dual strategy of “good patterns” that minimize the optical aberrations and a deep restoration network that overcomes any residual aberrations. We show a number of unique operating points with our prototype including single- and multi-image hyperspectral imaging, material classification (fewer than two images), and dynamic spectral filtering at video rates.

We address the problem of camera motion estimation from a single blurred image with the aid of deep convolutional neural networks. Unlike learning-based prior works that estimate a space-invariant blur kernel, we solve for the global camera motion which in turn represents the space-variant blur at each pixel. Leveraging the camera motion as well as the clean reference image during training, we resort to a semi -supervised training scheme that utilizes the strengths of both supervised and unsupervised learning to solve for the camera motion undergone by a space-variant blurred image. Finally, we show the effectiveness of such a motion estimation network with applications in space-variant deblurring and change detection.

Row-wise exposure delay present in CMOS cameras is responsible for skew and curvature distortions known as the rolling shutter (RS) effect while imaging under camera motion. Existing RS correction methods resort to using multiple images or tailor scene-specific correction schemes. We propose a convolutional neural network (CNN) architecture that automatically learns essential scene features from a single RS image to estimate the row-wise camera motion and undo RS distortions back to the time of first-row exposure. We employ long rectangular kernels to specifically learn the effects produced by the row-wise exposure. Experiments reveal that our proposed architecture performs better than the conventional CNN employing square kernels. Our single-image correction method fares well even operating in a frame-by-frame manner against video-based methods and performs better than scene-specific correction schemes even under challenging situations.

In this paper, we address the problem of registering a distorted image and a reference image of the same scene by estimating the camera motion that had caused the distortion. We simultaneously detect the regions of changes between the two images. We attend to the coalesced effect of rolling shutter and motion blur that occurs frequently in moving CMOS cameras. We first model a general image formation framework for a 3D scene following a layered approach in the presence of rolling shutter and motion blur. We then develop an algorithm which performs layered registration to detect changes. This algorithm includes an optimisation problem that leverages the sparsity of the camera trajectory in the pose space and the sparsity of changes in the spatial domain. We create a synthetic dataset for change detection in the presence of motion blur and rolling shutter effect covering different types of camera motion for both planar and 3D scenes. We compare our method with existing registration methods and also show several real examples captured with CMOS cameras.

The rule of perspectivity that 'straight-lines-mustremain-straight' is easily inflected in CMOS cameras by distortions introduced by motion. Lines can be rendered as curves due to the row-wise exposure mechanism known as rolling shutter (RS). We solve the problem of correcting distortions arising from handheld cameras due to RS effect from a single image free from motion blur with special relevance to urban scenes. We develop a procedure to extract prominent curves from the RS image since this is essential for deciphering the varying row-wise motion. We pose an optimization problem with line desirability costs based on straightness, angle, and length, to resolve the geometric ambiguities while estimating the camera motion based on a rotation-only model assuming known camera intrinsic matrix. Finally, we rectify the RS image based on the estimated camera trajectory using inverse mapping. We show rectification results for RS images captured using mobile phone cameras. We also compare our single image method against existing video and nonblind RS rectification methods that typically require multiple images.

Capturing multiple images using the burst mode of handheld cameras can be a boon to obtain a high resolution (HR) image by exploiting the subpixel motion among the captured images arising from handshake. However, the caveat with mobile phone cameras is that they produce rolling shutter (RS) distortions that must be accounted for in the super-resolution process. We propose a method in which we obtain an RS-free HR image using HR camera trajectory estimated by leveraging the intra- and inter-frame continuity of the camera motion. Experimental evaluations demonstrate that our approach can effectively recover a super-resolved image free from RS artifacts.

Classical multi-image super-resolution (SR) algorithms, designed for CCD cameras, assume that the motion among the images is global. But CMOS sensors that have increasingly started to replace their more expensive CCD counterparts in many applications do not respect this assumption if there is a motion of the camera relative to the scene during the exposure duration of an image because of the row-wise acquisition mechanism. In this paper, we study the hitherto unexplored topic of multi-image SR in CMOS cameras. We initially develop an SR observation model that accounts for the row-wise distortions called the "rolling shutter" (RS) effect observed in images captured using non-stationary CMOS cameras. We then propose a unified RS-SR framework to obtain an RS-free high-resolution image (and the row-wise motion) from distorted low-resolution images. We demonstrate the efficacy of the proposed scheme using synthetic data as well as real images captured using a hand-held CMOS camera. Quantitative and qualitative assessments reveal that our method significantly advances the state-of-the-art.

Temporal artifacts due to sequential acquisition of measurements in compressed sensing manifest differently from a conventional optical camera. We propose a framework for dynamic scenes to estimate the relative global motion between camera and scene from measurements acquired using a compressed sensing camera. We follow an adaptive block approach where the resolution of the estimated motion path depends on the motion trajectory. To underline the importance of the proposed motion estimation framework, we develop a face recognition algorithm in the compressive sensing domain by factoring in the time-varying nature of the acquisition process.