37-Issue 7

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/2632664

Browse

Browsing 37-Issue 7 by Subject "centered computing"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Directing the Photography: Combining Cinematic Rules, Indirect Light Controls and Lighting-by-Example
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Galvane, Quentin; Lino, Christophe; Christie, Marc; Cozot, Rémi; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    The placement of lights in a 3D scene is a technical and artistic task that requires time and trained skills. Most 3D modelling tools only provide a direct control of light sources, through the manipulation of parameters such as size, location, flux (the perceived power of light) or opening angle (the light frustum). Approaches have been relying on automated or semi-automated techniques to relieve users from such low-level manipulations at the expense of an important computational cost. In this paper, guided by discussions with experts in scene and object lighting, we propose an indirect control of area light sources. We first formalize the classical 3-point lighting design principle (key-light, fill-lights and back/rim-lights) in a parametric model. Given a key-light placed in the scene, we then provide a computational approach to (i) automatically compute the position and size of fill-lights and back/rim-lights by analyzing the geometry of 3D character, and (ii) automatically compute the flux and size of key, fill and back/rim lights, given a sample reference image in a computationally efficient way. Results demonstrate the benefits of the approach on the quick lighting of 3D characters, and further demonstrate the feasibility of interactive control of multiple lights through image features.
  • No Thumbnail Available
    Item
    Learning Scene Illumination by Pairwise Photos from Rear and Front Mobile Cameras
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Cheng, Dachuan; Shi, Jian; Chen, Yanyun; Deng, Xiaoming; Zhang, Xiaopeng; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    Illumination estimation is an essential problem in computer vision, graphics and augmented reality. In this paper, we propose a learning based method to recover low-frequency scene illumination represented as spherical harmonic (SH) functions by pairwise photos from rear and front cameras on mobile devices. An end-to-end deep convolutional neural network (CNN) structure is designed to process images on symmetric views and predict SH coefficients. We introduce a novel Render Loss to improve the rendering quality of the predicted illumination. A high quality high dynamic range (HDR) panoramic image dataset was developed for training and evaluation. Experiments show that our model produces visually and quantitatively superior results compared to the state-of-the-arts. Moreover, our method is practical for mobile-based applications.
  • No Thumbnail Available
    Item
    A New Uniform Format for 360 VR Videos
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Guo, Juan; Pei, Qikai K.; Ma, Guilong L.; Liu, Li; Zhang, Xinyu Y.; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    Recent breakthroughs in VR technologies, especially in economic VR headsets and massive smartphones are creating a fastgrowing demand for 3D immersive VR content. 360 VR videos record a surrounding environment in every direction and give users a fully immersive experience. Thanks to a ton of 360 cameras that launched in the past years, 360 video content creation is exploding and 360 VR videos are becoming a new video standard in the digital industry. When ERP and CMP are perhaps the most prevalent projection and packing layout for storing 360 VR videos, they have severe projection distortion, internal discontinuous seams or disadvantages in aspect ratio. We introduce a new format for packing and storing 360 VR videos using two stage mappings. Hemispheres are seamlessly and uniformly mapped onto squares. Two respective squares are stitched to form a rectangle with the aspect ratio 2 : 1. Our approach is able to avoid internal discontinuity and generate uniform pixel distribution, while keeping the aspect ratio close to the majority standard aspect ratio of 16 : 9.