Interactive lighting manipulation application on GPU

IEEE Transactions on Visualization and Computer Graphics, 2000

Computer augmented reality (CAR) is a rapidly emerging field which enables users to mix real and virtual worlds. Our goal is to provide interactive tools to perform common illumination, i.e., light interactions between real and virtual objects, including shadows and relighting (real and virtual light source modification). In particular, we concentrate on virtually modifying real light source intensities and inserting virtual lights and objects into a real scene; such changes can be very useful for virtual lighting design and prototyping. To achieve this, we present a three-step method. We first reconstruct a simplified representation of real scene geometry using semi-automatic vision-based techniques. With the simplified geometry, and by adapting recent hierarchical radiosity algorithms, we construct an approximation of real scene light exchanges. We next perform a preprocessing step, based on the radiosity system, to create unoccluded illumination textures. These replace the original scene textures which contained real light effects such as shadows from real lights. This texture is then modulated by a ratio of the radiosity (which can be changed) over a display factor which corresponds to the radiosity for which occlusion has been ignored. Since our goal is to achieve a convincing relighting effect, rather than an accurate solution, we present a heuristic correction process which results in visually plausible renderings. Finally, we perform an interactive process to compute new illumination with modified real and virtual light intensities. Our results show that we are able to virtually relight real scenes interactively, including modifications and additions of virtual light sources and objects.

Eurographics, 1999

Thème 3 -Interaction homme-machine, images, données, connaissances Projet iMAGIS Rapport technique n˚0230 -Avril 1999 -16 pages Abstract: Lighting design is tedious due to the required physical manipulation of real light sources and objects. As an alternative, we present an interactive system to virtually modify the lighting and geometry of scenes with both real and synthetic objects, including mixed real/virtual lighting and shadows. In our method real scene geometry is first approximatively reconstructed from photographs. Additional images are taken with a real light in different positions from the same viewpoint to estimate reflectance. A filtering process is used to compensate for modeling errors, and per image reflectances are averaged to generate an approximate reflectance image for the given viewpoint, removing shadows in the process. This estimate is used to initialise a global illumination hierarchical radiosity system, representing real-world secondary illumination; the system is optimized for interactive updates. Direct illumination from lights is calculated separately using ray-casting and a table for efficient reuse where appropriate.

2009

We propose a novel rendering method which supports interactive BRDF editing as well as relighting on a 3D scene. For interactive BRDF editing, we linearize an analytic BRDF model with basis BRDFs obtained from a principal component analysis. For each basis BRDF, the radiance transfer is precomputed and stored in vector form. In rendering time, illumination of a point is computed by multiplying the radiance transfer vectors of the basis BRDFs by the incoming radiance from gather samples and then linearly combining the results weighted by user-controlled parameters. To improve the level of accuracy, a set of sub-area samples associated with a gather sample refines the glossy reflection of the geometric details without increasing the precomputation time. We demonstrate this program with a number of examples to verify the real-time performance of relighting and BRDF editing on 3D scenes with complex lighting and geometry. Categories and Subject Descriptors (according to ACM CCS): Computer Graphics [I.3.3]: Three-Dimensional Graphics and Realism-For enhanced accuracy of the glossy reflection, we employ a level-of-detail approach with sub-area samples. As in the direct-to-indirect light transfer by Hasan et al. [HPB06], our algorithm gathers radiance from pre-sampled surface points to compute the illumination of a pixel. The surface points are termed gather samples. This approach, how-

GPU-based interactive global illumination techniques are receiving an increasing interest from both the research and the industrial community as real-time graphics applications strive for visually rich and realistic dynamic three-dimensional environments. This paper presents a fast new diffuse global illumination method that generates a sparse set of low-cost radiance field evaluation points (radiance hints) and computes an arbitrary number of diffuse inter-reflections within a given volume. The proposed approximate technique combines ideas from exiting grid-based radiance caching techniques with reflective shadow maps as well as a stochastic scheme for visibility calculations, in order to achieve high frame rates for multiple light bounces.

Eurographics, 1997

A new image-based rendering method, based on the light field and Lumigraph system, allows illumination to be changed interactively. It does not try to recover or use any geometrical information (e.g., depth or surface normals) to calculate the illumination, but the resulting images are physically correct. The scene is first sampled from different viewpoints and under different illuminations. Treating each pixel on the back plane of the light slab as a surface element, the sampled images are used to find an apparent BRDF of each surface element. The tabular BRDF data of each pixel is further transformed to the spherical harmonic domain for efficient storage. Whenever the user changes the illumination setting, a certain number of views are reconstructed. The correct user perspective view is then displayed using the texture mapping technique of the Lumigraph system. Hence, the intensity, the type and the number of the light sources can be manipulated interactively.

Current relighting applications often constrain one or several factors of the rendering equation to keep the rendering speed real-time. For example, visibility is often precalculated and animations are not allowed, changes in lighting are limited to simple rotation or the lighting is not very detailed. Other techniques compromise on quality and often coarsely tabulate BRDF functions. In order to solve these problems, some techniques have started to use spherical radial basis functions. However, solving the triple product integral does not guarantee interactivity. In order to dynamically change lighting conditions or alter scene geometry and materials, these three factors need to be converted to the SRBF representation in a fast manner. This paper presents a method to perform the SRBF data construction and rendering in real-time. To support dynamic high-frequency lighting, a multiscale residual transformation algorithm is applied. Area lights are detected through a peak detection alg...

2003

Abstract Interactive visualization of complex, real-world light sources has so far not been feasible. We present a hardware accelerated direct lighting algorithm based on a recent high quality light source acquisition technique. By introducing an approximate reconstruction of the exact model, a multi-pass rendering approach, and a compact data representation, we are able to achieve interactive frame rates. The method is part of the processing pipeline from light source acquisition to high quality lighting of a virtual world.

ACM Transactions on Graphics, 2007

We present a technique for interactive relighting in which source radiance, viewing direction, and BRDFs can all be changed on the fly. In handling dynamic BRDFs, our method efficiently accounts for the effects of BRDF modification on the reflectance and incident radiance at a surface point. For reflectance, we develop a BRDF tensor representation that can be factorized into adjustable terms for lighting, viewing, and BRDF parameters. For incident radiance, there exists a non-linear relationship between indirect lighting and BRDFs in a scene, which makes linear light transport frameworks such as PRT unsuitable. To overcome this problem, we introduce precomputed transfer tensors (PTTs) which decompose indirect lighting into precomputable components that are each a function of BRDFs in the scene, and can be rapidly combined at run time to correctly determine incident radiance. We additionally describe a method for efficient handling of high-frequency specular reflections by separating...

ACM Transactions on Graphics, 2007

: Left: An office which receives light through a window on the right wall while the rest of the scene is lit indirectly. Our method avoids explicit visibility computation and our GPU implementation enables the manipulation of the light or objects at 9 frames per second (fps). This includes four iterations of radiance and antiradiance per frame. Center: We can also include an animated character; indirect light is updated at 7.8 fps. Right: Our method naturally handles glossy surfaces; the glossy bust is lit indirectly, since the light points at the ceiling.

The Journal of Visualization and Computer Animation, 1998

A new data representation of image-based objects is presented. With this representation, the user can change the illumination as well as the viewpoint of an image-based scene. Physically correct imagery can be generated without knowing any geometrical information (e.g. depth or surface normal) of the scene. By treating each pixel on the image plane as a surface element, we can measure its apparent BRDF (bidirectional reflectance distribution function) by collecting information in the sampled images. These BRDFs allow us to calculate the correct pixel colour under a new illumination set-up by fitting the intensity, direction and number of the light sources. We demonstrate that the proposed representation allows re-rendering of the scene illuminated by different types of light sources. Moreover, two compression schemes, spherical harmonics and discrete cosine transform, are proposed to compress the huge amount of tabular BRDF data.