This paper presents a new multispectral compact laboratory gonioreflectometer that can adequately sample bidirectional reflectance functions. It will be used for obtaining BRDF data of vegetation elements that can be applied in light transport simulations within virtual forests. In this way, future investigation and interpretation of radiation of forest canopies will be made possible.

We present an image-based technique to relight real objects illuminated by a 4D incident light field, representing the illumination of an environment. By exploiting the richness in angular and spatial variation of the light field, objects can be relit with a high degree of realism.We record photographs of an object, illuminated from various positions and directions, using a projector mounted on a gantry as a moving light source. The resulting basis images are used to create a subset of the full reflectance field of the object. Using this reflectance field, we can create an image of the object, relit with any incident light field and observed from a flxed camera position.To maintain acceptable recording times and reduce the amount of data, we propose an efficient data acquisition method.Since the object can be relit with a 4D incident light field, illumination effects encoded in the light field, such as shafts of shadow or spot light effects, can be realized.

In multipass rendering, care has to be taken to include all light transport only once in the final solution. Therefore the different methods in current multipass configurations handle a perfectly disjunct part of the light transport. In this paper a Monte Carlo variance reduction technique is presented that probabilistically weights overlapping transport between different methods. A good heuristic for the weights is derived so that strengths of the respective methods are retained. The technique is applied to a combination of radiosity and bidirectional path tracing and significant improvement is obtained over the non‐weighted combination. This method promises to be a very useful extension to other multipass algorithms as well.

Abstract In this paper we introduce the concept of the global reflection distribution function which allows concise formulation of the global illumination problem. Unlike previous formulations it is not geared towards any specific algorithm. As an example of its versatility we derive a Monte Carlo rendering algorithm that seamlessly integrates the ideas of shooting and gathering power to create photorealistic images.