Illuminating image-based objects

We present a new scheme of data representation for image-based objects. It allows the illumination to be changed interactively without knowing any geometrical information (e.g. depth or surface normal) of the scene, but the resulting images are physically correct. The scene is first sampled from different view points and under different illuminations. By treating each pixel on the image plane as a surface element, the sampled images are used to measure the apparent BRDF of each surface element. Two compression schemes, spherical harmonics and discrete cosine transform, are proposed to compress the tabular BRDF data. Whenever the user changes the illumination a certain number of views are reconstructed. The correct user perspective view is then displayed using the standard texture mapping hardware. Hence, the intensity, the type and the number of the light sources can be manipulated interactively.