  Point clouds have recently gained interest, especially for real-time
applications and for 3D-scanned material, such as is used in autonomous
driving, architecture, and engineering, to model real estate for renovation or
display. Point clouds are associated with geometry information and attributes
such as color. Be the color unique or direction-dependent (in the case of
plenoptic point clouds), it reflects the colors observed by cameras displaced
around the object. Hence, not only are the viewing references assumed, but the
illumination spectrum and illumination geometry is also implicit. We propose a
model-centric description of the 3D object, that is independent of the
illumination and of the position of the cameras. We want to be able to describe
the objects themselves such that, at a later stage, the rendering of the model
may decide where to place illumination, from which it may calculate the image
viewed by a given camera. We want to be able to describe transparent or
translucid objects, mirrors, fishbowls, fog and smoke. Volumetric clouds may
allow us to describe the air, however ``empty'', and introduce air particles,
in a manner independent of the viewer position. For that, we rely on some
eletromagnetic properties to arrive at seven attributes per voxel that would
describe the material and its color or transparency. Three attributes are for
the transmissivity of each color, three are for the attenuation of each color,
and another attribute is for diffuseness. These attributes give information
about the object to the renderer, with whom lies the decision on how to render
and depict each object.
