Solid angle to the unit sphere with center P, which can be calculated as the surface integral: where formula_5 is the unit vector corresponding to formula_6, the position vector of an infinitesimal area of surface with respect to point P, and where formula_7 represents the unit normal vector to . Even if the projection on the unit sphere to the surface S is not isomorphic, the multiple folds are correctly considered according to the surface orientation described by the sign of the scalar product formula_8. Thus one can approximate the solid angle subtended by a small facet having flat surface area ,
Volume solid Volume solid Volume solid is the volume of paint after it has dried. Paint contains solvent, resin, pigments and additives. After applying the paint, the solid portion will be left on the substrate. Volume solid is the term which indicates the proportion of the solid contacting the paint on a volume basis. For example, if paint is applied in a wet film at a 100 µm thickness, and the volume solid of paint is 50%, then the dry film thickness will be 50 µm as 50% of the wet paint has evaporated. Suppose the volume solid is 100%, and the