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 ,
Solid surface wall cladding, because its seamless properties eliminate gaps and crevices that harbor harmful bacteria. Solid surface is manufactured by mixing acrylic, epoxide or polyester resin with powdered bauxite filler and pigments. The material chemically cures and is heated to 60°C or more. Cured material is then cut in sheets or shapes and sanded on one or both sides depending the brand used. Sometimes the material is brought to 160°C and cooled, to improve its heat resistance. Acrylic-modified polyester solid surface can be mixed one sheet at a time using different formulations, effects and appearances. Acrylic-modified polyester solid surface can be