Therefore generally the total attenuation formula_8 of a ray at position formula_3, on the projection at angle formula_1, is given by the line integral::formula_11Using the coordinate system of Figure 1, the value of formula_3 onto which the point formula_13 will be projected at angle formula_1 is given by::formula_15So the equation above can be rewritten as:formula_16where formula_17 represents formula_2.