Calculates the Bernsteincoefficient of degree and index id at the value t. This is used in the calculation of Bezierfunction and Meshes
value of the Bernsteincoefficient
if A, B, C, D are Points of type xy respectivly xyz then b(t) = A * Bernstein(3, 0) + B * Bernstein(3, 1) + C*Bernstein(3, 2) + D * Bernstein(3, 3) results the interpolated Beziervalue of degree 3. "*" means a multiplication between a Point ( xy or xyz ) and a double value.