# how to use interpolating functions to smoothly paint a polygon? [duplicate]

consider 4 different colors on the nodes (with different parameter values) how to interpolate when the color values are given on the nodes using the constructed interpolation functions to paint the quadrilateral?

localCoordinates={{-(5/4), -(3/2)}, {3/4, -(3/2)}, {7/4, 7/2}, {-(5/4), -(1/2)}};

deltaNa=((7 + 8 x - 6 y) (-21 + 20 x - 4 y))/(4 (169 + 80 x + 6 y));

deltaNb=-((5 (5 + 4 x) (7 + 8 x - 6 y))/(4 (169 + 80 x + 6 y)));

deltaNc=-((11 (5 + 4 x) (3 + 2 y))/(4 (169 + 80 x + 6 y)));

deltaNd=-((3 (3 + 2 y) (21 - 20 x + 4 y))/(4 (169 + 80 x + 6 y)));


Above are my interpolating functions for each node; A, B, C, D is in the order of local Coordinates.