gouraud shading
Gouraud shading is one of the shading techniques for rendering three-dimensional bodies with curved surfaces. In this method, the polygon edges that are visible in flat shading are smoothed to such an extent that they are no longer visible.
For this purpose, in Gouraud shading, the colors of the vertices of each individual polygon are interpolated and the shading is calculated via this linear interpolation of the polygon edges and scanlines. Each individual polygon has in itself a color gradient determined by the edge values of the adjacent polygons.
Gouraud shading is suitable for the representation of complex bodies with curved surfaces and shows realistic, edge-free color gradients. The color gradient is approximated on the polygonal surface of the curved surface.
The disadvantage of this shading method is that the gradient can only sufficiently contour surfaces that are irregularly strongly curved if the polygons are made smaller.
Gouraud shading is the standard method used by graphics cards.