Gouraud shading

Gouraud shading is a technique used in computer graphics to create smooth, realistic shading on 3D objects. Unlike flat shading, which colors each face of an object with a single tone, Gouraud shading interpolates colors across the faces. This is achieved by assigning a color to each edge of the object, factoring in lighting, and then calculating intermediate colors to produce a smooth gradient. This method significantly enhances the visual realism of rendered images and is capable of real-time rendering in modern systems.1

Gouache, on the other hand, is a painting technique that uses opaque pigments mixed with gum. It creates a distinct, brilliant surface layer on paper, differing from transparent watercolors. Gouache has ancient origins and was used by artists like François Boucher.2