Gouraud Shading

Prompt

Identify

You see a 3D computer model with [smooth, gradient-like surfaces] instead of blocky facets. The colors blend seamlessly across the shape.

Principle

Software calculates lighting only at the [corners of a flat polygon¹]. It then [blends these colors evenly] across the surface.

Example

Henri Gouraud: Sylvia's Face (first smooth-shaded 3D facial model), 1971.

Try it out

Look closely at an older 3D video game character. Notice how surfaces seem curved until you spot the straight, jagged outer edges.

Background

In the early days of computer graphics, 3D objects were built from flat triangles or polygons. Early rendering² simply colored each polygon with a single flat shade. This created very blocky, faceted shapes. In 1971, Henri Gouraud invented a faster way to make these faceted objects look smoothly curved. His method calculated the light bouncing off the vertices³, which are the corners of each shape. The computer then smoothly blended those colors across the flat face. This optical trick saved immense computing power. It became a standard hardware feature in 3D graphics cards throughout the 1990s.

Distinction

Flat shading gives every polygon a single solid color. Phong shading calculates light at every single pixel, capturing precise glossy highlights that Gouraud shading misses.

Aftermath

It reveals how clever mathematical approximations can fool the human eye while saving massive amounts of computing power.

Question