Gouraud shading
When Gouraud shading (sometimes Gouraud shading ) is a shading method in 3D computer graphics to polygonal surfaces to fill. It was named after its developer Henri Gouraud , who first introduced it in 1971.
Procedure
When Gouraud shading, the parameters for the color calculation at the vertices (are first vertices are required) determined. These include, for example, the normal vector , light direction vector or the camera direction vector. These parameters are used to calculate the color value of the vertex (this step is comparable to the Phong lighting model , but the color values are only calculated per vertex and not per fragment). During rasterization, the color value within the polygon is then interpolated in 3D space for each fragment to be generated (e.g. using barycentric coordinates ).
Due to the interpolation, faceted surfaces of a displayed object do not appear angular as with flat shading , but rather soft. The silhouette of the object, however, remains angular. Gouraud shading is one of the fastest processes in 3D computer graphics for representing spatial objects. If non-diffuse areas with relatively large polygons are to be displayed, the more complex Phong shading must be used, since with Gouraud shading highlights can be lost if they were located within a polygon.
Disadvantages of this type of interpolation are jumps in the color gradient, Mach stripes and the appearance of the moiré effect .
Polygon rendered with Gouraud shading
Sphere rendered with Gouraud shading with inaccuracies on the polygon sides
A still image of the same sphere represented by a larger number of polygons
