DFI AGP-9710, User Manual, Page: 20 / 20

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AGP-9710 Graphics Card User’s Manual
Shading, Flat
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darkening or lightening the intensity of a polygon
based on the angle between its normal and a vector pointing to a
light source. All pixels on a polygon receive the same adjustment,
resulting in a faceted appearance. The per polygon and per pixel cal-
culation load is very light.
Shading, Gouraud
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darkening or lighting each pixel of a polygon
based on an interpolation between values calculated at the polygon's
vertices. A "vertex normal" is prescribed or inferred, and the intensity
at that vertex is determined by the angle between that normal and a
vector pointing to a light source. Each pixel is interpolated separately,
producing a simulation of a curved surface. Gouraud shading makes
objects appear to have a matte finish, with no specular components.
The per polygon and per pixel calculation load is moderate.
Z Buffer
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a buffer memory that holds the Z (depth) information
per pixel. The Z axis is perpendicular to the X and Y axis of the
screen, and in most practical cases inverse range is uded due to the
fact that it is linear in screen space (where range is not). Compares in
depth between pixels of two polygons can be used to determine
occulting relationships, and only draw the nearer polygon for each
pixel.