The Tessellation Pipeline - Practical Rendering and Computation with Direct3D 11 - page 264

Despite these immediately obvious savings in storage and bandwidth, it is important
to note the trade-off. Functions that define higher-order surfaces must be sampled in real
time and cannot be precalculated. These functions can be mathematically complex and
require non-trivial processing time by the GPU. On the whole, GPU tessellation pays for
itself, but it doesn't come for free.
Higher-order surfaces have been a common tool in content creation packages for
decades and are well understand by any experienced artist. Previously, artists had to work
only with triangle-based meshes, which complicated their workflow by requiring them to
participate in the implementation details, as opposed to the purely artistic and conceptual.
Tessellation is therefore useful in both technical and artistic contexts. These advan-
tages indirectly also benefit businesses, by reducing the amount of time and effort required.
A technical solution that uses resources more conservatively and scales well across
different GPUs can allow for less complex code, having a single code path that can be ap-
plied to many configurations. One historical difficulty with real-time graphics has been the
common need for many code paths to be implemented and fine tuned for each major hard-
ware configuration, which quickly becomes a maintenance and development nightmare.
Cleaner development can only be a good thing.
Enabling artists to be more productive greatly reduces the time needed to produce
high-quality art assets. Regarding content creation, it has been noted that the drive for
higher-quality real-time graphics has put more strain on art production than it has software.
Direct3D 11 helps balance this.
4.1.3 History of Tessellation
Curved surfaces and tessellation algorithms are not new concepts. Traditionally, they have
only been available to offline rendering, since their complexity was prohibitively high for
real-time applications. A well-known example is films using computer-generated imagery
(CGI) from Pixar (such as Toy Story) and DreamWorks (such as Shrek). Outside of media,
design and engineering were common early applications of this style of mathematics and
rendering. In 1962 Pierre Bezier popularized Paul de Casteljau's work on what has become
known as a Bezier curve (or Bezier surface) while working on car designs for Renault.
The advantages of using mathematical curves for design became immediately obvious, for
many of the reasons discussed above.
Over the decades, various tools, often for computer-aided design (CAD), were de-
veloped to allow manipulation of higher-order surfaces. For higher-order surfaces to be
combined with real-time rendering, as in the early days of commodity three-dimensional
computer games, it was necessary to "bake" the mathematical surface into a fixed triangle
equivalent that could be used by the rendering software and hardware of the day. This made
it impossible to scale the quality and resolution of surfaces, since the required information
had been lost.