The Rendering Pipeline - Practical Rendering and Computation with Direct3D 11 - page 163

Figure 3.22. Artifacts from linear rasterization when used in projections that don't preserve lines.
control points of a control patch (such as a complete patch normal vector or a screen-space
derivative of the patch position) can be calculated once and used many times later. Once
again, this reduces the number of computations required to perform a calculation.
3.5.4 Hull Shader Pipeline Output
We have already seen that the results of executing the hull shader program are the output
control points of the control patch to be used in tessellation. These control points are its
primary way to pass information down the pipeline. Ultimately, these control points will
be consumed by the domain shader stage, where they will be used to generate positions
for each of the newly tessellated points from the tessellator stage. Requirements for the
attributes of the output of the hull shader are very flexible. There are no mandatory system
values that need to be written. Instead, it is up to the developer to supply the information
needed for processing in later stages. But although the output requirements are very flex-
ible, some common attributes are usually included. The positions of the control points are