How To: Create a Hull Shader
A hull shader is the first of three stages that work together to implement tessellation. The hull-shader outputs drive the tessellator stage, as well as the domain-shader stage. This topic shows how to create a hull shader.
A hull shader transforms a set of input control points (from a vertex shader) into a set of output control points. The number of input and output points can vary in contents and number depending on the transform (a typical transformation would be a basis transformation).
A hull shader also outputs patch constant information, such as tessellation factors, for a domain shader and the tessellator. The fixed-function tessellator stage uses the tessellation factors as well as other state declared in a hull shader to determine how much to tessellate.
To create a hull shader
Design a hull shader. See How To: Design a Hull Shader.
Compile the shader code
Create a hull-shader object using ID3D11Device::CreateHullShader.
HRESULT CreateHullShader( const void *pShaderBytecode, SIZE_T BytecodeLength, ID3D11ClassLinkage *pClassLinkage, ID3D11HullShader **ppHullShader );
Initialize the pipeline stage using ID3D11DeviceContext::HSSetShader.
void HSSetShader( ID3D11HullShader *pHullShader, ID3D11ClassInstance *const *ppClassInstances, UINT NumClassInstances );
A domain shader must be bound to the pipeline if a hull shader is bound. In particular, it is not valid to directly stream out hull shader control points with the geometry shader.