Position
Position
Decorating a variable with the Position built-in decoration will make
that variable contain the position of the current vertex.
In the last pre-rasterization
shader stage, the value of the variable decorated with Position is
used in subsequent primitive assembly, clipping, and rasterization
operations.
When Position decorates a variable in the Input Storage Class, it
contains the data written to the output variable decorated with
Position from the previous shader stage.
Valid Usage
VUID-Position-Position-04318
The Position decoration must be used only within the MeshEXT,
MeshNV, Vertex, TessellationControl,
TessellationEvaluation, or Geometry Execution Model
VUID-Position-Position-04319
The variable decorated with Position within the MeshEXT,
MeshNV, or Vertex Execution Model must be declared using the
Output Storage Class
VUID-Position-Position-04320
The variable decorated with Position within the
TessellationControl, TessellationEvaluation, or Geometry
Execution Model must not be declared using a Storage Class other than
Input or Output
VUID-Position-Position-04321
The variable decorated with Position must be declared as a
four-component vector of 32-bit floating-point values