Geometry shaders can be invoked more than one time for each input
primitive.
This is known as geometry shader instancing and is requested by including
an OpExecutionMode
instruction with mode
specified as
Invocations
and the number of invocations specified as an integer
literal.
In this mode, the geometry shader will execute n times for each input
primitive, where n is the number of invocations specified in the
OpExecutionMode
instruction.
The instance number is available to each invocation as a built-in input
using InvocationId
.