How To: Instance a Geometry Shader

Geometry shader instancing allows multiple executions of the same geometry shader to be executed per primitive. To instance a geometry shader, add an instance attribute to the main shader function and identify an instance index parameter in the shader function body.

To Instance a Geometry Shader:

1. Add the instance attribute to the main function.

   [instance(24)]
   

   This defines the number of instances (a maximum of 32) to be run for each primitive.

2. Attach the SV_GSInstanceID system value to a variable in the function parameter list that can be used to track the ID of the instance being executed.

   uint InstanceID : SV_GSInstanceID
   

3. Compile and create the shader just as you would any other geometry shader.

Other details include:

• The maximum instance count is 32.
• The maximum vertex count is a per-instance maximum vertex count.
• Each instance invocation (like any geometry shader invocation) increases the invocation count and generates an implicit RestartStrip().

Related topics

Geometry Shader Features