gl_InvocationID - contains the invocation index of the current shader

       Copyright © 2011-2014 Khronos Group

[FIXME: source]                                    11/18/2024                                GL_INVOCATIONID(3G)

       in int gl_InvocationID ;.SH "DESCRIPTION"

       In the tessellation control language, gl_InvocationID contains the index of the output patch vertex
       assigned to the shader invocation. It is assigned an integer value in the range [0, N-1] where N is the
       number of output patch vertices.

       In the geometry language, gl_InvocationID identifies the invocation number assigned to the geometry
       shader invocation. It is assigned an integer value in the range [0, N-1] where N is the number of
       geometry shader invocations per primitive.

       gl_InvocationID - contains the invocation index of the current shader

gl_InstanceID()

       ┌─────────────────┬───────────────────────────────────────────────────────────────────────────────────┐
       │                 │        OpenGLShadingLanguageVersion                                            │
       ├─────────────────┼──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┤
       │ Variable        │ 1.10 │ 1.20 │ 1.30 │ 1.40 │ 1.50 │ 3.30 │ 4.00 │ 4.10 │ 4.20 │ 4.30 │ 4.40 │ 4.50 │
       │ Name            │      │      │      │      │      │      │      │      │      │      │      │      │
       ├─────────────────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┤
       │ gl_InvocationID │  -   │  -   │  -   │  -   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │
       └─────────────────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┘

       [1] Versions 1.50 to 3.30 - geometry shaders only.