gl_TessLevelOuter - contains the outer tessellation levels for the current patch

       Copyright © 2011-2014 Khronos Group

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

       // In tessellation control shaders

       out float gl_TessLevelOuter[4] ;

       // In tessellation evaluation shaders

       in float gl_TessLevelOuter[4] ;

       Available only in the tessellation control and evaluation languages, gl_TessLevelOuter is used to assign
       values to the corresponding outer tesellation levels of the current patch. The values written into
       gl_TessLevelOuter by the tessellation control shader are used by the tessellation primitive generator to
       control primitive tessellation and may be read by the subsequent tessellation evaluation shader.

       As inputs to the tessellation evaluation shader, gl_TessLevelOuter contains the values written by the
       tessellation control shader, if present. If no tessellation control shader is present, it contains the
       default tessellation level.

       gl_TessLevelOuter - contains the outer tessellation levels for the current patch

gl_TessLevelInner(), gl_TessCoord()

       ┌───────────────────┬───────────────────────────────────────────────────────────────────────────────────┐
       │                   │        OpenGLShadingLanguageVersion                                            │
       ├───────────────────┼──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┤
       │ Function          │ 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_TessLevelOuter │  -   │  -   │  -   │  -   │  -   │  -   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │
       └───────────────────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┘