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# docs.GL

GLSL 4

# gl_TessLevelOuter

## Name

gl_TessLevelOuter — contains the outer tessellation levels for the current patch

## Declaration

    // In tessellation control shaders

`out float gl_TessLevelOuter[4] ;`

    // In tessellation evaluation shaders

`in float gl_TessLevelOuter[4] ;`

## Description

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.

## Version Support

| OpenGL Shading Language Version
--- | ---
Function Name | 1.10 | 1.20 | 1.30 | 1.40 | 1.50 | 3.30 | 4.00 | 4.10 | 4.20 | 4.30 | 4.40 | 4.50
gl_TessLevelOuter | - | - | - | - | - | - | ✔ | ✔ | ✔ | ✔ | ✔ | ✔

## See Also

gl_TessLevelInner, gl_TessCoord

## Copyright

Copyright © 2011-2014 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. https://opencontent.org/openpub/.

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