GL_POSITION(3G)

🌸 NAME 🌸

okay bestie, meet gl_Position — contains the position of the current vertex. This page is GL_POSITION(3G) from the [FIXME: manual] manual, and it's literally the main character of vertex output. 💅

---

✨ DECLARATION ✨

so gl_Position is a member of the gl_PerVertex named block:

out gl_PerVertex {
    vec4 gl_Position;
    float gl_PointSize;
    float gl_ClipDistance[];
};

---

🦋 DESCRIPTION 🦋

In the vertex, tessellation evaluation and geometry languages, a single global instance of the gl_PerVertex named block is available, and its gl_Position member is an output that receives the homogeneous vertex position. It may be written at any time during shader execution. The value written to gl_Position will be used by primitive assembly, clipping, culling and other fixed functionality operations, if present, that operate on primitives after vertex processing has occurred. iconic pipeline behaviour, no cap ✨

In the tessellation control language, the gl_PerVertex named block is used to construct an array, gl_out[], whose gl_Position members hold the homogeneous control point position, which become available as inputs to the subsequent tessellation evaluation shader.

The value of gl_Position (or the gl_Position member of the gl_out[] array, in the case of the tessellation control shader) is undefined after the vertex, tessellation control, and tessellation evaluation shading stages if the corresponding shader executable does not write to gl_Position. It is also undefined after the geometry processing stage if the geometry shader executable calls EmitVertex() without having written gl_Position since the last call to EmitVertex() (or hasn't written it at all). 🫶

undefined means undefined, bestie — do not roll the dice on that vibe check 💀

In the tessellation control, tessellation evaluation and geometry languages, the gl_PerVertex named block is used to construct an array, gl_in[] of per-vertex or per-control point inputs whose content represents the corresponding outputs written by the previous stage.

---

🎀 VERSION SUPPORT 🎀

The table vibes are: function name gl_Position, and the OpenGL Shading Language Version column says it's a ✔ in every single one of these versions:

• 1.10
• 1.20
• 1.30
• 1.40
• 1.50
• 3.30
• 4.00
• 4.10
• 4.20
• 4.30
• 4.40
• 4.50

Versions 1.10 to 1.40 - vertex shader only.

Versions 1.50 to 3.30 - vertex and geometry shaders only.

---

🔥 SEE ALSO 🔥

• gl_PointSize()
• gl_ClipDistance()

---

📜 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. http://opencontent.org/openpub/.

---

📜 COPYRIGHT 📜

Copyright © 2011-2014 Khronos Group

---

okay bye bestie 💖 this page is from [FIXME: source], dated 08/09/2021 — GL_POSITION(3G), signing off. 🎀✨