GL_FRAGDEPTH(3G)

💅 GL_FRAGDEPTH (3G) 💅

ok so bestie, welcome to the 3G manual page for gl_FragDepth — yes it's a lowercase-gl_ situation, yes that's normal, no we don't ask questions ✨

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🎀 NAME 🎀

gl_FragDepth — the variable that literally sets the depth value for the current fragment. main character energy fr fr 👑

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🌸 DECLARATION 🌸

out float gl_FragDepth ;

that's it. that's the whole declaration. she's simple, she's a float, she's an out variable. obsessed 🫶

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✨ DESCRIPTION ✨

okay so here's the tea, and this part is only available in the fragment language — no vertex shader, no geometry shader, don't even try it 💀

gl_FragDepth is an output variable that you use to establish the depth value for the current fragment. simple as that.

now for the ✨ nuance ✨ (iykyk):

• if depth buffering is enabled and no shader writes to gl_FragDepth, then the fixed function value for depth will be used — that value is contained in the z component of gl_FragCoord()
• otherwise, the value written to gl_FragDepth is used

and now the part where you gotta pay attention bestie, because this is the 💀 gotcha 💀:

If a shader statically assigns to gl_FragDepth, then the value of the fragment's depth may be undefined for executions of the shader that take that path. that is, if the set of linked fragment shaders statically contain a write to gl_FragDepth, then it is responsible for always writing it.

translation: you touched it, it's yours now. you commit to writing that depth on every path, or you get undefined behavior. no halfsies, no take-backs. periodt 💅

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🌈 VERSION SUPPORT 🌈

vibe check on which OpenGL Shading Language versions have gl_FragDepth — she's been an icon in every single one of these, no cap:

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

so yeah, the variable gl_FragDepth is checked off across the entire board 🧚 it ate and left no crumbs

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🦋 SEE ALSO 🦋

• gl_FragCoord() — go read that one too, bestie, they're literally siblings 🫶

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🔥 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 © 2011-2014 Khronos Group

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💖 and that's the whole page!! source: [FIXME: source], dated 08/09/2021, page GL_FRAGDEPTH(3G) — mwah, slay, go write your depth values responsibly 🎀✨🌸