GL_SAMPLEID(3G)

📦
version 1.1 · 7 versions
, in centos-stream 9

💅 GL_SAMPLEID (3G) — the manual, bestie edition ✨

okay so real talk, we're in the 3G manual and the header on this thing literally says GL_SAMPLEID(3G) with a [FIXME: manual] in the middle, so like… that's the vibe we're working with 🫶

🌸 NAME 🌸

gl_SampleID — the variable that holds the index of the sample you're currently processing, no cap 🎀

✨ DECLARATION ✨

in int gl_SampleID ;

💖 DESCRIPTION 💖

So gl_SampleID is a fragment language input variable, and it contains the index of the sample that's currently being processed. Iconic. It lives in the range 0 to gl_NumSamples() - 1, where gl_NumSamples() is the total number of samples in each fragment for the current framebuffer — which means it's 1 if you're rendering to a non-multisample buffer 🦋

⚠️ heads up bestie: any static use of this variable in a fragment shader causes the entire shader to be evaluated per-sample rather than per-fragment. the whole thing. not a drill 😭

When you're rendering to a non-multisample buffer, or if multisample rasterization is disabled, gl_SampleID will always be zero. and just so we're clear — gl_NumSamples() is the sample count of the framebuffer regardless of whether multisample rasterization is enabled or not. two separate things, don't mix them up 💀

🔥 VERSION SUPPORT 🔥

the table energy, but make it a list — this is which OpenGL Shading Language Version numbers actually have gl_SampleID:

  • 1.10 — nope 🙈
  • 1.20 — nope
  • 1.30 — nope
  • 1.40 — nope
  • 1.50 — nope
  • 3.30 — nope
  • 4.00 — ✔️ yes queen 👑
  • 4.10 — ✔️
  • 4.20 — ✔️
  • 4.30 — ✔️
  • 4.40 — ✔️
  • 4.50 — ✔️

so like, 4.00 and up only. everything before that is giving "not invited to the party" 💅

🌈 SEE ALSO 🌈

  • gl_SamplePosition()
  • gl_NumSamples()

go read those too, iykyk 💜

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

okay that's the whole page, bestie! and for the cute sign-off: this one came from [FIXME: source] and it's dated 08/09/2021 — so it's a lil vintage, but she still slays ⭐🌸💖

📦 where this page comes from