gl_SampleID — contains the index of the sample currently being processed
in int gl_SampleID ; gl_SampleID is a fragment language input variable that contains the index of the sample currently being processed. This variable is in the range 0 to gl_NumSamples - 1, where gl_NumSamples is the total number of samples in each fragment for the current framebuffer (and thus 1 if rendering to a non-multisample buffer). Any static use of this variable in a fragment shader causes the entire shader to be evaluated per-sample rather than per-fragment.
When rendering to a non-multisample buffer, or if multisample rasterization is disabled, gl_SampleID will always be zero. gl_NumSamples is the sample count of the framebuffer regardless of whether multisample rasterization is enabled or not.
| OpenGL Shading Language Version | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Variable 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_SampleID | - | - | - | - | - | - | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
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