GLDRAWARRAYSINDIRECT(3G)

💅 GLDRAWARRAYSINDIRECT(3G) ✨

okay bestie, welcome to the manual page for glDrawArraysIndirect — that's the one from the [FIXME: manual] bind-up, yes that's genuinely the manual name, we don't ask questions around here 🫶. Sit down, hydrate, and let's get into it, because this one is lowkey iconic.

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🌸 NAME 🌸

glDrawArraysIndirect — render primitives from array data, taking parameters from memory. fr fr, the parameters come from memory, not from your cute lil function arguments. main character energy.

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✨ C SPECIFICATION ✨

void glDrawArraysIndirect(GLenum mode, const void *indirect);

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🎀 PARAMETERS 🎀

• mode — tells the GPU what kind of primitives to render. Accepts the symbolic constants GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES, GL_LINE_STRIP_ADJACENCY, GL_LINES_ADJACENCY, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, GL_TRIANGLES, GL_TRIANGLE_STRIP_ADJACENCY, GL_TRIANGLES_ADJACENCY, and GL_PATCHES. yes bestie, all of them, we're not playing 💅
• indirect — the address of a structure that holds all the draw parameters. it's giving "here's where the actual info lives."

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🦋 DESCRIPTION 🦋

glDrawArraysIndirect specifies multiple geometric primitives with very few subroutine calls. very demure, very mindful, extremely efficient. 🌈

It behaves similarly to glDrawArraysInstancedBaseInstance(), except that the parameters to glDrawArraysInstancedBaseInstance() are stored in memory at the address given by indirect. so instead of passing like eight things, you pass one pointer. slay.

The parameters addressed by indirect are packed into a structure that takes this exact form (in C):

typedef  struct {
    uint  count;
    uint  primCount;
    uint  first;
    uint  baseInstance;
} DrawArraysIndirectCommand;

const DrawArraysIndirectCommand *cmd = (const DrawArraysIndirectCommand *)indirect;
glDrawArraysInstancedBaseInstance(mode, cmd->first, cmd->count, cmd->primCount, cmd->baseInstance);

copy that verbatim pls, it's load-bearing 🧚

If a buffer is bound to the GL_DRAW_INDIRECT_BUFFER binding at the time of a call to glDrawArraysIndirect, then indirect is interpreted as an offset, in basic machine units, into that buffer — and the parameter data is read from the buffer rather than from client memory. iykyk. 🔥

In contrast to glDrawArraysInstancedBaseInstance(), the first member of the parameter structure is unsigned, and out-of-range indices do not generate an error. no error, no drama, we simply proceed.

⚠️ Vertex attributes that are modified by glDrawArraysIndirect have an unspecified value after glDrawArraysIndirect returns. that's the undefined-ish part, bestie, don't touch them and expect a vibe. Attributes that aren't modified remain well defined. 👑

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💜 NOTES 💜

• The baseInstance member of the DrawArraysIndirectCommand structure is defined only if the GL version is 4.2 or greater.
• For versions of the GL less than 4.2, this parameter is present but is reserved and should be set to zero.
• On earlier versions of the GL, behavior is undefined if it is non-zero. so like… don't. 💀

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🍓 ERRORS 🍓

• GL_INVALID_ENUM is generated if mode is not an accepted value.
• GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to an enabled array or to the GL_DRAW_INDIRECT_BUFFER binding and the buffer object's data store is currently mapped.
• GL_INVALID_OPERATION is generated if a geometry shader is active and mode is incompatible with the input primitive type of the geometry shader in the currently installed program object.
• GL_INVALID_OPERATION is generated if mode is GL_PATCHES and no tessellation control shader is active.

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🌟 VERSION SUPPORT 🌟

so the original has a whole big table for this, and we're gonna give it to you straight as a list, because tables are not the moment. columns were: the function/feature name, then OpenGL versions 2.0, 2.1, 3.0, 3.1, 3.2, 3.3, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5.

row for glDrawArraysIndirect:

• OpenGL 2.0 — - 🙈
• OpenGL 2.1 — - 🙈
• OpenGL 3.0 — - 🙈
• OpenGL 3.1 — - 🙈
• OpenGL 3.2 — - 🙈
• OpenGL 3.3 — - 🙈
• OpenGL 4.0 — ✔ 🔥
• OpenGL 4.1 — ✔ 🔥
• OpenGL 4.2 — ✔ 🔥
• OpenGL 4.3 — ✔ 🔥
• OpenGL 4.4 — ✔ 🔥
• OpenGL 4.5 — ✔ 🔥

so basically: 4.0 and up, periodt. 👑

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🌈 SEE ALSO 🌈

glDrawArrays(), glDrawArraysInstanced(), glDrawElements(), glDrawRangeElements() — go read those too bestie, they're the supporting cast. 🦋

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💖 COPYRIGHT 💖

Copyright © 2010-2014 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 © 2010-2014 Khronos Group.

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okay that's the whole thing, you ate that 🫶✨ mwah. this little love letter was brought to you by [FIXME: source], dated 08/09/2021, and it signs off as GLDRAWARRAYSINDIRECT(3G) — go forth and draw them arrays indirectly, icon. 💅🎀