GLDRAWARRAYSINSTANCE(3G)

GLDRAWARRAYSINSTANCE ✨💅 (from the 3G manual, bestie)

okay so this is the GLDRAWARRAYSINSTANCE page from the 3G manual, and the header has a little [FIXME: manual] note. iconic, honestly.

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NAME 🎀

glDrawArraysInstanced — draw multiple instances of a range of elements

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C SPECIFICATION 🧚

void glDrawArraysInstanced(GLenum mode, GLint first, GLsizei count,
                           GLsizei primcount);

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PARAMETERS 🌸

• mode — tells GL what kind of primitives to render. the accepted symbolic constants are GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, GL_TRIANGLES GL_LINES_ADJACENCY, GL_LINE_STRIP_ADJACENCY, GL_TRIANGLES_ADJACENCY, GL_TRIANGLE_STRIP_ADJACENCY and GL_PATCHES.
• first — the starting index in the enabled arrays.
• count — the number of indices to be rendered.
• primcount — the number of instances of the specified range of indices to be rendered.

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DESCRIPTION 🦋

glDrawArraysInstanced behaves identically to glDrawArrays() except that primcount instances of the range of elements are executed, and the value of the internal counter instanceID advances for each iteration. instanceID is an internal 32-bit integer counter that may be read by a vertex shader as gl_InstanceID.

it literally has the same effect as this, no cap:

if ( mode or count is invalid )
    generate appropriate error
else {
    for (int i = 0; i < primcount ; i++) {
        instanceID = i;
        glDrawArrays(mode, first, count);
    }
    instanceID = 0;
}

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ERRORS 🚨

• GL_INVALID_ENUM is generated if mode is not one of the accepted values.
• 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_VALUE is generated if count or primcount are negative.
• GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to an enabled array and the buffer object's data store is currently mapped.

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VERSION SUPPORT 👑

table tea: the row label is Function / Feature Name, the row itself is glDrawArraysInstanced, and the column header is OpenGL Version. here's the vibe check by version, fr fr:

• 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: ✔

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SEE ALSO 🔎

glDrawArrays(), glDrawElementsInstanced()

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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/.

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COPYRIGHT 📜 (yes, again, because the page says so)

Copyright © 2010-2014 Khronos Group

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okay bye bestie 💖 this one is sourced as [FIXME: source], dated 08/09/2021, and it signs off as the GLDRAWARRAYSINSTANCE(3G) page. mwah 🫶✨