GLDRAWTRANSFORMFEEDB(3G)

💅 NAME 💅

okay so bestie, glDrawTransformFeedbackInstanced — manual section 3G — is literally the glow-up that renders multiple instances of primitives using a count derived from a transform feedback object. no cap. ✨

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🎀 C SPECIFICATION 🎀

void glDrawTransformFeedbackInstanced(GLenum mode, GLuint id,
                                      GLsizei primcount);

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🌸 PARAMETERS 🌸

• mode — tells the GPU what kind of primitives to render, bestie. these symbolic constants are all accepted: 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.
• id — the name of a transform feedback object, like, the one you're pulling a primitive count out of. 🫶
• primcount — how many instances of the geometry you wanna render. that's it. that's the number.

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🦋 DESCRIPTION 🦋

so glDrawTransformFeedbackInstanced draws multiple copies of a range of primitives — type specified by mode — using a count it retrieved from the transform feedback stream specified by stream of the transform feedback object specified by id. iykyk 💫

calling glDrawTransformFeedbackInstanced is equivalent to calling glDrawArraysInstanced() with mode and primcount as specified, first set to zero, and count set to the number of vertices captured on vertex stream zero the last time transform feedback was active on the transform feedback object named by id. literally the same thing, she's just a shortcut. 👑

and calling glDrawTransformFeedbackInstanced is equivalent to calling glDrawTransformFeedbackStreamInstanced() with stream set to zero. no thoughts, same result. 🙈

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💀 ERRORS 💀

like, here's where things go off the rails — vibe check failed, bestie:

• GL_INVALID_ENUM is generated if mode is not an accepted value. 😭
• GL_INVALID_VALUE is generated if id is not the name of a transform feedback object.
• GL_INVALID_VALUE is generated if stream is greater than or equal to the value of GL_MAX_VERTEX_STREAMS.
• 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.
• 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.
• GL_INVALID_OPERATION is generated if glEndTransformFeedback has never been called while the transform feedback object named by id was bound. like girl. you have to end it. 💀

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🌈 VERSION SUPPORT 🌈

so the function name here is glDrawTransformFeedbackInstanced, and the OpenGL version tea is:

• OpenGL 2.0 — - nope
• OpenGL 2.1 — - nope
• OpenGL 3.0 — - nope
• OpenGL 3.1 — - nope
• OpenGL 3.2 — - nope
• OpenGL 3.3 — - nope
• OpenGL 4.0 — - nope
• OpenGL 4.1 — - nope
• OpenGL 4.2 — ✔ yes bestie
• OpenGL 4.3 — ✔ yes
• OpenGL 4.4 — ✔ yes
• OpenGL 4.5 — ✔ yes ✨

she didn't exist until 4.2 and honestly? she ate. 👑

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🧚 SEE ALSO 🧚

go read up on these icons, fr fr:

glDrawArrays(), glDrawArraysInstanced(), glDrawElements(), glDrawRangeElements(), glDrawTransformFeedback(), glDrawTransformFeedbackStreamInstanced().

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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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k that's the whole page, bestie 💖

mwah 💋 — this was [FIXME: source], dated 08/09/2021, and we're out. GLDRAWTRANSFORMFEEDB(3G) forever, periodt. 🌟