GLUBEGINSURFACE(3G)

💖 GLUBEGINSURFACE(3G) — okay bestie, let's talk NURBS surfaces ✨

gluBeginSurface, gluEndSurface — delimit a NURBS surface definition 🦋

Like, this whole page lives in section 3G of the manual, iykyk. It's giving OpenGL utility library energy and honestly? Iconic. 🎀

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✨ NAME ✨

gluBeginSurface, gluEndSurface — delimit a NURBS surface definition 💫

No cap, that's the whole vibe: you're wrapping a surface definition in a little begin/end sandwich. 🥪

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🌸 C SPECIFICATION 🌸

Sit down, grab a strawberry 🍓, here's exactly what you call:

void gluBeginSurface( GLUnurbs* nurb )

void gluEndSurface( GLUnurbs* nurb )

Not me being obsessed with how clean that is. 💅

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🎀 PARAMETERS 🎀

• nurb — specifies the NURBS object, and bestie it has to be one that was created with gluNewNurbsRenderer. Like, that's the whole origin story. 🌱

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💜 DESCRIPTION 💜

Okay so. gluBeginSurface is your lil "we're doing this now" announcement — it marks the beginning of a NURBS surface definition. 🫶

Once you've called gluBeginSurface, you make one or more calls to gluNurbsSurface to define the attributes of the surface. Multiple calls, go off. 👑

But here's the rule that matters, and I need you to lock in fr fr: exactly one of those calls to gluNurbsSurface must have a surface type of GL_MAP2_VERTEX_3 or GL_MAP2_VERTEX_4. Exactly one. Not zero, not two. EXACTLY ONE. 😭

Then to mark the end of the NURBS surface definition, you call gluEndSurface. Wrap it up, we're done here, slay. ✨

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Trimming of NURBS surfaces is supported with gluBeginTrim, gluPwlCurve, gluNurbsCurve, and gluEndTrim. 💇‍♀️ Yes bestie, trimming — like a haircut for your surface. If you want the details, go read the gluBeginTrim reference page, it's got the whole story.

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GL evaluators are used to render the NURBS surface as a set of polygons. 📐

And the evaluator state? Preserved during rendering, thank u next — that's what glPushAttrib(GL_EVAL_BIT) and glPopAttrib() are doing for you. 🧚

Heads up: if you want to know exactly what state those calls preserve, the glPushAttrib reference page has the receipts. Go check it, I'm not guessing for you. 💀

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🌈 EXAMPLE 🌈

Okay here's the moment you've been waiting for. The following commands render a textured NURBS surface with normals — and plot twist, the texture coordinates and the normals are also described as NURBS surfaces. Recursion? No, just main character energy. 👑

gluBeginSurface(nobj);
   gluNurbsSurface(nobj, ..., GL_MAP2_TEXTURE_COORD_2);
   gluNurbsSurface(nobj, ..., GL_MAP2_NORMAL);
   gluNurbsSurface(nobj, ..., GL_MAP2_VERTEX_4); gluEndSurface(nobj);

See how there's exactly one GL_MAP2_VERTEX_4 in there? Yeah. That's the rule. We love a queen who follows the rules. 💅 And yes, gluEndSurface(nobj) is just chilling at the end of that last line, no drama. 🌸

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🔥 SEE ALSO 🔥

Go read these next, they're all part of the friend group:

• gluBeginCurve(3G)
• gluBeginTrim(3G)
• gluNewNurbsRenderer(3G)
• gluNurbsCurve(3G)
• gluNurbsSurface(3G)
• gluPwlCurve(3G)

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bestie there's more where that came from, don't go anywhere 💖

✨ EXAMPLE ✨

okay so bestie, picture this: you wanna render a textured NURBS surface with normals, and the texture coords AND the normals are themselves described as NURBS surfaces 🦋. Here's exactly how the commands go:

gluBeginSurface(nobj);
   gluNurbsSurface(nobj, ..., GL_MAP2_TEXTURE_COORD_2);
   gluNurbsSurface(nobj, ..., GL_MAP2_NORMAL);
   gluNurbsSurface(nobj, ..., GL_MAP2_VERTEX_4); gluEndSurface(nobj);

notice how it's the whole little sandwich: open with gluBeginSurface(nobj), stack up your gluNurbsSurface calls for texture coords and normals, then the GL_MAP2_VERTEX_4 one rides in and gluEndSurface(nobj) shuts it all down 💅. the ... is standing in for the actual args, so don't come for me, that's literally what the page shows 🙈.

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🌈 SEE ALSO 🌈

go read these next, they're all part of the same friend group fr fr:

• gluBeginCurve(3G)
• gluBeginTrim(3G)
• gluNewNurbsRenderer(3G)
• gluNurbsCurve(3G)
• gluNurbsSurface(3G)
• gluPwlCurve(3G)

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okay and that's a wrap on the whole page, bestie 🎀. this one lives in the manual under GLUBEGINSURFACE(3G), and that cute lil tag you see at the very bottom of every manpage is just the page's own name and section waving back at you 👑. go forth, delimit those surfaces, and slay ✨💖