rtcGetGeo...sHalfEdge(3)

💅 rtcGetGeometryPreviousHalfEdge — bestie edition

okay so this one lives in the Embree Ray Tracing Kernels 4 manual, and it's genuinely so simple it's giving main character energy for like, three lines of code. let's get into it 🫶

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✨ NAME ✨

rtcGetGeometryPreviousHalfEdge — returns the previous half edge 🎀

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🌸 SYNOPSIS 🌸

#include <embree4/rtcore.h>

unsigned int rtcGetGeometryPreviousHalfEdge(
  RTCGeometry geometry,
  unsigned int edgeID
);

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💖 DESCRIPTION 💖

so the rtcGetGeometryPreviousHalfEdge function does exactly what it says on the tin: it returns the ID of the previous half edge of the half edge you hand it in the edgeID argument. literally that's it. no cap.

like, for instance, in the following example the previous half edge of e6 is e5. bestie said "walk backwards" and the kernel said "say less" 💅

🚨 okay important: this function can only be used for subdivision geometries. don't come at it with anything else, it's not gonna work out.

and here's the cute part — because all topologies of a subdivision geometry share the same face buffer, the function does not depend on the topology ID. so you don't gotta pass one in, she doesn't need it, she's self-sufficient like that. 👑

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😭 EXIT STATUS 😭

if something goes wrong (on failure), an error code gets set that you can go query with rtcGetDeviceError. so like, if it's acting up, that's where the receipts are. check it. fr fr.

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🦋 SEE ALSO 🦋

• [rtcGetGeometryFirstHalfEdge]
• [rtcGetGeometryFace]
• [rtcGetGeometryOppositeHalfEdge]
• [rtcGetGeometryNextHalfEdge]
• [rtcGetGeometryPreviousHalfEdge]

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okay that's the whole page, you're so welcome, go traverse some half edges the other direction for once 💜

signing off from the rtcGetGeo...sHalfEdge(3) page of the Embree Ray Tracing Kernels 4 manual — mwah, slay, periodt ✨👑🎀