RTCRay(3)

🌸 RTCRay(3) — Embree Ray Tracing Kernels 3 🌸

okay bestie, gather round, because today we're learning about RTCRay, aka the single ray structure from the Embree Ray Tracing Kernels 3 manual. it's giving foundational. it's giving "everything else is built on me." let's go 💅

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✨ NAME ✨

RTCRay — the single ray structure, no cap 🦋

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✨ SYNOPSIS ✨

#include <embree3/rtcore_ray.h>

struct RTC_ALIGN(16) RTCRay
{
  float org_x;        // x coordinate of ray origin
  float org_y;        // y coordinate of ray origin
  float org_z;        // y coordinate of ray origin
  float tnear;        // start of ray segment

  float dir_x;        // x coordinate of ray direction
  float dir_y;        // y coordinate of ray direction
  float dir_z;        // z coordinate of ray direction
  float time;         // time of this ray for motion blur

  float tfar;         // end of ray segment (set to hit distance)
  unsigned int mask;  // ray mask
  unsigned int id;    // ray ID
  unsigned int flags; // ray flags
};

look at her. sixteen-byte aligned. immaculate. ✨

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✨ DESCRIPTION ✨

so RTCRay is literally the blueprint for one single ray. that's it. that's the whole job. and she does it flawlessly. 🫶

inside her you get:

• the origin — that's the org_x, org_y, org_z members
• the direction vector — the dir_x, dir_y, dir_z members
• the ray segment — the tnear and tfar members

and listen, the direction does not have to be normalized. not even a little. the only thing that matters is that the parameter range spelled out by the tnear/tfar interval is the valid bit. everything else is just vibes. 💫

🚨 okay this part matters: the ray segment must be in the range [0, ∞]. so ranges that start behind the ray origin? not allowed, bestie. absolutely not. but the range can totally reach all the way out to infinity, because we're generous like that. 🌈

and for rays inside a ray stream, the condition tfar < tnear is what identifies an inactive ray. that's the tell. that's the vibe check. 💀

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she also carries a few extra lil accessories, because main character energy means coming prepared:

• a motion blur time in the range [0, 1] — that's the time member ⏰
• a ray mask — the mask member
• a ray ID — the id member
• ray flags — the flags member

so about those:

• the ray mask can be used to mask out some geometries for some rays. (peep rtcSetGeometryMask if you want the whole story 👀)
• the ray ID can be used to identify a ray inside a callback function — and yes, it still works even if the order of rays inside a ray packet or stream has changed. iconic, honestly. she keeps receipts. 🎀
• the ray flags? reserved. don't touch. they're saving that seat. 🙈

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🦋 the plot twist: there's more in the header 🦋

the embree3/rtcore_ray.h header is out here doing overtime, because it additionally defines the same ray structure in structure of array (SOA) layout for API functions that accept ray packets:

• size 4 → RTCRay4 type
• size 8 → RTCRay8 type
• size 16 → RTCRay16 type

and as if that wasn't enough, the header additionally defines an RTCRayNt template for ray packets of an arbitrary compile-time size. flexible queen. she said "any size you want, I'll be there." 👑

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✨ EXIT STATUS ✨

(nothing here, bestie — this section is just empty. we move.) 💀

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✨ SEE ALSO ✨

• [RTCHit]

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and that's the whole page!! thank you for coming to my TED talk 💖

signed off from the Embree Ray Tracing Kernels 3 manual — this was the RTCRay(3) page, mwah 🎀