rtcInitPo...ryContext(3)

💖 NAME 💖

rtcInitPointQueryContext — bestie, this is the one that sets up your context info (like, the stack of (multilevel-)instance transformations) for point queries ✨

🎀 SYNOPSIS 🎀

#include <embree4/rtcore.h>

struct RTC_ALIGN(16) RTCPointQueryContext
{
  // accumulated 4x4 column major matrices from world to instance space.
  float world2inst[RTC_MAX_INSTANCE_LEVEL_COUNT][16];

  // accumulated 4x4 column major matrices from instance to world space.
  float inst2world[RTC_MAX_INSTANCE_LEVEL_COUNT][16];

  // instance ids.
  unsigned int instID[RTC_MAX_INSTANCE_LEVEL_COUNT];

  // number of instances currently on the stack.
  unsigned int instStackSize;
};

void rtcInitPointQueryContext(
  struct RTCPointQueryContext* context
);

🌸 DESCRIPTION 🌸

Okay so picture a stack — and it's literally the RTCPointQueryContext type — that holds onto the IDs and the instance transformations while a BVH traversal is happening for a point query. The way that these transformations are assumed to be affine transformations (that's a 3×3 matrix plus a translation, iykyk) means the last column just gets ignored, no cap. (peep [RTC_GEOMETRY_TYPE_INSTANCE] if you want the deets 👀)

The rtcInitPointContext function initializes the context to its default values, and bestie, you should be calling it for initialization. That's the vibe check. 💅

So the context gets passed as an argument to the point query callback function (see [rtcSetGeometryPointQueryFunction]) and you're gonna use it to pass instance information down the instancing chain for user defined instancing — the tutorial [ClosestPoint] has a reference implementation of point queries with user defined instancing if you want to see it done right 🫶

And lowkey important: the context is a necessary argument to [rtcPointQuery]. Embree internally grabs the topmost instance transformation off the stack to transform the point query into instance space. Main character transformation behavior fr fr ✨

💀 EXIT STATUS 💀

No error code is set by this function. Zero drama, zero errors, iconic behavior. 👑

🌈 SEE ALSO 🌈

• [rtcPointQuery]
• [rtcSetGeometryPointQueryFunction]

okay that's the whole page bestie, go forth and init your context 💜 This was rtcInitPo...ryContext(3) from Embree Ray Tracing Kernels 4 — mwah, stan, bye 🎀🦋