vpClassifyScanline(3)

💖 vpClassifyScanline — from the VolPack library manual, section 3 💖

okay bestie, gather round, because we're about to talk about vpClassifyScanline(3) from the VolPack library — yes, the Library Functions Manual one, the legend herself. she's the girl who builds your preclassified volume one scanline at a time, and honestly? she ate. 🍓

✨ NAME ✨

vpClassifyScanline — incrementally create a preclassified volume from scanlines of scalar data. like, little by little, scanline by scanline, no cap. 💅

🌸 SYNOPSIS 🌸

#include <volpack.h>

vpResult
vpClassifyScanline(vpc, voxels)
    vpContext *vpc;
    void *voxels;

🎀 ARGUMENTS 🎀

• vpc — the VolPack context you got from vpCreateContext. your main character struct, basically. 👑
• voxels — a 1D array of voxel data. just a lil lineup of voxels, living their truth.

🦋 DESCRIPTION 🦋

so the way that vpClassifyScanline works is: you use her to incrementally compute a preclassified volume. she classifies one scanline of voxels at a time and drops the result straight into the current preclassified volume. one at a time, bestie. she's not doing all of it at once, that's not her vibe.

the voxels argument is a 1D array holding voxels in the format you already specified earlier with vpSetVoxelSize and vpSetVoxelField. and listen — you must call vpVolumeSize to declare the size of the volume before the very first call to vpClassifyScanline. non-negotiable. also, the length of that 1D voxel array has to be exactly equal to the length of the X dimension of the volume. not more, not less, exactly. ✨

and guess what, you can initialize that 1D voxel array with vpScanlineNormals or with your own user-defined function — your call, your era. 💖

the voxels in the array get classified using the current opacity transfer function (go peek at vpSetClassifierTable(3)) and then they're appended to the preclassified volume (hi vpClassifyVolume(3), ily). 🌈

now here's the part you can't skip: scanlines must be processed in Z-major order. so all the scanlines in the Z=0 slice get processed starting from Y=0 onward, then the Z=1 slice gets processed, and so on forever until you're done. no jumping around, that's giving chaos energy and the volume does not want that. 🙈

once the last scanline in the volume has been processed, the preclassified data structure is ready to be used for rendering. slay! but — and this is important — rendering is not possible until all scanlines have been processed. not a single one. don't even try it. 💀

⚠️ and when the first scanline of a volume gets passed to vpClassifyScanline, any existing preclassified volume data is destroyed. gone. deleted. she does not do leftovers. 😭

👑 ERRORS 👑

the normal return value is VP_OK. iconic. but the following error return values are possible, and yes, you will meet them:

• VPERROR_BAD_VOXEL — the voxel size or the voxel fields have not been specified, or they've been incorrectly specified. like girl, we needed those. 😭
• VPERROR_BAD_CLASSIFIER — the opacity transfer function tables have invalid sizes, or they're associated with invalid voxel fields, or they've been incorrectly specified. messy. 💅

💜 SEE ALSO 💜

VolPack(3), vpCreateContext(3), vpSetClassifierTable(3), vpClassifyVolume(3), vpClassifyScalars(3) — the whole friend group, go read them, iykyk. 🫶

okay that's the whole page bestie, and as a lil sign-off: this one comes to you from VolPack — that's the source/version vibe — under the vpClassifyScanline(3) name, exactly like the header says at the top. periodt. 🎀✨