al_check_inverse(3alleg5)

✨ al_check_inverse ✨

okay bestie, welcome to the Allegro 5 API 💖 this one's a little function with a big job: it checks whether your transformation can actually be undone. no cap.

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🌸 SYNOPSIS 🌸

#include <allegro5/allegro.h>

int al_check_inverse(const ALLEGRO_TRANSFORM *trans, float tol)

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🦋 DESCRIPTION 🦋

so basically, al_check_inverse checks if the transformation has an inverse, using the tolerance you hand it. the tolerance should be a small value between 0 and 1, and honestly 1e-7 is enough for most applications. periodt.

here's the tea on how tolerance works in this function: it specifies how close the determinant can be to 0. (and reminder: if the determinant is 0, the transformation has no inverse.) so the smaller the tolerance you specify, the "worse" transformations will pass this test. using a tolerance of 1e-7 will catch errors greater than 1/1000's of a pixel, but let smaller errors pass. what does that mean in practice? it means if you transformed a point by a transformation and then transformed it again by the inverse transformation that passed this check, the resultant point should be less than 1/1000's of a pixel away from the original point. literally that precise. 💅

ngl, this check is superfluous most of the time if you never touched the transformation matrix values yourself. the only thing that would cause the transformation to not have an inverse is if you applied a 0 (or very small) scale to the transformation, or you have a really large translation. as long as the scale is comfortably above 0, the transformation will be invertible. slay.

Parameters: 🎀

• trans — Transformation to check
• tol — Tolerance

Returns: 1 if the transformation is invertible, 0 otherwise

⚠️ Note: Allegro's transformation inversion functions work correctly only with 2D transformations. so don't come for them with 3D, bestie 😭

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🌈 SEE ALSO 🌈

• al_invert_transform(3alleg5)

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and that's the whole vibe check, bestie 🫶 this was the Allegro reference manual, al_check_inverse(3alleg5) — go forth and check your inverses, you iconic main character 👑💜