AL_ORTHOGRAPHIC_TRANSFORM(3)

okay bestie, welcome to the al_orthographic_transform(3) page from the Library Functions Manual — it's giving Allegro 5 API realness, and we're gonna get you fluent in this transform. 💅

🌸 NAME 🌸

al_orthographic_transform — Allegro 5 API. That's the whole name-and-one-liner situation. 🎀

✨ SYNOPSIS ✨

Include this header, then call it like this:

              #include <allegro5/allegro.h>

              void al_orthographic_transform(ALLEGRO_TRANSFORM *trans,
                 float left, float top, float n,
                 float right, float bottom, float f)

💅 DESCRIPTION 💅

Okay so this function combines the given transformation with an orthographic transformation that maps the screen rectangle to the left/top and right/bottom coordinates you give it. Slay. 🦋

near/far is the z range, and coordinates outside that range will get clipped. Normally -1/1 is fine because all 2D graphics will have a z coordinate of 0. But if you, for example, do al_draw_rectangle(0, 0, 100, 100) and rotate around the x axis (“towards the screen”), make sure your z range allows values from -100 to 100 or the rotated rectangle will get clipped. No cap, that clipping is not the vibe. 😭

Also, if you're using a depth buffer, the z range decides the depth resolution. For example, if you have a 16 bit depth buffer there are only 65536 discrete depth values. So if your near/far is set to -1000000/1000000, most of the z positions would not result in separate depth values, which could lead to artifacts. This is the cautionary tale, bestie. 💀

The result of applying this transformation to coordinates will be to normalize visible coordinates into the cube from -1/-1/-1 to 1/1/1. Such a transformation is mostly useful for passing it to al_use_projection_transform(3) — see that function for an example use. 👑

🎀 SINCE 🎀

5.1.3 — periodt, that's when she landed. 💖

🦋 SEE ALSO 🦋

• al_use_projection_transform(3) — the function to pass this transform to; it has an example use. 🌈
• al_perspective_transform(3) — the other transform function on the see-also list. ✨

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💖 from the Allegro reference manual — Allegro 5 API, page al_orthographic_transform(3), SINCE 5.1.3 — no date in the footer, just vibes. Byeeee bestie 🫶