Title:  Fast Quad Rotation
Brief:  A better way to rotate quads around their centers.
Date:   1722126213
Tags:   Programming, Optimization, C
CSS:    /style.css

A similar in essence trick to [by pi rotation](/articles/vector-pi-rotation.html), but with delta calculated
for some corner which is reused later with negation and coordinate swap.

Scaling by `M_SQRT1_2` is there to retain the quad size (Pythagorean stuffs).

### Code ###
```c
const t_fvec2 c = frect_center(sprite.rect);
const t_fvec2 d = {
    .x = (cosf(sprite.rotation + (float)M_PI_4) * sprite.rect.w) * (float)M_SQRT1_2,
    .y = (sinf(sprite.rotation + (float)M_PI_4) * sprite.rect.h) * (float)M_SQRT1_2,
};

/* upper-left */
const t_fvec2 v0 = { c.x - d.x, c.y - d.y };

/* bottom-left */
const t_fvec2 v1 = { c.x - d.y, c.y + d.x };

/* bottom-right */
const t_fvec2 v2 = { c.x + d.x, c.y + d.y };

/* upper-right */
const t_fvec2 v3 = { c.x + d.y, c.y - d.x };

```