math.vec: add rotate_around_* (cw/ccw) functions to vec.Vec2[T] (#23807)

Author: larpon

vlib/math/vec/vec2.v

@@ -258,6 +258,23 @@ pub fn (v Vec2[T]) project(u Vec2[T]) Vec2[T] {
 	return u.mul_scalar(percent)
 }
 
+// rotate_around_cw returns the vector `v` rotated *clockwise* `radians` around an origin vector `o` in Cartesian space.
+pub fn (v Vec2[T]) rotate_around_cw(o Vec2[T], radians f64) Vec2[T] {
+	return v.rotate_around_ccw(o, -radians)
+}
+
+// rotate_around_ccw returns the vector `v` rotated *counter-clockwise* `radians` around an origin vector `o` in Cartesian space.
+pub fn (v Vec2[T]) rotate_around_ccw(o Vec2[T], radians f64) Vec2[T] {
+	s := math.sin(radians)
+	c := math.cos(radians)
+	dx := v.x - o.x
+	dy := v.y - o.y
+	return Vec2[T]{
+		x: T(c * dx - s * dy + o.x)
+		y: T(s * dx + c * dy + o.y)
+	}
+}
+
 // eq returns a bool indicating if the two vectors are equal.
 @[inline]
 pub fn (v Vec2[T]) eq(u Vec2[T]) bool {

vlib/math/vec/vec2_test.v

@@ -1,4 +1,4 @@
-import math { close, veryclose }
+import math { close, radians, veryclose }
 import math.vec
 
 fn test_vec2_int() {
@@ -160,3 +160,71 @@ fn test_vec2_angle_towards() {
 		}
 	}
 }
+
+fn test_vec2_rotate_around_cw() {
+	origin := vec.vec2(0.0, 0.0)
+	mut v := vec.vec2(0.0, 1.0)
+	v = v.rotate_around_cw(origin, radians(90))
+	assert close(v.x, 1.0)
+	assert close(v.y, 0.0)
+	v = v.rotate_around_cw(origin, radians(90))
+	assert close(v.x, 0.0)
+	assert close(v.y, -1.0)
+	v = v.rotate_around_cw(origin, radians(90))
+	assert close(v.x, -1.0)
+	assert close(v.y, 0.0)
+	v = v.rotate_around_cw(origin, radians(90))
+	assert close(v.x, 0.0)
+	assert close(v.y, 1.0)
+}
+
+fn test_vec2_rotate_around_ccw() {
+	origin := vec.vec2(0.0, 0.0)
+	mut v := vec.vec2(0.0, 1.0)
+	v = v.rotate_around_ccw(origin, radians(90))
+	assert close(v.x, -1.0)
+	assert close(v.y, 0.0)
+	v = v.rotate_around_ccw(origin, radians(90))
+	assert close(v.x, 0.0)
+	assert close(v.y, -1.0)
+	v = v.rotate_around_ccw(origin, radians(90))
+	assert close(v.x, 1.0)
+	assert close(v.y, 0.0)
+	v = v.rotate_around_ccw(origin, radians(90))
+	assert close(v.x, 0.0)
+	assert close(v.y, 1.0)
+}
+
+fn test_vec2_rotate_around_cw_2() {
+	origin := vec.vec2(1.0, 1.0)
+	mut v := vec.vec2(1.0, 2.0)
+	v = v.rotate_around_cw(origin, radians(90))
+	assert close(v.x, 2.0)
+	assert close(v.y, 1.0)
+	v = v.rotate_around_cw(origin, radians(90))
+	assert close(v.x, 1.0)
+	assert close(v.y, 0.0)
+	v = v.rotate_around_cw(origin, radians(90))
+	assert close(v.x, 0.0)
+	assert close(v.y, 1.0)
+	v = v.rotate_around_cw(origin, radians(90))
+	assert close(v.x, 1.0)
+	assert close(v.y, 2.0)
+}
+
+fn test_vec2_rotate_around_ccw_2() {
+	origin := vec.vec2(-1.0, 1.0)
+	mut v := vec.vec2(-1.0, -1.0)
+	v = v.rotate_around_ccw(origin, radians(90))
+	assert close(v.x, 1.0)
+	assert close(v.y, 1.0)
+	v = v.rotate_around_ccw(origin, radians(90))
+	assert close(v.x, -1.0)
+	assert close(v.y, 3.0)
+	v = v.rotate_around_ccw(origin, radians(90))
+	assert close(v.x, -3.0)
+	assert close(v.y, 1.0)
+	v = v.rotate_around_ccw(origin, radians(90))
+	assert close(v.x, -1.0)
+	assert close(v.y, -1.0)
+}