Modern Math Rotate

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Rotate

Rotates a vector by a normalised quaternion.

Syntax

Rotate( byref q as Quat, byref v as Vec3 ) as Vec3

Notes

• Assumes q is normalised -- an unnormalised quaternion scales the vector as well as turning it.
• Cheaper than building a matrix when only a few vectors are being rotated; ToMatrix wins when there are many.
• The identity quaternion leaves the vector alone, which is the cheapest sanity check there is.

Examples

#import "std/numeric"
using numeric

dim as Quat q = type<Quat>( 0, 0, 0, 1 )      '' identity
dim as Vec3 v = type<Vec3>( 1, 2, 3 )

dim as Vec3 r = Rotate( q, v )
print r.x & " " & r.y & " " & r.z             '' 1 2 3 -- unchanged

'' A rotation preserves length, which is the other cheap check
print abs( Length( r ) - Length( v ) ) < 0.0001        '' -1 (true)

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Library: Math Library
Category: Math Library
Documented under: Members