diff options
Diffstat (limited to 'quaternion.c')
| -rw-r--r-- | quaternion.c | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/quaternion.c b/quaternion.c index 686c04e..ca44747 100644 --- a/quaternion.c +++ b/quaternion.c @@ -78,6 +78,24 @@ normq(Quaternion q) return sdivq(q, qlen(q)); } +/* + * based on the implementation from: + * + * Jonathan Blow, “Understanding Slerp, Then Not Using it”, + * The Inner Product, April 2004. + */ +Quaternion +slerp(Quaternion q, Quaternion r, double t) +{ + Quaternion v; + double θ, q·r; + + q·r = fclamp(dotq(q, r), -1, 1); /* stay within the domain of acos(2) */ + θ = acos(q·r)*t; + v = normq(subq(r, smulq(q, q·r))); /* v = r - (q·r)q / |v| */ + return addq(smulq(q, cos(θ)), smulq(v, sin(θ))); /* q cos(θ) + v sin(θ) */ +} + Point3 qrotate(Point3 p, Point3 axis, double θ) { |