From da0b16d79c05a83d14195eaf509352effbe5a215 Mon Sep 17 00:00:00 2001 From: Tavian Barnes Date: Fri, 27 Nov 2009 01:43:36 -0500 Subject: Fake camera semantics until I figure out the real ones. --- libdimension/geometry.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'libdimension/geometry.c') diff --git a/libdimension/geometry.c b/libdimension/geometry.c index cbcc2c1..4aa46ec 100644 --- a/libdimension/geometry.c +++ b/libdimension/geometry.c @@ -80,6 +80,23 @@ dmnsn_rotation_matrix(dmnsn_vector theta) ); } +/* Find the angle between two vectors with respect to an axis */ +double +dmnsn_vector_axis_angle(dmnsn_vector v1, dmnsn_vector v2, dmnsn_vector axis) +{ + dmnsn_vector d = dmnsn_vector_sub(v1, v2); + dmnsn_vector proj = dmnsn_vector_add(dmnsn_vector_proj(d, axis), v2); + + double c = dmnsn_vector_dot(dmnsn_vector_normalize(v1), + dmnsn_vector_normalize(proj)); + double angle = acos(c); + + if (dmnsn_vector_dot(dmnsn_vector_cross(v1, proj), axis) > 0) + return angle; + else + return -angle; +} + /* Matrix inversion helper functions */ typedef struct { double n[2][2]; } dmnsn_matrix2; -- cgit v1.2.3