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add some comments about the coordinate systems used in AngleVectors

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Bill Currie 2003-03-10 20:44:50 +00:00
parent a565f2f9ea
commit 72d1343735
1 changed files with 35 additions and 3 deletions
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38
libs/util/mathlib.c
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@ -307,6 +307,36 @@ BoxOnPlaneSide (const vec3_t emins, const vec3_t emaxs, mplane_t *p)
}
#endif
/*
angles is a left(?) handed system: 'pitch yaw roll' with x (pitch) axis to
the right, y (yaw) axis up and z (roll) axis forward.
the math in AngleVectors has the entity frame as left handed with x
(forward) axis forward, y (right) axis to the right and z (up) up. However,
the world is a right (?) handed system with x to the right, y forward and
z up.
pitch =
cp 0 -sp
0 1 0
sp 0 cp
yaw =
cy sy 0
-sy cy 0
0 0 1
roll =
1 0 0
0 cr sr
0 -sr cr
final = roll * (pitch * yaw)
final =
[forward]
[-right] -ve due to left handed to right handed conversion
[up]
*/
void
AngleVectors (const vec3_t angles, vec3_t forward, vec3_t right, vec3_t up)
{
@ -325,9 +355,11 @@ AngleVectors (const vec3_t angles, vec3_t forward, vec3_t right, vec3_t up)
forward[0] = cp * cy;
forward[1] = cp * sy;
forward[2] = -sp;
right[0] = (-1 * sr * sp * cy + -1 * cr * -sy);
right[1] = (-1 * sr * sp * sy + -1 * cr * cy);
right[2] = -1 * sr * cp;
// need to flip right because it's a left handed system in a right handed
// world
right[0] = -1 * (sr * sp * cy + cr * -sy);
right[1] = -1 * (sr * sp * sy + cr * cy);
right[2] = -1 * (sr * cp);
up[0] = (cr * sp * cy + -sr * -sy);
up[1] = (cr * sp * sy + -sr * cy);
up[2] = cr * cp;