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Fix integer truncation in quaternion setup

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Commit 47a6f744d split out redundant code, but accidentally stored
temporaries in a `signed short` instead of a `fix` as they should have
been.  This truncated some values, causing odd results whenever
quaternions were used.  Fix the problem by storing the intermediate
results in a `fix`.

Fixes: 47a6f744d8 ("Factor out vms_quaternion_from_matrix division")
Reported-by: Ninjared <https://forum.dxx-rebirth.com/showthread.php?tid=1113>
This commit is contained in:
Kp 2019-04-13 18:00:07 +00:00
parent 063bf29225
commit e61100a858
1 changed files with 21 additions and 21 deletions
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42
common/maths/vecmat.cpp
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@ -624,36 +624,36 @@ void vms_quaternion_from_matrix(vms_quaternion &rq, const vms_matrix &m)
const auto fy = m.fvec.y;
const auto fz = m.fvec.z;
const fix tr = rx + uy + fz;
vms_quaternion q;
fix qw, qx, qy, qz;
if (tr > 0) {
fix s = fixmul(fix_sqrt(tr + fl2f(1.0)), fl2f(2.0));
q.w = fixmul(fl2f(0.25), s);
q.x = fixdiv(fy - uz, s);
q.y = fixdiv(rz - fx, s);
q.z = fixdiv(ux - ry, s);
qw = fixmul(fl2f(0.25), s);
qx = fixdiv(fy - uz, s);
qy = fixdiv(rz - fx, s);
qz = fixdiv(ux - ry, s);
} else if ((rx > uy) & (rx > fz)) {
fix s = fixmul(fix_sqrt(fl2f(1.0) + rx - uy - fz), fl2f(2.0));
q.w = fixdiv(fy - uz, s);
q.x = fixmul(fl2f(0.25), s);
q.y = fixdiv(ry + ux, s);
q.z = fixdiv(rz + fx, s);
qw = fixdiv(fy - uz, s);
qx = fixmul(fl2f(0.25), s);
qy = fixdiv(ry + ux, s);
qz = fixdiv(rz + fx, s);
} else if (uy > fz) {
fix s = fixmul(fix_sqrt(fl2f(1.0) + uy - rx - fz), fl2f(2.0));
q.w = fixdiv(rz - fx, s);
q.x = fixdiv(ry + ux, s);
q.y = fixmul(fl2f(0.25), s);
q.z = fixdiv(uz + fy, s);
qw = fixdiv(rz - fx, s);
qx = fixdiv(ry + ux, s);
qy = fixmul(fl2f(0.25), s);
qz = fixdiv(uz + fy, s);
} else {
fix s = fixmul(fix_sqrt(fl2f(1.0) + fz - rx - uy), fl2f(2.0));
q.w = fixdiv(ux - ry, s);
q.x = fixdiv(rz + fx, s);
q.y = fixdiv(uz + fy, s);
q.z = fixmul(fl2f(0.25), s);
qw = fixdiv(ux - ry, s);
qx = fixdiv(rz + fx, s);
qy = fixdiv(uz + fy, s);
qz = fixmul(fl2f(0.25), s);
}
rq.w = q.w / 2;
rq.x = q.x / 2;
rq.y = q.y / 2;
rq.z = q.z / 2;
rq.w = qw / 2;
rq.x = qx / 2;
rq.y = qy / 2;
rq.z = qz / 2;
}
// convert vms_quaternion to vms_matrix