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o3de/Code/Editor/Util/AffineParts.cpp

856 lines
23 KiB
C++

/*
* Copyright (c) Contributors to the Open 3D Engine Project.
* For complete copyright and license terms please see the LICENSE at the root of this distribution.
*
* SPDX-License-Identifier: Apache-2.0 OR MIT
*
*/
#include "EditorDefs.h"
/**** Decompose.h - Basic declarations ****/
typedef struct
{
float x, y, z, w;
} Quatern; /* Quaternernion */
enum QuaternPart
{
X, Y, Z, W
};
typedef Quatern HVect; /* Homogeneous 3D vector */
typedef float HMatrix[4][4]; /* Right-handed, for column vectors */
typedef struct
{
HVect t; /* Translation components */
Quatern q; /* Essential rotation */
Quatern u; /* Stretch rotation */
HVect k; /* Stretch factors */
float f; /* Sign of determinant */
} SAffineParts;
float polar_decomp(HMatrix M, HMatrix Q, HMatrix S);
HVect spect_decomp(HMatrix S, HMatrix U);
Quatern snuggle(Quatern q, HVect* k);
/******* Matrix Preliminaries *******/
/** Fill out 3x3 matrix to 4x4 **/
#define mat_pad(A) (A[W][X] = A[X][W] = A[W][Y] = A[Y][W] = A[W][Z] = A[Z][W] = 0, A[W][W] = 1)
/** Copy nxn matrix A to C using "gets" for assignment **/
#define mat_copy(C, gets, A, n) {int i, j; for (i = 0; i < n; i++) {for (j = 0; j < n; j++) { \
C[i][j] gets (A[i][j]); } \
} \
}
/** Copy transpose of nxn matrix A to C using "gets" for assignment **/
#define mat_tpose(AT, gets, A, n) {int i, j; for (i = 0; i < n; i++) {for (j = 0; j < n; j++) { \
AT[i][j] gets (A[j][i]); } \
} \
}
/** Assign nxn matrix C the element-wise combination of A and B using "op" **/
#define mat_binop(C, gets, A, op, B, n) {int i, j; for (i = 0; i < n; i++) {for (j = 0; j < n; j++) { \
C[i][j] gets (A[i][j]) op (B[i][j]); } \
} \
}
/** Multiply the upper left 3x3 parts of A and B to get AB **/
static void mat_mult(HMatrix A, HMatrix B, HMatrix AB)
{
int i, j;
for (i = 0; i < 3; i++)
{
for (j = 0; j < 3; j++)
{
AB[i][j] = A[i][0] * B[0][j] + A[i][1] * B[1][j] + A[i][2] * B[2][j];
}
}
}
/** Return dot product of length 3 vectors va and vb **/
static float vdot(float* va, float* vb)
{
return (va[0] * vb[0] + va[1] * vb[1] + va[2] * vb[2]);
}
/** Set v to cross product of length 3 vectors va and vb **/
static void vcross(float* va, float* vb, float* v)
{
v[0] = va[1] * vb[2] - va[2] * vb[1];
v[1] = va[2] * vb[0] - va[0] * vb[2];
v[2] = va[0] * vb[1] - va[1] * vb[0];
}
/** Set MadjT to transpose of inverse of M times determinant of M **/
static void adjoint_transpose(HMatrix M, HMatrix MadjT)
{
vcross(M[1], M[2], MadjT[0]);
vcross(M[2], M[0], MadjT[1]);
vcross(M[0], M[1], MadjT[2]);
}
/******* Quaternernion Preliminaries *******/
/* Construct a (possibly non-unit) Quaternernion from real components. */
static Quatern Qt_(float x, float y, float z, float w)
{
Quatern qq;
qq.x = x;
qq.y = y;
qq.z = z;
qq.w = w;
return (qq);
}
/* Return conjugate of Quaternernion. */
static Quatern Qt_Conj(Quatern q)
{
Quatern qq;
qq.x = -q.x;
qq.y = -q.y;
qq.z = -q.z;
qq.w = q.w;
return (qq);
}
/* Return Quaternernion product qL * qR. Note: order is important!
* To combine rotations, use the product Mul(qSecond, qFirst),
* which gives the effect of rotating by qFirst then qSecond. */
static Quatern Qt_Mul(Quatern qL, Quatern qR)
{
Quatern qq;
qq.w = qL.w * qR.w - qL.x * qR.x - qL.y * qR.y - qL.z * qR.z;
qq.x = qL.w * qR.x + qL.x * qR.w + qL.y * qR.z - qL.z * qR.y;
qq.y = qL.w * qR.y + qL.y * qR.w + qL.z * qR.x - qL.x * qR.z;
qq.z = qL.w * qR.z + qL.z * qR.w + qL.x * qR.y - qL.y * qR.x;
return (qq);
}
/* Return product of Quaternernion q by scalar w. */
static Quatern Qt_Scale(Quatern q, float w)
{
Quatern qq;
qq.w = q.w * w;
qq.x = q.x * w;
qq.y = q.y * w;
qq.z = q.z * w;
return (qq);
}
/* Construct a unit Quaternernion from rotation matrix. Assumes matrix is
* used to multiply column vector on the left: vnew = mat vold. Works
* correctly for right-handed coordinate system and right-handed rotations.
* Translation and perspective components ignored. */
static Quatern Qt_FromMatrix(HMatrix mat)
{
/* This algorithm avoids near-zero divides by looking for a large component
* - first w, then x, y, or z. When the trace is greater than zero,
* |w| is greater than 1/2, which is as small as a largest component can be.
* Otherwise, the largest diagonal entry corresponds to the largest of |x|,
* |y|, or |z|, one of which must be larger than |w|, and at least 1/2. */
Quatern qu = { 0.0f, 0.0f, 0.0f, 1.0f };
double tr, s;
tr = mat[X][X] + mat[Y][Y] + mat[Z][Z];
if (tr >= 0.0)
{
s = sqrt(tr + mat[W][W]);
qu.w = static_cast<float>(s * 0.5);
s = 0.5 / s;
qu.x = static_cast<float>((mat[Z][Y] - mat[Y][Z]) * s);
qu.y = static_cast<float>((mat[X][Z] - mat[Z][X]) * s);
qu.z = static_cast<float>((mat[Y][X] - mat[X][Y]) * s);
}
else
{
int h = X;
if (mat[Y][Y] > mat[X][X])
{
h = Y;
}
if (mat[Z][Z] > mat[h][h])
{
h = Z;
}
switch (h)
{
#define caseMacro(i, j, k, I, J, K) \
case I: \
s = sqrt((mat[I][I] - (mat[J][J] + mat[K][K])) + mat[W][W]); \
qu.i = static_cast<float>(s * 0.5); \
s = 0.5 / s; \
qu.j = static_cast<float>((mat[I][J] + mat[J][I]) * s); \
qu.k = static_cast<float>((mat[K][I] + mat[I][K]) * s); \
qu.w = static_cast<float>((mat[K][J] - mat[J][K]) * s); \
break
caseMacro(x, y, z, X, Y, Z);
caseMacro(y, z, x, Y, Z, X);
caseMacro(z, x, y, Z, X, Y);
}
}
if (mat[W][W] != 1.0)
{
qu = Qt_Scale(qu, 1.0f / sqrt(mat[W][W]));
}
return (qu);
}
/******* Decomp Auxiliaries *******/
static HMatrix mat_id = {
{1, 0, 0, 0}, {0, 1, 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1}
};
/** Compute either the 1 or infinity norm of M, depending on tpose **/
static float mat_norm(HMatrix M, int tpose)
{
int i;
float sum, max;
max = 0.0;
for (i = 0; i < 3; i++)
{
if (tpose)
{
sum = fabs(M[0][i]) + fabs(M[1][i]) + fabs(M[2][i]);
}
else
{
sum = fabs(M[i][0]) + fabs(M[i][1]) + fabs(M[i][2]);
}
if (max < sum)
{
max = sum;
}
}
return max;
}
static float norm_inf(HMatrix M) {return mat_norm(M, 0); }
static float norm_one(HMatrix M) {return mat_norm(M, 1); }
/** Return index of column of M containing maximum abs entry, or -1 if M=0 **/
static int find_max_col(HMatrix M)
{
float abs, max;
int i, j, col;
max = 0.0;
col = -1;
for (i = 0; i < 3; i++)
{
for (j = 0; j < 3; j++)
{
abs = M[i][j];
if (abs < 0.0)
{
abs = -abs;
}
if (abs > max)
{
max = abs;
col = j;
}
}
}
return col;
}
/** Setup u for Household reflection to zero all v components but first **/
static void make_reflector(float* v, float* u)
{
float s = sqrt(vdot(v, v));
u[0] = v[0];
u[1] = v[1];
u[2] = v[2] + ((v[2] < 0.0) ? -s : s);
s = static_cast<float>(sqrt(2.0f / vdot(u, u)));
u[0] = u[0] * s;
u[1] = u[1] * s;
u[2] = u[2] * s;
}
/** Apply Householder reflection represented by u to column vectors of M **/
static void reflect_cols(HMatrix M, float* u)
{
int i, j;
for (i = 0; i < 3; i++)
{
float s = u[0] * M[0][i] + u[1] * M[1][i] + u[2] * M[2][i];
for (j = 0; j < 3; j++)
{
M[j][i] -= u[j] * s;
}
}
}
/** Apply Householder reflection represented by u to row vectors of M **/
static void reflect_rows(HMatrix M, float* u)
{
int i, j;
for (i = 0; i < 3; i++)
{
float s = vdot(u, M[i]);
for (j = 0; j < 3; j++)
{
M[i][j] -= u[j] * s;
}
}
}
/** Find orthogonal factor Q of rank 1 (or less) M **/
static void do_rank1(HMatrix M, HMatrix Q)
{
float v1[3], v2[3], s;
int col;
mat_copy(Q, =, mat_id, 4);
/* If rank(M) is 1, we should find a non-zero column in M */
col = find_max_col(M);
if (col < 0)
{
return; /* Rank is 0 */
}
v1[0] = M[0][col];
v1[1] = M[1][col];
v1[2] = M[2][col];
make_reflector(v1, v1);
reflect_cols(M, v1);
v2[0] = M[2][0];
v2[1] = M[2][1];
v2[2] = M[2][2];
make_reflector(v2, v2);
reflect_rows(M, v2);
s = M[2][2];
if (s < 0.0)
{
Q[2][2] = -1.0;
}
reflect_cols(Q, v1);
reflect_rows(Q, v2);
}
/** Find orthogonal factor Q of rank 2 (or less) M using adjoint transpose **/
static void do_rank2(HMatrix M, HMatrix MadjT, HMatrix Q)
{
float v1[3], v2[3];
float w, x, y, z, c, s, d;
int col;
/* If rank(M) is 2, we should find a non-zero column in MadjT */
col = find_max_col(MadjT);
if (col < 0)
{
do_rank1(M, Q);
return;
} /* Rank<2 */
v1[0] = MadjT[0][col];
v1[1] = MadjT[1][col];
v1[2] = MadjT[2][col];
make_reflector(v1, v1);
reflect_cols(M, v1);
vcross(M[0], M[1], v2);
make_reflector(v2, v2);
reflect_rows(M, v2);
w = M[0][0];
x = M[0][1];
y = M[1][0];
z = M[1][1];
if (w * z > x * y)
{
c = z + w;
s = y - x;
d = sqrt(c * c + s * s);
c = c / d;
s = s / d;
Q[0][0] = Q[1][1] = c;
Q[0][1] = -(Q[1][0] = s);
}
else
{
c = z - w;
s = y + x;
d = sqrt(c * c + s * s);
c = c / d;
s = s / d;
Q[0][0] = -(Q[1][1] = c);
Q[0][1] = Q[1][0] = s;
}
Q[0][2] = Q[2][0] = Q[1][2] = Q[2][1] = 0.0;
Q[2][2] = 1.0;
reflect_cols(Q, v1);
reflect_rows(Q, v2);
}
/******* Polar Decomposition *******/
/* Polar Decomposition of 3x3 matrix in 4x4,
* M = QS. See Nicholas Higham and Robert S. Schreiber,
* Fast Polar Decomposition of An Arbitrary Matrix,
* Technical Report 88-942, October 1988,
* Department of Computer Science, Cornell University.
*/
float polar_decomp(HMatrix M, HMatrix Q, HMatrix S)
{
#define TOL 1.0e-6
HMatrix Mk, MadjTk, Ek;
float det, M_one, M_inf, MadjT_one, MadjT_inf, E_one, gamma, g1, g2;
mat_tpose(Mk, =, M, 3);
M_one = norm_one(Mk);
M_inf = norm_inf(Mk);
do
{
adjoint_transpose(Mk, MadjTk);
det = vdot(Mk[0], MadjTk[0]);
if (det == 0.0)
{
do_rank2(Mk, MadjTk, Mk);
break;
}
MadjT_one = norm_one(MadjTk);
MadjT_inf = norm_inf(MadjTk);
gamma = sqrt(sqrt((MadjT_one * MadjT_inf) / (M_one * M_inf)) / fabs(det));
g1 = gamma * 0.5f;
g2 = 0.5f / (gamma * det);
mat_copy(Ek, =, Mk, 3);
mat_binop(Mk, =, g1 * Mk, +, g2 * MadjTk, 3);
mat_copy(Ek, -=, Mk, 3);
E_one = norm_one(Ek);
M_one = norm_one(Mk);
M_inf = norm_inf(Mk);
} while (E_one > (M_one * TOL));
mat_tpose(Q, =, Mk, 3);
mat_pad(Q);
mat_mult(Mk, M, S);
mat_pad(S);
for (int i = 0; i < 3; i++)
{
for (int j = i; j < 3; j++)
{
S[i][j] = S[j][i] = 0.5f * (S[i][j] + S[j][i]);
}
}
return (det);
}
/******* Spectral Decomposition *******/
/* Compute the spectral decomposition of symmetric positive semi-definite S.
* Returns rotation in U and scale factors in result, so that if K is a diagonal
* matrix of the scale factors, then S = U K (U transpose). Uses Jacobi method.
* See Gene H. Golub and Charles F. Van Loan. Matrix Computations. Hopkins 1983.
*/
HVect spect_decomp(HMatrix S, HMatrix U)
{
HVect kv;
double Diag[3], OffD[3]; /* OffD is off-diag (by omitted index) */
double g, h, fabsh, fabsOffDi, t, theta, c, s, tau, ta, OffDq, a, b;
static char nxt[] = {Y, Z, X};
int sweep;
mat_copy(U, =, mat_id, 4);
Diag[X] = S[X][X];
Diag[Y] = S[Y][Y];
Diag[Z] = S[Z][Z];
OffD[X] = S[Y][Z];
OffD[Y] = S[Z][X];
OffD[Z] = S[X][Y];
for (sweep = 20; sweep > 0; sweep--)
{
float sm = static_cast<float>(fabs(OffD[X]) + fabs(OffD[Y]) + fabs(OffD[Z]));
if (sm == 0.0)
{
break;
}
for (int i = Z; i >= X; i--)
{
int p = nxt[i];
int q = nxt[p];
fabsOffDi = fabs(OffD[i]);
g = 100.0 * fabsOffDi;
if (fabsOffDi > AZ::Constants::FloatEpsilon)
{
h = Diag[q] - Diag[p];
fabsh = fabs(h);
if (fabsh + g == fabsh)
{
t = OffD[i] / h;
}
else
{
theta = 0.5 * h / OffD[i];
t = 1.0 / (fabs(theta) + sqrt(theta * theta + 1.0));
if (theta < 0.0)
{
t = -t;
}
}
c = 1.0 / sqrt(t * t + 1.0);
s = t * c;
tau = s / (c + 1.0);
ta = t * OffD[i];
OffD[i] = 0.0;
Diag[p] -= ta;
Diag[q] += ta;
OffDq = OffD[q];
OffD[q] -= s * (OffD[p] + tau * OffD[q]);
OffD[p] += s * (OffDq - tau * OffD[p]);
for (int j = Z; j >= X; j--)
{
a = U[j][p];
b = U[j][q];
U[j][p] -= static_cast<float>(s * (b + tau * a));
U[j][q] += static_cast<float>(s * (a - tau * b));
}
}
}
}
kv.x = static_cast<float>(Diag[X]);
kv.y = static_cast<float>(Diag[Y]);
kv.z = static_cast<float>(Diag[Z]);
kv.w = 1.0f;
return (kv);
}
/******* Spectral Axis Adjustment *******/
/* Given a unit Quaternernion, q, and a scale vector, k, find a unit Quaternernion, p,
* which permutes the axes and turns freely in the plane of duplicate scale
* factors, such that q p has the largest possible w component, i.e. the
* smallest possible angle. Permutes k's components to go with q p instead of q.
* See Ken Shoemake and Tom Duff. Matrix Animation and Polar Decomposition.
* Proceedings of Graphics Interface 1992. Details on p. 262-263.
*/
Quatern snuggle(Quatern q, HVect* k)
{
#define SQRTHALF (0.7071067811865475244f)
#define sgn(n, v) ((n) ? -(v) : (v))
#define swap(a, i, j) {a[3] = a[i]; a[i] = a[j]; a[j] = a[3]; }
#define cycle(a, p) if (p) {a[3] = a[0]; a[0] = a[1]; a[1] = a[2]; a[2] = a[3]; } \
else {a[3] = a[2]; a[2] = a[1]; a[1] = a[0]; a[0] = a[3]; }
Quatern p = { 0.0f, 0.0f, 0.0f, 1.0f };
float ka[4];
int i, turn = -1;
ka[X] = k->x;
ka[Y] = k->y;
ka[Z] = k->z;
if (ka[X] == ka[Y])
{
if (ka[X] == ka[Z])
{
turn = W;
}
else
{
turn = Z;
}
}
else
{
if (ka[X] == ka[Z])
{
turn = Y;
}
else if (ka[Y] == ka[Z])
{
turn = X;
}
}
if (turn >= 0)
{
Quatern qtoz, qp;
unsigned neg[3], win;
double mag[3], t;
static Quatern qxtoz = {0, SQRTHALF, 0, SQRTHALF};
static Quatern qytoz = {SQRTHALF, 0, 0, SQRTHALF};
static Quatern qppmm = { 0.5, 0.5, -0.5, -0.5};
static Quatern qpppp = { 0.5, 0.5, 0.5, 0.5};
static Quatern qmpmm = {-0.5, 0.5, -0.5, -0.5};
static Quatern qpppm = { 0.5, 0.5, 0.5, -0.5};
static Quatern q0001 = { 0.0, 0.0, 0.0, 1.0};
static Quatern q1000 = { 1.0, 0.0, 0.0, 0.0};
switch (turn)
{
default:
return (Qt_Conj(q));
case X:
q = Qt_Mul(q, qtoz = qxtoz);
swap(ka, X, Z);
break;
case Y:
q = Qt_Mul(q, qtoz = qytoz);
swap(ka, Y, Z);
break;
case Z:
qtoz = q0001;
break;
}
q = Qt_Conj(q);
mag[0] = (double)q.z * q.z + (double)q.w * q.w - 0.5;
mag[1] = (double)q.x * q.z - (double)q.y * q.w;
mag[2] = (double)q.y * q.z + (double)q.x * q.w;
for (i = 0; i < 3; i++)
{
neg[i] = (mag[i] < 0.0);
if (neg[i])
{
mag[i] = -mag[i];
}
}
if (mag[0] > mag[1])
{
if (mag[0] > mag[2])
{
win = 0;
}
else
{
win = 2;
}
}
else
{
if (mag[1] > mag[2])
{
win = 1;
}
else
{
win = 2;
}
}
switch (win)
{
case 0:
if (neg[0])
{
p = q1000;
}
else
{
p = q0001;
} break;
case 1:
if (neg[1])
{
p = qppmm;
}
else
{
p = qpppp;
} cycle(ka, 0);
break;
case 2:
if (neg[2])
{
p = qmpmm;
}
else
{
p = qpppm;
} cycle(ka, 1);
break;
}
qp = Qt_Mul(q, p);
t = sqrt(mag[win] + 0.5);
p = Qt_Mul(p, Qt_(0.0f, 0.0f, static_cast<float>(-qp.z / t), static_cast<float>(qp.w / t)));
p = Qt_Mul(qtoz, Qt_Conj(p));
}
else
{
float qa[4], pa[4];
unsigned lo, hi, neg[4], par = 0;
double all, big, two;
qa[0] = q.x;
qa[1] = q.y;
qa[2] = q.z;
qa[3] = q.w;
for (i = 0; i < 4; i++)
{
pa[i] = 0.0;
neg[i] = (qa[i] < 0.0);
if (neg[i])
{
qa[i] = -qa[i];
}
par ^= neg[i];
}
/* Find two largest components, indices in hi and lo */
if (qa[0] > qa[1])
{
lo = 0;
}
else
{
lo = 1;
}
if (qa[2] > qa[3])
{
hi = 2;
}
else
{
hi = 3;
}
if (qa[lo] > qa[hi])
{
if (qa[lo ^ 1] > qa[hi])
{
hi = lo;
lo ^= 1;
}
else
{
hi ^= lo;
lo ^= hi;
hi ^= lo;
}
}
else
{
if (qa[hi ^ 1] > qa[lo])
{
lo = hi ^ 1;
}
}
all = (qa[0] + qa[1] + qa[2] + qa[3]) * 0.5;
two = (qa[hi] + qa[lo]) * SQRTHALF;
big = qa[hi];
if (all > two)
{
if (all > big)/*all*/
{
{
int ii;
for (ii = 0; ii < 4; ii++)
{
pa[ii] = static_cast<float>(sgn(neg[ii], 0.5f));
}
}
cycle(ka, par)
}
else
{ /*big*/
pa[hi] = static_cast<float>(sgn(neg[hi], 1.0f));
}
}
else
{
if (two > big)/*two*/
{
pa[hi] = sgn(neg[hi], SQRTHALF);
pa[lo] = sgn(neg[lo], SQRTHALF);
if (lo > hi)
{
hi ^= lo;
lo ^= hi;
hi ^= lo;
}
if (hi == W)
{
hi = "\001\002\000"[lo];
lo = 3 - hi - lo;
}
swap(ka, hi, lo)
}
else
{ /*big*/
pa[hi] = static_cast<float>(sgn(neg[hi], 1.0f));
}
}
p.x = -pa[0];
p.y = -pa[1];
p.z = -pa[2];
p.w = pa[3];
}
k->x = ka[X];
k->y = ka[Y];
k->z = ka[Z];
return (p);
}
/******* Decompose Affine Matrix *******/
/* Decompose 4x4 affine matrix A as TFRUK(U transpose), where t contains the
* translation components, q contains the rotation R, u contains U, k contains
* scale factors, and f contains the sign of the determinant.
* Assumes A transforms column vectors in right-handed coordinates.
* See Ken Shoemake and Tom Duff. Matrix Animation and Polar Decomposition.
* Proceedings of Graphics Interface 1992.
*/
static void decomp_affine(HMatrix A, SAffineParts* parts)
{
HMatrix Q, S, U;
Quatern p;
float det;
parts->t = Qt_(A[X][W], A[Y][W], A[Z][W], 0);
det = polar_decomp(A, Q, S);
if (det < 0.0)
{
mat_copy(Q, =, -Q, 3);
parts->f = -1;
}
else
{
parts->f = 1;
}
parts->q = Qt_FromMatrix(Q);
parts->k = spect_decomp(S, U);
parts->u = Qt_FromMatrix(U);
p = snuggle(parts->u, &parts->k);
parts->u = Qt_Mul(parts->u, p);
}
static void spectral_decomp_affine(HMatrix A, SAffineParts* parts)
{
HMatrix Q, S, U;
float det;
parts->t = Qt_(A[X][W], A[Y][W], A[Z][W], 0);
det = polar_decomp(A, Q, S);
if (det < 0.0)
{
mat_copy(Q, =, -Q, 3);
parts->f = -1;
}
else
{
parts->f = 1;
}
parts->q = Qt_FromMatrix(Q);
parts->k = spect_decomp(S, U);
parts->u = Qt_FromMatrix(U);
}
// Decompose matrix to affine parts.
void AffineParts::Decompose(const Matrix34& tm)
{
SAffineParts parts;
Matrix44 tm44(tm);
HMatrix& H = *((HMatrix*)&tm44); // Treat HMatrix as a Matrix44.
decomp_affine(H, &parts);
rot = Quat(parts.q.w, parts.q.x, parts.q.y, parts.q.z);
rotScale = Quat(parts.u.w, parts.u.x, parts.u.y, parts.u.z);
pos = Vec3(parts.t.x, parts.t.y, parts.t.z);
scale = Vec3(parts.k.x, parts.k.y, parts.k.z);
fDet = parts.f;
}
// Spectral matrix decompostion to affine parts.
void AffineParts::SpectralDecompose(const Matrix34& tm)
{
SAffineParts parts;
Matrix44 tm44(tm);
HMatrix& H = *((HMatrix*)&tm44); // Treat HMatrix as a Matrix44.
spectral_decomp_affine(H, &parts);
rot = Quat(parts.q.w, parts.q.x, parts.q.y, parts.q.z);
rotScale = Quat(parts.u.w, parts.u.x, parts.u.y, parts.u.z);
pos = Vec3(parts.t.x, parts.t.y, parts.t.z);
scale = Vec3(parts.k.x, parts.k.y, parts.k.z);
fDet = parts.f;
}