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add check against FLT_EPSILON/DBL_EPSILON for sqrt and division to avoid nan.

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add max_iterations count in svd as safety termination condition
This commit is contained in:
Erwin Coumans
2019-10-29 18:28:30 -07:00
parent 136607151e
commit 7bffbb2351
1 changed files with 37 additions and 11 deletions
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48
src/LinearMath/btImplicitQRSVD.h
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@@ -150,10 +150,14 @@ public:
btScalar d = a * a + b * b;
c = 1;
s = 0;
if (d != 0) {
btScalar t = btScalar(1.0)/btSqrt(d);
c = a * t;
s = -b * t;
if (d > SIMD_EPSILON) {
btScalar sqrtd = btSqrt(d);
if (sqrtd>SIMD_EPSILON)
{
btScalar t = btScalar(1.0)/sqrtd;
c = a * t;
s = -b * t;
}
}
}
@@ -167,7 +171,7 @@ public:
btScalar d = a * a + b * b;
c = 0;
s = 1;
if (d != 0) {
if (d > SIMD_EPSILON) {
btScalar t = btScalar(1.0)/btSqrt(d);
s = a * t;
c = b * t;
@@ -432,10 +436,11 @@ inline void polarDecomposition(const btMatrix2x2& A,
btScalar denominator = btSqrt(a*a+b*b);
R.c = (btScalar)1;
R.s = (btScalar)0;
if (denominator != 0) {
if (denominator > SIMD_EPSILON) {
/*
No need to use a tolerance here because x(0) and x(1) always have
smaller magnitude then denominator, therefore overflow never happens.
In Bullet, we use a tolerance anyway.
*/
R.c = a / denominator;
R.s = -b / denominator;
@@ -485,7 +490,10 @@ inline void singularValueDecomposition(
}
else {
btScalar tau = 0.5 * (x - z);
btScalar w = btSqrt(tau * tau + y * y);
btScalar val = tau * tau + y * y;
if (val > SIMD_EPSILON)
{
btScalar w = btSqrt(val);
// w > y > 0
btScalar t;
if (tau > 0) {
@@ -508,6 +516,13 @@ inline void singularValueDecomposition(
btScalar s2 = sine * sine;
sigma(0,0) = c2 * x - csy + s2 * z;
sigma(1,1) = s2 * x + csy + c2 * z;
} else
{
cosine = 1;
sine = 0;
sigma(0,0) = x;
sigma(1,1) = z;
}
}
// Sorting
@@ -558,9 +573,15 @@ inline btScalar wilkinsonShift(const btScalar a1, const btScalar b1, const btSca
{
btScalar d = (btScalar)0.5 * (a1 - a2);
btScalar bs = b1 * b1;
btScalar mu = a2 - copysign(bs / (btFabs(d) + btSqrt(d * d + bs)), d);
btScalar val = d * d + bs;
if (val>SIMD_EPSILON)
{
btScalar denom = btFabs(d) + btSqrt(val);
btScalar mu = a2 - copySign(bs / (denom), d);
// T mu = a2 - bs / ( d + sign_d*sqrt (d*d + bs));
return mu;
}
}
/**
@@ -749,15 +770,20 @@ inline int singularValueDecomposition(const btMatrix3x3& A,
btScalar beta_2 = B[1][2];
btScalar gamma_1 = alpha_1 * beta_1;
btScalar gamma_2 = alpha_2 * beta_2;
tol *= btMax((btScalar)0.5 * btSqrt(alpha_1 * alpha_1 + alpha_2 * alpha_2 + alpha_3 * alpha_3 + beta_1 * beta_1 + beta_2 * beta_2), (btScalar)1);
btScalar val = alpha_1 * alpha_1 + alpha_2 * alpha_2 + alpha_3 * alpha_3 + beta_1 * beta_1 + beta_2 * beta_2;
if (val > SIMD_EPSILON)
{
tol *= btMax((btScalar)0.5 * btSqrt(val), (btScalar)1);
}
/**
Do implicit shift QR until A^T A is block diagonal
*/
int max_count = 100;
while (btFabs(beta_2) > tol && btFabs(beta_1) > tol
&& btFabs(alpha_1) > tol && btFabs(alpha_2) > tol
&& btFabs(alpha_3) > tol) {
&& btFabs(alpha_3) > tol
&& count < max_count) {
mu = wilkinsonShift(alpha_2 * alpha_2 + beta_1 * beta_1, gamma_2, alpha_3 * alpha_3 + beta_2 * beta_2);
r.compute(alpha_1 * alpha_1 - mu, gamma_1);