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+--- Thread: Normalize Zero Vector? (/thread-2059.html)
Normalize Zero Vector? - DiamondToaster - 07-17-2015
So, I've noticed that for a while, normalizing a zero-distance vector returns a nil value. Should this be fixed to return a zero vector? According to people on Stack Overflow, the normalized form of a zero vector is also a zero vector This would be useful so I don't have to check for nil values and use hackish workarounds.
http://stackoverflow.com/questions/722073/how-do-you-normalize-a-zero-vector
RE: Normalize Zero Vector? - NiLSPACE - 07-17-2015
When calling the Normalize function you normalize the vector you're calling the function on.. if that makes sense
RE: Normalize Zero Vector? - DiamondToaster - 07-18-2015
I know that, but as the documentation for the Vector3d class says: Changes this vector so that it keeps current direction but is exactly 1 unit long. FIXME: Fails for a zero vector. If you set the coordinates for a vector, let's say, Direction. If you set each of Direction's coordinates to 0 then call Direction:Normalize(), the distance and each component become NaN when they should stay at 0.
RE: Normalize Zero Vector? - NiLSPACE - 07-18-2015
Oh, it shouldn't be too hard to do that right?
x = (x == 0) ? 0 : (1 / x); y = (y == 0) ? 0 : (1 / y); z = (z == 0) ? 0 : (1 / z);
This code doesn't work.
RE: Normalize Zero Vector? - DiamondToaster - 07-19-2015
I just feel that it should be handled by the server since it's a core function of a 3D vector. The API also says it's a "FIXME:." I'll probably look into making a patch or something, it should be really easy.
RE: Normalize Zero Vector? - NiLSPACE - 07-19-2015
Simply changing this line to something like:
double Len = 1.0 / (Length() == 0) ? 0.0000000001 : Length();should work right?
RE: Normalize Zero Vector? - xoft - 07-19-2015
I think you should guide the optimizer to remove the double call to Length(), by storing it in a temporary variable.
RE: Normalize Zero Vector? - DiamondToaster - 07-20-2015
Maybe something like this?
I'm not sure how much of a performance impact an if statement and 3 divides will make.
inline void Normalize(void)
{
double Len = Length();
// If the length is zero, the vector cannot possibly have a direction.
if (Len == 0.0d)
{
x = static_case<T>(0);
y = static_case<T>(0);
z = static_case<T>(0);
return;
}
x = static_cast<T>(x / Len);
y = static_cast<T>(y / Len);
z = static_cast<T>(z / Len);
}
I guess this also applies to Vector3::NormalizeCopy().
RE: Normalize Zero Vector? - xoft - 07-20-2015
(updated your post to use the correct code tag)
Basically, yes, but you don't want to compare to zero exactly, you want to compare to an epsilon (abs(Len) < EPS) to accommodate for numerical inaccuracy.