[Request] Create a Interpret function for UpVector, FrontVector and CoordSystem

[alsed]

EDIT:
The first time I posted this I assumed that the fbx files could have axis system on the domain 0-2 or 1-3.
I was mistaken, the axis data for every fbx is in between 0-2.
But even if this is not a problem, a clear distinction between semantic data and raw data is useful.

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Currently there is a problem with the parse of UpVector, since FBX scenes can be defined by the 0-2 domain, implemented by Blender or the original 1-3 defined by the Autodesk SDK.
parsed by a 0-2 domain (implemented by Blender) or the original 1-3 definition by the original SDK.

The problem lies in combining the raw data from the axes with the semantic interpretation of that data:
UpAxis is not the same as UpVector.
FrontAxis is not the same as FrontVector (which is actually a base parity).
And CoordAxis is definitely not the same as CoordSystem.

if GlobalSettings just copy the raw data, then UpVector, FrontVector y CoordSystem could be constructed elsewhere:

// everything is an int
		get_property("UpAxis", UpAxis, int, toInt);
		get_property("UpAxisSign", UpAxisSign, int, toInt);
		get_property("FrontAxis", FrontAxis, int, toInt);
		get_property("FrontAxisSign", FrontAxisSign, int, toInt);
		get_property("CoordAxis", CoordAxis, int, toInt);
		get_property("CoordAxisSign", CoordAxisSign, int, toInt);

// the same change in the GlobalSettings constructor

A solution for this is to create a new function, (e.g. "InterpretAxisSystem"), that takes the raw axis data and construct the axis system.

Then, the problem with UpVector domain being 0-2 like in Blender, or 1-3 in the SDK, should be easily solved:

[nem0]

Hi, I'm testing with https://github.com/ufbx/ufbx/tree/master/data and it seems it's actually consistent in 0-2 range. If it's true, we could simply convert the axis to enums. Do you have any fbx file where this would not work?

[alsed]

I was mistaken. I thought the files could contain raw data in 0-2 or 1-3 format.
This is not the case. All FBX files are in 0-2 format, but then Autodesk SDK parses UpVector in 1-3 format.

Nonetheless, an interpreter function will allow Frontvector and Coordystem to be correctly reconstructed.

EDIT:

The FBX SDK defines in FbxAxisSystem:

enum  	EUpVector { eXAxis = 1, eYAxis = 2, eZAxis = 3 }
enum  	EFrontVector { eParityEven = 1, eParityOdd = 2 }
enum  	ECoordSystem { eRightHanded, eLeftHanded }

UpVector could be maintained without changes to UpAxis, or be interpreted into a 1-3 enum.

FrontVector can be interpreted constructing this rule:

If the up axis is X, the remain two axes will be Y And Z, so the ParityEven is Y, and the ParityOdd is Z ; If the up axis is Y, the remain two axes will X And Z, so the ParityEven is X, and the ParityOdd is Z; If the up axis is Z, the remain two axes will X And Y, so the ParityEven is X, and the ParityOdd is Y.

CoordSystem can be interpreted for example:

// Create normalized Vec3 from UpAxis, FrontAxis and CoordAxis

bool isRightHanded(const ofbx::Vec3 coord, const ofbx::Vec3 up, const ofbx::Vec3 front)
{
    ofbx::Vec3 cross = coord.cross(up);
    double dot = cross.dot(front);
    return dot > 0.0;
}