Matrix components

[macklebee]

Can someone explain how the scale/rotation are saved in the 4x4 matrix?

 

I have this as the result from using GMFDump:

	MESH
Data starts at: 28
	{
28	- 		Matrix: 
	1.00000000, 0.000000000, 0.000000000, 0.000000000
	0.000000000, -1.34358856e-007, 0.999999940, 0.000000000
	0.000000000, -0.999999940, -1.34358856e-007, 0.000000000
	0.000000000, 7.72592878, 0.000000000, 1.00000000

 

and this is what is shown when using the model viewer:

 

I assume I have to perform some quaternion/euler conversion for the rotation values... but in any case it doesn't appear that other than the position listed in the last line that the rotation and scale are in any kind of order?

[Flexman]

An Identity Matrix is...

mat.ix=1 ; mat.iy=0 ; mat.iz=0 ; mat.iw=0
mat.jx=0 ; mat.jy=1 ; mat.jz=0 ; mat.jw=0
mat.kx=0 ; mat.ky=0 ; mat.kz=1 ; mat.kw=0
mat.tx=0 ; mat.ty=0 ; mat.tz=0 ; mat.tw=1

Scale for XYZ is ix, jy, kz

Position XYZ is tx , ty , tz

 

The tricky part is rotation. I tried to write a quick function that I thought would demonstrate it but I kept getting an exception error LOL. I'll come back to it if I figure out why. I wonder if Leadwerks does something funny for rotations.

[Josh]

Ah, matrix math. That matrix looks right.

 

Line 1: The local x axis points at 1,0,0

Line 2: The local y axis points at roughly 0,0,1

Line 3: The local z axis points at roughly 0,-1,0

 

So the object is pointing down, which makes sense with a euler rotation of 90,-180,180. That's where gimbal lock sets in, so the yaw and roll are a little funny.

 

The scale should be 1,1,1 and it's only because of floating point imprecision that it's not. That happens all the time and isn't a problem.