Vector Question

gilman

I am wondering about how different parts of vectors are accessed. What I mean is how does fuse know which piece of my vector I am asking about. Specifically, I have a vector called playerpos = {400,300}

print(playerpos.x) prints 400. Is x always assigned to the first value? Does it continue indefinately through x,y,z....? If so what comes after z

Thanks
-Gil

pianofire

Believe it or not w! (I think it was for width)

You can also access them using r,g,b and a or array indices [0] to [3]

Something

I often wonder the same. There are times when I make something and don't understand how Fuze can understand, but it does. Or it doesn't understand something which I think it should.

spikey

@pianofire I did not know about r,g,b. Now, I can improve some code, where i used x,yz, w on color vectors😂

PB____

I knew rgba and xyzw, but I wasn't aware of the array indices, which is good to know, because I sometimes use vectors in my own functions for other properties than color or position :) (for example, for padding, border and margin)

Something

@pianofire Can the rotation of an object be stored in a vector, or is it only position?

Gothon

@Something There are no built in functions to store a rotation in a 4 element Fuze vector. However I have had much success using a quaternion representation to store 3D rotations in Fuze's 4 element vectors.

I use the following code as a blackbox to store and manipulate rotations as vectors in all my shared programs:

// Concatenate 2 Quaternions (rotations)
Function QuatMult(a, b)
    vector c = a.w * b + b.w * a + Cross(a, b)
    c.w -= Dot(a, b)
Return c
// Rotate a vector v by a unit quaternion q
Function QuatRot(q, v) Return QuatMult(QuatMult(q, v), {-q.x, -q.y, -q.z, q.w})

Function AxisAngleToQuat(Axis, Angle)
    float Mag = Length(Axis)
    If Mag > 0 Then
        Axis *= Sin(Angle / 2) / Mag
        Axis.w = Cos(Angle / 2)
    Else
        Axis = {0, 0, 0, 1}
    EndIf
Return Axis

You can create them from an axis-angle representation, combine them in any order and apply them to any point/vector.

To apply the rotation to a 3D model in Fuze, you can call ObjectPointAt() to reset the rotation followed by RotateObject() with an axis-angle representation.

I do this in my 'Rubik's Cube Toy' program, using the formula:

axis = {q.x, q.y, q.z}
mag = Length(axis)
angle = ATan2(mag, q.w) * 2

while taking care to not call RotateObject() if mag is 0.

All of these formulas I obtained from Wikipedia:
https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation

DomDom

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