I'm trying to make my own vector module, and for the most part it works (as far as I know), but in trying to add rotation I'm getting unexpected results.
I'm not 100% sure whether the results are right, and my expectations are wrong, or vice versa.
I'm rotating a 3D vector by an angle 'a', and then rotating it by 'a'. But it doesn't end up the same as it started.
The vector rotation code is on lines 166 through to 181.
I know and don't mind that it assumes the vector is 3D.
Can anyone please help?
Vector Rotation
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Vector Rotation
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Re: Vector Rotation
precision issues? (seems kind of excessive though...)
Re: Vector Rotation
The problem is due to modification of origin vector during computation (origin vector = result vector).
For the rotation around xaxis, the formula must be :
x' = x
y' = cos * y + sin *z
z' = cos * z  sin * y
Or in fact you do y = ...., so you change y value for the z' computation and the the z result is false.
You can rewrite you code as this :
For the rotation around xaxis, the formula must be :
x' = x
y' = cos * y + sin *z
z' = cos * z  sin * y
Or in fact you do y = ...., so you change y value for the z' computation and the the z result is false.
You can rewrite you code as this :
Code: Select all
 MATRIX ROTATION SHORTCUT

function Vector:rotate(a, b, c)
local outcome = self:copy()
local x,y,z
 xaxis
y,z = outcome.y, outcome.z
outcome.y = y * math.cos(a) + z * math.sin(a)
outcome.z = z * math.cos(a)  y * math.sin(a)
 yaxis
x,z = outcome.x, outcome.z
outcome.x = x * math.cos(b)  z * math.sin(b)
outcome.z = z * math.cos(b) + x * math.sin(b)
 zaxis
x,y = outcome.x,outcome.y
outcome.x = x * math.cos(c) + y * math.sin(c)
outcome.y = y * math.cos(c)  x * math.sin(c)
return outcome
end
Re: Vector Rotation
Ah, of course, that makes perfect sense.
Thank you very much for pointing out my mistake.
Thank you very much for pointing out my mistake.
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