Hello everyone,
I try to make a slerp between two quaternions.
I have a formula that works, but I encounter a problem with maya ...
This is my slerp function:
def slerp_quaternion(m_quaternion_1, m_quaternion_2, f_weight):
m_quaternion_1 = m_quaternion_1.normal()
m_quaternion_2 = m_quaternion_2.normal()
# If is equial return first quaternion
if m_quaternion_1.isEquivalent(m_quaternion_2):
return m_quaternion_1
# If the dot product is negative, the quaternions
# have opposite handed-ness and slerp won't take
# the shorter path. Fix by reversing one quaternion.
# dot = dot_product(m_quaternion_1, m_quaternion_2)
dot = dot_product(m_quaternion_1, m_quaternion_2)
if dot < 0.0:
m_quaternion_2.negateIt()
dot *= -1.0
# Weight Blend
f_scale_1 = 1.0 - f_weight
f_scale_2 = f_weight
# Get Quaternion median
dot = max(min(dot, 1.0), -1.0)
f_theta = math.acos(dot)
f_sin_theta = math.sin(f_theta)
f_scale_1 = math.sin(f_scale_1 * f_theta) / f_sin_theta
f_scale_2 = math.sin(f_scale_2 * f_theta) / f_sin_theta
# New Quaternion
a_new_values = []
for i in xrange(4):
a_new_values.append(lerp(m_quaternion_1[i], m_quaternion_2[i],
f_weight))
return pmc.datatypes.Quaternion(a_new_values[0], a_new_values[1],
a_new_values[2], a_new_values[3])
In Maya, if I take two quaternions from an MFnTransform (getRotation) and I
turn a transform on an axis I have:
- A dot > 0 between 0 ° and 180 °
- A dot < 0 if I am between 180 * and 270 *.
If I do this in a custom node since a matrix my dowry is always positive no
matter what happens ...
In Maya to get quaternion from a matrix you have to go through the
MTransformationMatrix. And that only changes the value of my quaternions
once I pass the 180 °.
Maya automatically reverse quaternion ? If is that, how i made a gool slerp
? ...
So, I also have a function to getter the quaternion since any matrix:
def quaternion_from_matrix(m_matrix):
w = math.sqrt(max(0, 1 + m_matrix(0, 0) + m_matrix(1, 1) + m_matrix(2,
2))) / 2.0
x = math.sqrt(max(0, 1 + m_matrix(0, 0) - m_matrix(1, 1) - m_matrix(2,
2))) / 2.0
y = math.sqrt(max(0, 1 - m_matrix(0, 0) + m_matrix(1, 1) - m_matrix(2,
2))) / 2.0
z = math.sqrt(max(0, 1 - m_matrix(0, 0) - m_matrix(1, 1) + m_matrix(2,
2))) / 2.0
x *= -1 if x * (m_matrix(2, 1) - m_matrix(1, 2)) >= 0.0 else 1
y *= -1 if y * (m_matrix(0, 2) - m_matrix(2, 0)) >= 0.0 else 1
z *= -1 if z * (m_matrix(1, 0) - m_matrix(0, 1)) >= 0.0 else 1
return OpenMaya.MQuaternion(x, y, z, w)
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