skinning.py

from __future__ import division
import numpy as np

import sys
sys.path.append('/Users/mattjj/Dropbox/work/datta/renderer')
from MouseData import MouseData
m = MouseData('/Users/mattjj/Dropbox/work/datta/renderer/data/mouse_mesh_low_poly3.npz')
translations = m.joint_translations

def inv(E):
    out = E.copy()
    out[:-1,:-1] = E[:-1,:-1].T
    out[:-1,-1]  = E[:-1,:-1].T.dot(-E[:-1,-1])
    return out

out = np.zeros((5,4,4))
out[:,-1,-1] = 1.
def Es(angles):
    cosines = np.cos(angles)
    sines = np.sin(angles)
    for idx in range(5):
        cx, cy, cz = cosines[idx]
        sx, sy, sz = sines[idx]
        out[idx,:-1,:] = np.array(( (cy*cz,          -cy*sz,         -sy   , translations[idx,0]),
                                    (cx*sz-sx*sy*cz, cx*cz+sx*sy*sz, -sx*cy, translations[idx,1]),
                                    (sx*sz+sy*cx*cz, sx*cz-cx*sy*sz,  cx*cy, translations[idx,2]), ))
    return out


fixed_Es = Es(m.joint_rotations)
fixed_Ms = np.empty((5,4,4))
fixed_Ms[0] = inv(fixed_Es[0])
for idx in range(1,5):
    # cumulative right-product
    fixed_Ms[idx] = fixed_Ms[idx-1].dot(inv(fixed_Es[idx]))

changed_Ms = np.empty((5,4,4))
def get_Ms(angles):
    changed_Es = Es(angles)
    changed_Ms[0] = changed_Es[0]
    for idx in range(1,5):
        # cumulative left-product
        changed_Ms[idx] = changed_Es[idx].dot(changed_Ms[idx-1])
    return [fixed_M.dot(changed_M) for fixed_M, changed_M in zip(fixed_Ms, changed_Ms)]