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# The contents of this file are subject to the Mozilla Public License Version
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# The Original Code is the Python Computer Graphics Kit.
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# The Initial Developer of the Original Code is Matthias Baas.
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# $Id: motionpath.py,v 1.2 2006/01/27 07:51:02 mbaas Exp $
from cgkit.component import Component
from cgkit.slots import *
from math import *
# MotionPath
class MotionPath(Component):
"""Motion path.
"""
def __init__(self,
name = "MotionPath",
curve = None,
begintime = 0.0,
endtime = 1.0,
loop = False,
follow = False,
bank = False,
bankamplitude = 0.1,
auto_insert = True):
"""Constructor.
"""
Component.__init__(self, name=name, auto_insert=auto_insert)
self.curve = curve
self.begintime = begintime
self.endtime = endtime
self.loop = loop
self.follow = follow
self.bank = bank
self.bankamplitude = bankamplitude
self.transform_slot = ProceduralMat4Slot(self.computeTransform)
self.time_slot = DoubleSlot()
self.time_slot.addDependent(self.transform_slot)
self.addSlot("transform", self.transform_slot)
self.addSlot("time", self.time_slot)
# computeTransform
def computeTransform(self):
"""Procedural for the transform slot.
"""
# Determine the native curve parameter t...
time = self.time_slot.getValue()
len = self.curve.length()
s = (time-self.begintime)/(self.endtime-self.begintime)
if self.loop:
s %= 1.0
s *= len
if s<0:
s = 0.0
if s>len:
s = len
t = self.arcLenToCurveParam(s)
# Evaluate the curve
p, dp, d2p = self.curve.evalFrame(t)
up = vec3(0,0,1)
if self.follow:
try:
T = mat4().lookAt(p, p+dp, up)
except:
T = mat4().translation(p)
else:
T = mat4().translation(p)
if self.bank:
dp = dp.normalize()
dt = 0.001
dp_prev = self.curve.deriv(t-dt).normalize()
d2p = (dp-dp_prev)/dt
# Make the 2nd derivative orthogonal to the tangent...
len = d2p.length()
u = d2p.cross(dp)
d2p = dp.cross(u)
d2p = len*d2p.normalize()
if (dp.cross(up)*d2p<0):
len = -len
T = T*mat4().rotation(self.bankamplitude*len, vec3(0,0,1))
return T
# arcLenToCurveParam
def arcLenToCurveParam(self, s, eps=0.0001, maxiter=100):
"""Determine the native curve parameter for a given arc length.
"""
tmin, tmax = self.curve.paraminterval
totallen = self.curve.arcLen(tmax)
# Initial "guess"...
t = tmin+(s/totallen)*(tmax-tmin)
while maxiter>0:
F = self.curve.arcLen(t)-s
if abs(F)<=eps:
return t
dF = self.curve.deriv(t).length()
if abs(dF)<1E-12:
# TODO: do something
print "MotionPath: ************ dF==0 !!!"
dF = 1
t -= F/dF
maxiter -= 1
print "MotionPath: Maximum number of iterations reached (s=%f)"%s
return t
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