# Bounce Expression on Python in Cinema 4D

 02 February 2013 WotS New Member portfolio Askhad Apishev Maykop, RU Bounce Expression on Python in Cinema 4D Hello. This is one of the most useful scripts for After Effects, that adds oscillatory train to any animated property. n = 0; if (numKeys > 0){ n = nearestKey(time).index; if (key(n).time > time){ n--; } } if (n == 0){ t = 0; }else{ t = time - key(n).time; } if (n > 0){ v = velocityAtTime(key(n).time - thisComp.frameDuration/10); amp = .5; freq = 4.0; decay = 2.0; value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t); }else{ value; } Script can be added as expression to any property move, size, rotation, opacity, color, etc - and influence this feature with the keys, adding oscillatory train in the end. So, I'm trying to write this script on Python in Cinema 4D. And here is what I got. import math import c4d #Welcome to the world of Python def main(): obj = doc.SearchObject("Test_Cube") track = obj.GetFirstCTrack() curve = track.GetCurve() numkeys = curve.GetKeyCount() n = 0 time = doc.GetTime() fps = doc.GetFps() curFrame = time.GetFrame(fps) lst = [] for i in range(0, numkeys): key = curve.GetKey(i).GetValue() keytime = curve.GetKey(i).GetTime().GetFrame(fps) lst.append(keytime) lstS = [] for i in range(0,len(lst)): sub = abs(lst-curFrame) lstS.append(sub) for i, j in enumerate(lstS): if j == min(lstS): MinInd = i nearestKey = lst[MinInd] for i, j in enumerate(lst): if j == nearestKey: nearestKeyIndex = i if numkeys > 0: n = nearestKeyIndex if nearestKey > curFrame: n = n-1 if n == 0: t = 0 else: t = curFrame - nearestKey lastKeyValue = curve.GetKey(numkeys-1).GetValue() previousKeyValue = curve.GetKey(numkeys-2).GetValue() curValue = curve.GetValue(time,fps) if n > 0: v = (lastKeyValue - previousKeyValue)*fps amp = 0.5 freq = 4 decay = 2 curValue + v*amp*math.sin(freq*t*2*3.14)/math.exp(decay*t) else: curValue In Cinema 4D there are no such functions as [I]nearestKey and velocityAtTime unlike After Effects. My script does not work in Cinema 4D. For writing it I used the Python tag. Compile says "No errors". This script is Executed. But not the desired effect. There is no change in the object's animation. I count on your help guys. P.S. I am sorry for my bad English share quote
 02 February 2013 littledevil Meh   portfolio Ferdinand Germany 1. Post your code in a readable format, either by using [kode][/kode] tags or better by providing a link like http://codepad.org/. At least I am unwilling to read your code in this form. 2. To get the closest key you have just to loop through your curve and get the best key match. 3. The velocity is the length of the vector CurVector - PrevVector. If you want the position velocity, cache the global position of your point(s) and then calculate the velocity with it. Edit : ok, the picture an be enlarged, still not an optimal solution for more complex code, when you might want to execute it for yourself. You main error seems to be that you never write your values back or do anything at all with them. curValue just sits there and does nothing. I also do not really understand, what you are trying to do with all loops and the mapping in your code, to get the closest key just loop once through your curve and get the best key.time/currenttime match. Last edited by littledevil : 02 February 2013 at 02:39 PM. share quote
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