MPH in Tempo
9 messages in this thread
I am doing a courtroom animation reconstructing a car accident. I want to use
the TEMPO routine to adjust the speed of the vehicles involved. I think it
should be possible to make the vehicle, setting up its path and setting the
following: From point A to point B the car was going 55 mph, at point B the
brakes were applied (where the reconstructionist has measured the skid marks to
start). Then use TEMPO to figure out how to animate the area from point B (55
mph) to point C (point of impact where I know from my reconstructionist
information the speed of the vehicle would have been 44 mph. And have the
vehicle stop completely at point C (the point of impact). I set up the movement
by setting a constant velocity for the car of 55 mph. Applying that, I noted
the frame where the car passed over point B. I go into TEMPO and using the
velocity curve add a point at that frame at 55 mph. Here's where I am lost. I
know where the point of impact was ( I have the distance set up from point B to
point C with the models already) How do I tell TEMPO where (or should I say
when) I need the car to be going 44 mph?
Is this description confusing. This is really driving me nuts. Any help is
greatly appreciated. In a nutshell I need to set tempo up to make the car go
from A to B at 55, then decelerate from 55 to 44 by the time the model reaches
C.
Paul Kakert
For example:
Paul,
I'm sorry for the delay in getting a response back to you re your Tempo
question, but things have been busy. Here's Rolf's response:
————————————————————————–
This one is slightly tricky. It's a similar problem to the base ball an bat
(the reason why we put in time segments in the velocity editor) but sort of the
inverse problem.
Instead of trying to be at a certain place at a certain time, You're trying to
be at a certain place at certain velocity.
First, set up the path as you would expect (probably with a key at points A, B,
and C). Make sure there are plenty of frames in the animation (path), scale
time if necessary.
Go into TEMPO and enter the velocity curve editor. Set the velocity curve to be
flat at 55 mph for the entire animation. Click OK to apply it (make sure fit to
path is NOT on).
Now go into the preview dialog to see at which frame the car passes point B.
We'll call this frame f.
Now go back into the velocity editor and set the start of the active segment to
frame f and place a node there at 55mph (Make sure the end of the segment is
the last frame). Add another node somewhere between the previous node and the
last node at 45mph.
Switch edit mode to 'Move Point' and click on the node you just made. Now what
you want to do is move this node horizontally (leaving it 45 mph) to get the
'New Track Length' to equal the 'Original Track Length'. When you get it, click
OK. Again, make sure 'Auto Fit To Track On Exit' is OFF.
That should do it.
Another approach is to actually figure out the time it would take to travel the
remaining distance, BC. If your velocity is going to be linear across BC then
your average velocity is (55mph + 45mph)/2 or 50mph. The distance from B to C
can be found by setting the active segment in the edit velocity dialog to start
at the frame that B is on and end on the last frame. It is then the value
labeled 'Original Track Length', call it d. The time, t, then is just d miles /
50 mph = t hours. You want this in frames so convert the hours to seconds and
then multiply by your frame rate. To find the frame to place the third node at,
add your result to f.
If you still have problems, make sure 1) you have plenty of extra frames. Add a
whole bunch of frames, you can delete the excess when you finish. 2) The path
is actually created to scale. 3DS doesn't have a unit setting for miles so set
units to feet and make sure the path is actually the right length.
PMJI
>>Make sure there are plenty of frames in the animation (path)<<
Does this mean adding extra frames onto the end of the animation were nothing
happens so that if the active segment gets longer it won't be truncated?
The tab key doesn't seem to affect the motion constraint arrow in tempo like it
does in 3DS it would be helpfull to have some kind of motion constraint if
there isn't one already.
ME
Yup. Add extra frames to the animation.
– G
Thanks,
The tempo Ipas took a little getting used to but it is probobly the IPAS that I
have used most often since purchasing #6 and #7.
ME
<First, set up the path as you would expect (probably with <a key at points A,
B, and C). Make sure there are plenty <of frames in the animation (path), scale
time if necessary.
<Go into TEMPO and enter the velocity curve editor. Set the <velocity curve to
be flat at 55 mph for the entire <animation. Click OK to apply it (make sure
fit to path is <NOT on).
<Now go into the preview dialog to see at which frame the <car passes point B.
We'll call this frame f.
<Now go back into the velocity editor and set the start of <the active segment
to frame f and place a node there at <55mph (Make sure the end of the segment
is the last <frame). Add another node somewhere between the previous <node and
the last node at 45mph.
<Switch edit mode to 'Move Point' and click on the node you <just made. Now
what you want to do is move this node <horizontally (leaving it 45 mph) to get
the 'New Track <Length' to equal the 'Original Track Length'. When you get <it,
click OK. Again, make sure 'Auto Fit To Track On Exit' <is OFF.
This is the response you sent me to my message on using tempo. Here's what I
have done.
I did what you indicated. Set the path of the car and added key grames at point
A, B and C. In tempo I set to 55 mph constant. Then I noted where the car
crossed points a and b. (38 and 71 respectively) Set velocity curve to active
segment start at 38. Added a point at 38 at 55 mph. Added another point at 71
going 44 mph (speed at point of initial impact which occurs at frame 71).
You then told me to move this 44 mph point horizontally to set the new track
length = to original. Moving it horizontally didn't change new length at all. I
had to add another point between C and the end fram and move them to 0 mph
(moving both hor. & vert) to get new track = to original.
Everything seems to have worked out OK. Just wanted to tell you what I wound up
doing differently to see if you told me wrong, or if I ran into a different
problem then you thought.
Interested in hearing more from you. Thanks for the help.
Paul
I'm glad you worked it out for yourself. Typing about this stuff is not
exactly the most intuitive way to communicate about it… that's for sure.
– G
Thanks again for the jump start helping me figure out my tempo questions.
Paul
You're welcome.
– G