View Full Version : Trajectory Calculation (math help please)

09-09-2005, 12:16 PM
I am pretty good at math, really I am. But I would appreciate it if someone could point me in the right direction with this word problem. In VT-Edit I have 16 PNG files that need to move off the screen at different speeds while getting larger. I am using a JPEG that contains all 16 images as a positioning reference and I have animated the JPEG to yield what I believe will be the final position. Next, I position file1.png over the file1.png image in the JPEG at 00:00:00.00. Now, I fast forward to 02.07 where only a small portion of file1.png is visible and I line that up with the JPEG. From this point to continue the trajectory off the screen I have to guess on the size, x, & y positions because I don't have enough image left for an adequate alignment. I am able to line everything up at 02.27 but how can I maintain the trajectory until 03.27 (or some other time)? Even more helpful would assistance with the following: using the starting and ending points of the animated alignment JPEG and the starting point of file1.png how can enlarge and move the PNG at the same rate as the JPEG?
Here is the actual data for file1.png:
X -210.87
Y -29.4
Size (%) 30.00
X -360.77
Y 30.83
Size (%) 38.50
Here is the data for the JPEG positioning reference file:
X 1.37
Y -27.38
Size (%) 47.94
X -72.35
Y 33.58
Size (%) 64.81
00:00:12.00 (final position of JPEG)
X -394.28
Y 299.81
Size (%) 138.5
Anything from tips to formulas will be greatly appreciated. Thank You. Dan.

09-09-2005, 02:34 PM
Without looking at the numbers you posted I would say that you could go to the spline view and add a node for x, y and size at the point in time you wish to continue on till. Now all you need to do is make sure the spline is straight and delete the center node. You should not need the center node but if you are not exact it will cause a slight blip, by deleting it you would avoid this.


09-09-2005, 08:14 PM
Thanks for the response, Ivan. The challenge is that I am going to a point in time that is off the screen, and I need to figure out what that point is. One thing that I neglected to mention is that all of my 16 objects that move off the screen are moving with a background image. The background image moves and grows and the 16 objects move and grow with the background. But the 16 objects need to be separate because they fade out one at a time. All I need to do is keep sixteen objects moving and growing in sync with a background image until all but the background are off screen. Thanks again for the response; I really appreciate it. Dan.

Jim Capillo
09-09-2005, 08:31 PM
Are you using 4.5? If so, I think what you need to do is shrink the positioner window so you can see the overscan area - then you can select "see all layers" and then get the positioning in the right aspect ratio and size at the end point of the object movement.

You can then save it in the Toolshed and apply it to the other frames within the pic - then just adjust the flight path of each different pic and you should be done.

Zooming in and out on the positioner window should make things real easy and minimize the need for math......

09-09-2005, 08:47 PM
I understand that you are moving them to off screen but the duration must still go beyond the last keyframe you can make visually in positioner. If you open the Spline control and display the splines you will see that there is an angle from the first to the last and then it flatlines to the end of the clip. If this is not the case, the clip is not long enough to do what you want, extend it. Now where it flatlines you can place an additional keyframe and match the angle. This will work if your clip is the correct length because the angle of the splines equals the direction and the slope equals the speed. As long as the one that you are trying to match is moving in a constant speed and direction you should have no trouble mapping the motion off screen, no math required.