move along the line, curve and trajectory

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uncertaint

move along the line, curve and trajectory

in General Discussion • Other • 1 year ago

I am interested in following video,

http://www.guardian.co.uk/news/datablog/video/2012/jan/12/high-speed-2-hs2-rail-britain-mapped-animation?fb=native

I don't know how make the movement along the curve or some trajectory like "train", basicly, I tried to move point "like" curvy, but if I have specific line, I want the particles going alone this line, only I can get jumping behavior...not so smooth...I want the train.....

please (;-;) someone tell me how can I do it?

Replies(4)

mbraendle

Re: move along the line, curve and trajectory

1 year ago

For example, if you have drawn your trajectory with curve() segments you can interpolate along the curve with curvePoint() and a parameter t that is between 0 and 1 and that you increase stepwise. The same is also possible with Bezier curves. See Processing reference for those methods. So for small step widths of t, you should obtain a smooth motion.

One problem is to know the length of the curve segment, so that the step width of t can be adjusted accordingly. Of course, this depends on the parameters that were chosen for the curve. Unfortunately, I don't know a method for the curve() and bezier() implementations that returns this length.

Another problem is that you may have multiple segments of varying length on your map; then you should interpolate of course on the whole trajectory, but calculate the t values for each segment individually. As long we don't have a good estimate for the length, this might be a tricky business. (Of course there is always the option to vary t slowly and to approximate the length by summing up the distances between the current and the previous position; but this is cumbersome. Anyway, in the Processing implementation of the Catmull-Rom and Bezier splines, the functional form is known, so it should be possible for Processing to do integration internally.)

As an illustration you may see this on our library navigator map.

Click the map and type key n, then you will see all possible paths stored with the map. You see that the path segments are straight lines and have different lengths. Type n again to hide them.

Then choose a topic at the left (for example "Ab initio Methods"), then click the sign post button. The shortest path to the highlighted shelf with this topic is calculated (from the entrance) using Dijkstra's algorithm and displayed. If there is change of direction, a curve is interpolated instead of an edge. The path is interpolated with steps as described above (using an assumed step width of 60 cm in real world), segment-wise. That's why some segments show higher density than others.

Ale_

Re: move along the line, curve and trajectory

1 year ago

There´s an excellent tutorial on Bezier curves by Pomax:
http://processingjs.nihongoresources.com/bezierinfo
There you can find a lot of further information on the issues commented by mbraendle. Btw, nice navigator... :-)
· Ale

mbraendle

Re: move along the line, curve and trajectory

1 year ago

Thanks, excellent tutorial indeed!

uncertaint

Re: move along the line, curve and trajectory

1 year ago

Hi Mbraendle & Ale

Thank you so much for your information, Sorry for the late reply, I thought if I could work it out, I can post a nice move.

the website looks amazing!(both library navigator map and Bezier curves by Pomax. ..but very difficult for me(f~"~) (my poor math..><...)

library project is very similar to what I am doing, just for my own research.

I still can't understand how to manager with Bezier curves, when I ask the question(1 month ago ) , I can't event make a class..... now, much better..., I can do some small things with Daniel's code of "Path Following" <http://www.shiffman.net> ,

then, I have more trouble with class now... question post on class with Array or Arraylist from "loadStrings"

without loading the right path I can't work on "following".

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