Thanks for the piece of code!

After some more thought, I came out with the following idea: a "standard" sigmoïd method works, but it is not easy to control tune it. Actually I just would like to build a function that looks like a smoothed stair:

1       /-        slow stop
|   /-/
0-/      1       slow start


satisfying f(0)=0, f(0.5)=0.5 and f(1)=1, and any other constraint letting me say "at T I want the cam to have done distance D". Finally, it seems the best is to "build" the function using an interpolation (I will use bernstein, that works well), where each keypoint represent a D=f(T) constraint. One can really "model" the camera behaviour with details.

Cheers,
Martin

Hi,

Thanks for these suggestions. One thing I forgot to tell: I want to control the LENGTH of each animation. Up to now I check the frame rate before starting any animation, to determine the number of necessary key points required to have the choosen duration. Unless I misunderstood your suggestion, it seems to me that your solutions requires little thinking to determine acceleration and other parameters to control the number of steps.

I was thinking about using a function to shifts linear steps:
 
(1) compute the linear interpolation of the n intermediate steps. First and last point make distance D.
(2) convert each point to polar, to have a distance information from start.
(3) then each point Pi should be at distance= D*i/n from start.

(4) For this next step, the best is to normalize in [0;1], so consider distance=i/n. We will update each polar point with:
      P.radius = f(P.radius)
I thus need a function y=f(x) that gives y=0 for x=0 and y=1 for x=1, and that let me "stretch" the animation timing easily:
      f(x)=x^2 makes a simple accelerating move, x^3,4,5 will be more "sharp": slower at the beginning and faster at the end.
      f(x)=-(x-1)^2+1 makes the contrary acceleration: fast at the beginning, slow at the end. One must have an even pow value.

so I better need a normalized sigmoïd function. I will tell you if I find a good candidate for this method

It is a little mangled, but allows to customize speed variation easily! Maybe there are some other more straightforward methods.

Cheers,
Martin

Hi!
I have implemented the method that indicates the full polar coordinate (with angle in [0;2*PI]) of an input coordinate, which could be mouse-bob in your case.
Search for Coord2d.fullPolar() here: http://code.google.com/p/jzy3d/source/browse/branches/0.8.1/src/api/org/jzy3d/maths/Coord2d.java

I use it a lot and it works as expected.
Cheers,
Martin

Hi folks,
I have a 2d scene, and do camera moves between two given points by simply defining N equal intermediate steps along the line formed by the start and stop point.
I'd like to accelerate at the beginning and slow down at the end. Do you have any suggestions to do that smartly?
Cheers,
Martin

Hi all,
I guess this place is better to advertise than the "shared code" section of this forum:
Jzy3d is an open source library that let you easily plot simple 3d for reviewing scientifical data:
http://code.google.com/p/jzy3d/
Cheers,
Martin

Thanks for your support! Yes Jzy3d goes further with great new features still under development. Feel free to follow http://twitter.com/#!/jzy3d to get notified on new features.
Cheers,
Martin

Mm, I thought it was for graphics, but you're right, we're not on java-graphics.org
Cheers,
Martin

That's what I did :/
I will tell you if I find the reason.
Cheers,
Martin

Hi all,
First time I see this forum, and I guess it's worth sharing a project with all of you
http://code.google.com/p/jzy3d/
Cheers,
Martin

Hi,
When running the applet from the browser, the path does not start after the two clicks.
When building and running from sources, the pathfind returns a null path at the following call

GridPath aPath = pathfinding.getPath(mouse.getStart(), mouse.getEnd(), draw.getMap());

Any suggestion to have the demo running?! It seems great!
Cheers
Martin