Creating a Path

[Leper]

How do you create a destined path for an object to follow?

If I were to draw by freehand a path, how would I get an object to follow that exact path?

Seeing as how I can think of many ways it could be done, what do you think would be most efficient?

[Gnatinator]

A lot of developers I know take advantage of bezier curves. Just plot a few points and you get some perfectly smooth paths I've never used them myself, but I would recommend looking into them.

There are probably a million other ways to do it (depending on what you need the paths for)

[FlySim]

Ignoring timing, the simplist method is just to digitize a bunch
of points along the path and store them in a list.
(0,0)
(1,4)
(2,5)
...
But digitizing is a pain. So the next simplest is to use linear interpolation.
Digitize the ends of straight lines and use this equation to move between
the points:

p = p0 + fract*(p1-p0)

But you have to digitize alot of straight segments to approximate a curve,
so you could use some sort of spline function. One of the most simple is the
Hermite cubic spline. To use it you need two end points p0, p1 and two
tangents at the end points tan0, tan1

p = A + B*fract + C*fract*fract + D*fract*fract*fract
where
A = p0
B = tan0
C = 3*(p1-p0) - 2*tan0 - p0
D = 2*(p0-p1) + tan0 + tan1

Using this spline, all you have to digitize is a small number of key points
and the tangents at these points. There are methods to compute those
tangents.

Hope this helps....

[svero]

One way I've done it is record a macro in a paint program as I lay down points using a line drawing tool. Then I take the macro and edit out the points from it to create the data file. Then I load the points into my game and interpolate through them creating an array of equidistant points for an object to follow.

- S

[ggambett]

From the FAQ :

1. Do not post requests for [...] help with your code or how to code it - These subjects are well covered by other forums such as Gamedev.net and Ludumdare.

[svero]

I think I might actually be inclined to change up that faq a little.. seems like a reasonable place to post this kind of question. I guess the fear is that we're going to end up with a ton of specific basic coding questions, which really would be better handled on another site. But I quite like the detailed technical discussion of how to implement things like paths, dirty rects etc... specific to game development.