I don't know where I should have posted this, so I hope this is right.
I'm making a Javascript library for learning purposes, and for some of the animation functions I'm going to need the equation of a specific quadratic curve based on three inputs from, to and q.
Anyway I want to construct a quadratic equation (one that curves upwards not down) goes through three points, and I need it to be a method that I can write up into code (I will be using Javascript). I haven't gotten very far, but this is what I have planned out so far...
basically two numbers are input (from and to), d= tofrom
a = (0,0)
b = (d,0)
c = (p,q) p=d/2 q=Any input number, let's say 5
Then i need to get it into the form y=ax^2+bx+c but I'm not sure how to do this in a way that I can program it.
Cheers,
~Jamal
3 Replies  3375 Views  Last Post: 12 January 2013  03:51 PM
#1
How to make a quadratic curve equation given 3 coords?
Posted 18 September 2012  12:48 AM
Replies To: How to make a quadratic curve equation given 3 coords?
#2
Re: How to make a quadratic curve equation given 3 coords?
Posted 18 September 2012  02:37 AM
In other words, the roots are x=0 and x=d, and the top of the curve is at y=q.
Think about how you solve an equation to get the roots, you put it in the form:
You should now be able to work out a formula for an equation that passes through your required roots. To get it to pass through (d/2, q) you will need to multiply your equation by a constant. That should be fairly trivial to do.
Think about how you solve an equation to get the roots, you put it in the form:
0 = (x+a)(x+B)/>
You should now be able to work out a formula for an equation that passes through your required roots. To get it to pass through (d/2, q) you will need to multiply your equation by a constant. That should be fairly trivial to do.
#3
Re: How to make a quadratic curve equation given 3 coords?
Posted 12 November 2012  01:26 PM
You are trying to implement Bezier Curves with three points and you can use the well known De Casteljau's algorithm
http://en.wikipedia....u%27s_algorithm
here is the implementation in javascript
https://gist.github.com/1049745
http://en.wikipedia....u%27s_algorithm
here is the implementation in javascript
https://gist.github.com/1049745
#4
Re: How to make a quadratic curve equation given 3 coords?
Posted 12 January 2013  03:51 PM
I have a nonrecursive, noniterative way to do it. It isn't as nice as the recursive way, though. It involves simple matrix arithmetic.Dammit...the server isn't letting me upload!
EDIT: It became beautiful. Oh, and filesharing servers FTW: http://www.freefileh...venthreepoints2
EDIT: It became beautiful. Oh, and filesharing servers FTW: http://www.freefileh...venthreepoints2
This post has been edited by IceHot: 12 January 2013  05:11 PM
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