Slow speed the closer to ground level(Math)

Update method for entities(The method called every tick or so to update an entity)?
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I have a class extending EntityHorse and would like to know what the update method is.
1.8 - 1.9 Just give me ideas and I'll try to find the correct awnser.

I need this to change a custom Entities gravity(Can I override a gravity method or do I have to override move?)

>Awnser>
For 1.9 it's n and I simply set motionY to -x.
Note: Thanks for the optimization mythbusterma!
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New Question

So instead of putting these threads to waste Ima change my question!

I would like to go from 0.9 to 0.4 when I go from block 14 above land to right on the surface.

I know a bit confusing I'll upload an image of what I mean in a bit.



Somthing like this?

Any nice way I can see the curve(Like shown above) of my system?

I have so far

Code:

int i = world.getHighestBlockYAt(new BlockPosition(this.locX, this.locY, this.locZ)).getY();
double floatDec = ((this.locY - i) / 100 + 0.4);
System.out.println(floatDec);
if (this.locY - i <= 14)
{
    this.motY = -floatDec;
    return;
}
this.motY = -0.9;

I can do math, but figuring out the solution . . . nope!

NOTE> Img is hosted on my site so don't expect it to stay up long>

EDIT by Moderator: merged posts, please use the edit button instead of double posting.