2D Terrain generation with controlled variations

Question

Well, I'm trying to create a simple endless runner and -this may sound repetitive- I'm searching for ways to generate the terrain. The game will only have 3 types of ground tiles, ascending, descending and plain, and it should look (somewhat) like this:

So, what I want to say is that the terrain can only vary 1 unit of height.

I first thought of perlin noise, but I haven't found any information about restricting height variations. I've also thought about choosing randomly between the three posible tiles, but I still want that "natural randomness" that perlin noise can produce (very high hills, deep valleys, etc)

Any idea on how to procede?

Thanks! And please excuse my english.

Answer 1

You can still use Perlin noise. You simply need to constrain the random value to three values. Depending on how you're generating the noise, you'll get a value between -1 and 1, or 0 and 1. Whatever you have, just divide it by three, and place your tiles based on that.

float range = Perlin.max - Perlin.min
float value = Perlin.GetValue(xCoord)

if(value < range * (1/3))
   placeDecending()
else if (value < range * (2/3))
   placeFlat()
else
   placeAccending()

Essentially you're just taking the range of random values you can get from Perlin noise, and splitting them into three categories:

• Less than 1/3
• Between 1/3 and 2/3
• Greater than 2/3

This gives you the benefit of gradient noise, while also constraining the output to three tile types.

Answer 2

You can also set a target height to move towards, with smaller target height variations in between. Then you can have a sort of rolling hills effect where stuff still gets generally higher or lower as desired.

This is a great use case for recursion where you can tweak the parameters of each step to get different spacings.