How should I use this 1D perlin noise function?

Question

I'm trying to create a terraria like terrain with SDL2 and C++. For generating the terrain I'm trying to use the 1D noise function from here: https://github.com/SRombauts/SimplexNoise

It's pretty basic and only takes a x value. I've been messing around with it for a while but can't work out what to pass into the function as the x value. I first tried passing just the x value of the column I'm finding the noise for. This just returned 0 every time. Next I tried passing a value between 0 and 1, so I passed it x / width. This sort of worked, but the wider I made the terrain, the more spaced out it became.

Hope you understand, what I do give the function for the x value? Thanks in advance.

Answer 1

What Pikalek said is absolutely true about the return value, but the workaround he suggest is not very good.

Instead of adding a random offset, you should divide the current x position with a cobstant value. Let's call this value "smoothness". Higher smoothness means smokther terrain:

float smoothness = 20;
float height = 20; // Max height of terrain
for (float x = 0; x < COLUMN_MAX; x++) {
    float val = SimplexNoise::noise(x / smoothness) * height;
    // Stuff
}

Answer 2

The function documentation explicitly says:

@return Noise value in the range[-1; 1], value of 0 on all integer coordinates

Since the column number is an integer coord, passing it as input will always give 0 as output. An easy way around that is to add a constant decimal offset to the column number:

// seed RNG however you need
randomOffset = ((float) rand() / (RAND_MAX));

// do other setup as needed

// iterate over columns getting a noise value for each
for(int a=0; a<COLUMN_MAX; a++){
   float noiseValue = SimplexNoise::noise(a + randomOffset);

   // use noise value for the current column
}