What you are doing is a common mistake:


for (int x = 0; x < world.GetLength(0) - 1; x++)
{
for (int y = 0; y < world.GetLength(1) - 1; y++)
{
diamond[x,y] = Noise.Generate(x, y);
}
}


Perlin noise is generated by interpolating values that are generated at integer boundaries. If you sample the noise at integer coordinates, then, you won't get the smooth in-between values you are expecting; what you get instead is basically white noise, as you have discovered.

Something like this might get you better results:

float frequency=1.0f/(float)world.GetLength(0);
for (int x = 0; x < world.GetLength(0) - 1; x++)
{
for (int y = 0; y < world.GetLength(1) - 1; y++)
{
diamond[x,y] = Noise.Generate((float)x*frequency (float)y*frequency);
}
}


You do need to tweak the exact mapping by playing with the frequency value.

A good rule of thumb for choosing frequency is that a Perlin function has 1 feature per unit, where a feature is a hill or valley. So if you want 1 hill, use a frequency equal to your world size dimension. If you want more hills, use a larger value.

As far as using noise in a sane manner to generate terrain, you might check out this article.

I don't know that I'd say that was a larger problem. It doesn't matter how many layers of detail you stack on; unless you do your mapping correctly, all you're adding is ever smaller detail that still gets lost in the mapping. The first layer defines the over-all feature size, successive layers are detail. Fix the mapping first, then add more detail.

Agreed on the integer problem, it gets so many people. Also potentially agreed about octaves. But I wonder if there's an even more fundamental problem. From your screenshot it looks like you're using 2D Perlin noise. Often people use 2D Perlin noise to generate a heightfield for a 3D world. For a side-scrolling platformer I would expect you'd only want 1D Perlin noise, and then to use those values as the height of your hills. I would think that 2D Perlin noise is only applicable if you want to allow mining (like Minecraft/Infiniminer) or if you want to allow caves. Even then, raw 2D Perlin noise is generally not useful as it would create islands floating in space. Instead you'd use 1D Perlin noise to create the general contour of the land, and then subtract 2D Perlin noise from anything that appears under that curve to make caves.

1D noise is useful if you want to do just simple rolling terrain. 2D is useful if you want to do things like caves and overhangs. Again, I refer you to this article written by JTippetts. It's pretty interesting, and I think you can do some cool stuff with it. I hope he doesn't mind me linking to his images, but I think they really help to make the point. (JTippetts, if you don't want me linking to them, let me know and I'll remove them.) The premise of it is this: a function differentiates between ground and sky (anything below a certain level is ground, anything above is sky). Normally this threshold is a flat line at a certain level (Y=0, for example). A 1D noise function is used to push the ground level up or down by a certain amount.

Here is the basic ground/sky:


The white part (which is hard to see, of course, on the white background here) is the ground.

The article talks about using a 1D function to perturb the ground, which would end up looking like this:



It also talks about using a 2D function to perturb it, which would look like this:



The second one, imo, is "cooler" looking, but it does result in floating islands.

The article also talks about using a second function to impose caves upon the terrain:



It's really an interesting article, and while it is written sort of centric to his own library, the idea of it should be usable with any library.

Very interesting larspensjo, but keep in mind that the OP will have to subtract 1 dimension from all your advice as they are making a 2D side scroller rather than a 3D world.