Libnoise XNA翻译Perlin导致变形

Question

I've been looking at libraries to generate noise in XNA. Libnoise seemed like the most logical choice. The library is pretty easy to work and produces some great results. I'm having some trouble with generating additional sections though. The C++ documentation has a really nice function for this:

  utils::NoiseMap heightMap;
  utils::NoiseMapBuilderPlane heightMapBuilder;
  heightMapBuilder.SetSourceModule (myModule);
  heightMapBuilder.SetDestNoiseMap (heightMap);
  heightMapBuilder.SetDestSize (256, 256);
  heightMapBuilder.SetBounds (6.0, 10.0, 1.0, 5.0); //this one!
  heightMapBuilder.Build ();
//http://libnoise.sourceforge.net/tutorials/tutorial3.html

The XNA version doesn't work like this, and instead uses a translate function to "move" through the generated heightmap.

Translate.cs

/// <summary>
    /// Initializes a new instance of Translate.
    /// </summary>
    /// <param name="x">The translation on the x-axis.</param>
    /// <param name="y">The translation on the y-axis.</param>
    /// <param name="z">The translation on the z-axis.</param>
    /// <param name="input">The input module.</param>
    public Translate(double x, double y, double z, ModuleBase input)
        : base(1)
    {
        this.m_modules[0] = input;
        this.X = x;
        this.Y = y;
        this.Z = z;
    }

Usage

        perlin = new Perlin(zoom, 4, 0.2, 4, 1, QualityMode.Medium);
        Translate translate = new Translate(location.X, location.Y, 0, perlin);
        this.m_noiseMap = new Noise2D(200, 200, translate);
        this.m_noiseMap.GeneratePlanar(-1 * zoom, 1 * zoom, -1 * zoom, 1 * zoom, true);

Here is where the problem kicks in ; while it does translate the heightmap, it also distorts it. Which seems strange, because the perlin remains unmodified. I could have imagined changing the Z would cause the heightmap to change, but I'm only altering the X axis.

Any idea on this?

Answer 1

It looks like the main issue is what dimensions the heightmap is using to produce the results.

So, it's very vague as to what dimensions the heightmap builder is using as the elevation, especially after applying a projection...

It seems to me that X is controlling elevation (if you look at the ocean, it looks like you're literally raising the sea level). While this might not make much sense, it might be good to check the source and see what dimensions its actually using. 3D noise like this generally doesnt care which dimensions is which, as long as you make it cohere with your application.

Answer 2

I know this is an old thread, and I don't know what the translate is but I don't think you need it to generate different tiles.

Just use GeneratePlanar() function to offset the tile by X and Y units, and also make it relative to the zoom, so if you are zooming by 0.5, you move the offsets by factors of 0.5 for adjacent tiles

public void GeneratePlanar(double left, double right, double top, double bottom, bool seamless)

        // Initialize the noise map
        this.m_noiseMap = new Noise2D(resolution, resolution, moduleBase);
        this.m_noiseMap.GeneratePlanar(
        offsetX + 0 * 1/zoom, 
        offsetX + 1 * 1/zoom, 
        offsetY + 0 * 1/zoom,
        offsetY + 1 * 1/zoom);

Answer 3

I don't know about libnoise xna, but normal libnoise uses X and Z for the 2d height map. So you should translate X and Z instead of X and Y.