Mapping noise to sphere surface

Question

I'm attempting to create a sphere with terrain (aka planet). I managed to procedurally create an icosahedron, and I am able to subdivide it (yay), but now I'm stuck on terrain.

My current idea was to create a Perlin like "3D Noise Field" and sample density where each of the spheres vertices fall (as a height-map value). this way i should be able to tweak the noise (add octaves, etc) to roughen the "NoiseField" and thus the spheres surface.

pseudo example and result:

public void Terrain(float Scale)
{
    if (Scale < 0.01) return;

    List<Vector3> terrain = new List<Vector3>();
    for ( int i = 0; i < surface.vertices.Count; i++)
    {
        Vector3 vert = sphere.verts[i];
        Vector3 direction = vert.normalized;
        Vector3 newpoint = vert * Sample3DNoise(direction, Scale);
        terrain.Add(newpoint);
    }

    //this line replaces the original shape!        
    surface.vertices = terrain;

    Debug.Log("terrain Update");
}

public float Sample3DNoise(Vector3 point, float scale)
{
    //Vector3 direction = point.normalized;

    float u = point.normalized.x * scale;
    float v = point.normalized.y * scale;
    float w = point.normalized.z * scale;

    //poor attempt at 3d noise field
    //PerlinNoise(float, float );
    float x = Mathf.PerlinNoise(u , 0f);
    float y = Mathf.PerlinNoise(0f, v);
    float z = Mathf.PerlinNoise(u , v);

    //the average of the coords, returns "density at this point"
    return (x + y + z) / 3;
}

edit:

so while it appears i was able to achieve this, it's is clearly not the "terrain on surface of sphere" look I was aiming for. Any suggestions on how can I change the "noise field" so my surface is more planet like? or how else can i achieve this?

Answer 1

the answer was simple enough

Vector3 vector = original[i] + ((normal * noise) * amplitude);

basically i want to take the "original vert" and add "some noise in the correct direction" and scale by amplitude.

i ended up changing quite a bit of the project, but if anyone's curious it pretty much breaks down too...

    public void UpdateNoise(/* int layer,*/ float amplitude, float period)//, float frequency)
{
    List<Vector3> original  = Octaves[Octaves.Count - 2];//input verts
    List<Vector3> octave    = new List<Vector3>();

    for ( int i = 0; i < original.Count; i++)
    {
        Vector3 normal = original[i].normalized;
        float u = (normal.x * period);
        float v = (normal.y * period);
        float noise = Mathf.PerlinNoise(u, v);
        Vector3 vector = original[i] + ((normal * noise) * amplitude);

        octave.Add(vector);
    }        
    this.vertices = octave;//output verts
    //Octaves[Octaves.Count - 1] = octave;
}

Answer 2

It seems to me that if you want more of a planetary terrain effect, you would add the modifier to the original vert instead of multiplying them and change your scale value to a number that is a small percentage of the sphere's radius. Good luck.