「uGUI/Texture2Dで描画するリアルタイム流体計算」 最終的なソースコード (http://tasogare-games.hatenablog.jp/entry/20150428/1430203599)

Main.cs

using UnityEngine;
using UnityEngine.UI;

public class Main : MonoBehaviour
{
    public RawImage raw;
    public int N = 64;
    public float diff = 0.0f;
    public float visc = 0.0f;
    public float force = 5.0f;
    public float source = 100.0f;

    private Texture2D _tex;
    private Color[] _colors;
    private Vector3 _pos0;
    private float[] _u, _u0, _v, _v0, _dens, _dens0;



    void Start()
    {
        if ((N & (N - 1)) != 0) Debug.LogError("定数Nは2の累乗にしてください");
        if (!raw) Debug.LogError("RawImageを指定してください");

        ClearData();
        
        _tex = new Texture2D(N, N, TextureFormat.RGB24, false);
        raw.color = Color.white;
        raw.texture = _tex;
    }

    void Update()
    {
        float dt = Time.deltaTime * 10f;

        GetFromUI(_dens0, _u0, _v0);
        FluidMath.VelStep(N, ref _u, ref _v, ref _u0, ref _v0, visc, dt);
        FluidMath.DensStep(N, ref _dens, ref _dens0, ref _u, ref _v, diff, dt);
        DrawDensity();
    }



    void ClearData()
    {
        int size = (N + 2) * (N + 2);

        _u = new float[size];
        _u0 = new float[size];
        _v = new float[size];
        _v0 = new float[size];
        _dens = new float[size];
        _dens0 = new float[size];
        _pos0 = Vector3.zero;
        _colors = new Color[N * N];

        for (int i = 0; i < size; i++)
        {
            _u[i] = _u0[i] = _v[i] = _v0[i] = _dens[i] = _dens0[i] = 0.0f;
        }
    }

    void GetFromUI(float[] d, float[] u, float[] v)
    {
        int i, j, k;
        int size = (N + 2) * (N + 2);

        for (i = 0; i < size; i++)
        {
            u[i] = v[i] = d[i] = 0;
        }

        if (Input.GetKeyDown("c")) ClearData();

        if (!Input.GetMouseButton(0) && !Input.GetMouseButton(1)) return;

        Vector3 pos = raw.transform.InverseTransformPoint(Input.mousePosition);
        i = Mathf.CeilToInt(pos.x + N * 0.5f);
        j = Mathf.CeilToInt(pos.y + N * 0.5f);

        if (i < 0 || i >= N || j < 0 || j >= N) return;
        k = FluidMath.IX(N, i, j);

        if (Input.GetMouseButton(0))
        {
            if (Input.GetMouseButtonDown(0))
            {
                _pos0 = pos;
                return;
            }

            u[k] = force * (pos.x - _pos0.x);
            v[k] = force * (pos.y - _pos0.y);
        }

        if (Input.GetMouseButton(1))
        {
            d[k] = source;
        }

        _pos0 = pos;
    }

    void DrawDensity()
    {
        float d;

        for (int i = 0; i < N; i++)
        {
            for (int j = 0; j < N; j++)
            {
                d = _dens[FluidMath.IX(N, i + 1, j + 1)];
                _colors[i + N * j] = new Color(d, d, d);
            }
        }

        _tex.SetPixels(_colors);
        _tex.Apply();
    }
}