直交座標から極座標への変換メモ ref: https://qiita.com/edo_m18/items/5d61f19512fb05f48501

Unity-C#

private void Convert(Color[] colors, int width, int height)
{
    int halfWidth = width / 2;
    int halfHeight = height / 2;

    Texture2D tex = new Texture2D(width, height);
    Color[] newColors = new Color[colors.Length];
    GameObject quad = GameObject.CreatePrimitive(PrimitiveType.Quad);
    quad.name = "PolarCoord";

    for (int y = 0; y < height; y++)
    {
        for (int x = 0; x < width; x++)
        {
            int dx = x - halfWidth;
            int dy = halfHeight - y;

            int X = (int)Mathf.Floor(Mathf.Atan2(dy, dx) * (width / 360f) * (180f / Mathf.PI));
            int Y = (int)Mathf.Floor(Mathf.Sqrt(dx * dx + dy * dy));

            int idx = (Y * width) + X;
            Color color = colors[idx];

            int newIdx = (y * width) + x;
            newColors[newIdx] = color;
        }
    }

    tex.SetPixels(newColors);
    tex.Apply();

    Renderer ren = quad.GetComponent<Renderer>();
    ren.material.mainTexture = tex;
}