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using System;
using System.Collections.Generic;
using System.Text;

namespace libTerrain
{
    partial class Channel
    {
        /// <summary>
        /// Flattens the area underneath rx,ry by moving it to the average of the area. Uses a spherical mask provided by the raise() function.
        /// </summary>
        /// <param name="rx">The X coordinate of the terrain mask</param>
        /// <param name="ry">The Y coordinate of the terrain mask</param>
        /// <param name="size">The size of the terrain mask</param>
        /// <param name="amount">The scale of the terrain mask</param>
        public void Flatten(double rx, double ry, double size, double amount)
        {
            FlattenFast(rx, ry, size, amount);
        }

        private void FlattenSlow(double rx, double ry, double size, double amount)
        {
            // Generate the mask
            Channel temp = new Channel(w, h);
            temp.Fill(0);
            temp.Raise(rx, ry, size, amount);
            temp.Normalise();
            double total_mod = temp.Sum();

            // Establish the average height under the area
            Channel newmap = new Channel(w, h);
            newmap.map = (double[,])map.Clone();

            newmap *= temp;

            double total_terrain = newmap.Sum();
            double avg_height = total_terrain / total_mod;

            // Create a flat terrain using the average height
            Channel flat = new Channel(w, h);
            flat.Fill(avg_height);

            // Blend the current terrain with the average height terrain
            // using the "raised" empty terrain as a mask
            Blend(flat, temp);

        }

        private void FlattenFast(double rx, double ry, double size, double amount)
        {
            int x, y;
            double avg = 0;
            double div = 0;

            int minX = Math.Max(0, (int)(rx - (size + 1)));
            int maxX = Math.Min(w, (int)(rx + (size + 1)));
            int minY = Math.Max(0, (int)(ry - (size + 1)));
            int maxY = Math.Min(h, (int)(ry + (size + 1)));

            for (x = minX; x < maxX; x++)
            {
                for (y = minY; y < maxY; y++)
                {
                    double z = size;
                    z *= z;
                    z -= ((x - rx) * (x - rx)) + ((y - ry) * (y - ry));

                    if (z < 0)
                        z = 0;

                    avg += z * amount;
                    div += z;
                }
            }

            double height = avg / div;

            for (x = minX; x < maxX; x++)
            {
                for (y = minY; y < maxY; y++)
                {
                    double z = size;
                    z *= z;
                    z -= ((x - rx) * (x - rx)) + ((y - ry) * (y - ry));

                    if (z < 0)
                        z = 0;

                    Set(x, y, Tools.linearInterpolate(map[x, y], height, z));
                }
            }
        }

        public void Flatten(Channel mask, double amount)
        {
            // Generate the mask
            Channel temp = mask * amount;
            temp.Clip(0, 1); // Cut off out-of-bounds values

            double total_mod = temp.Sum();

            // Establish the average height under the area
            Channel map = new Channel(w, h);
            map.map = (double[,])this.map.Clone();

            map *= temp;

            double total_terrain = map.Sum();
            double avg_height = total_terrain / total_mod;

            // Create a flat terrain using the average height
            Channel flat = new Channel(w, h);
            flat.Fill(avg_height);

            // Blend the current terrain with the average height terrain
            // using the "raised" empty terrain as a mask
            Blend(flat, temp);
        }
    }
}