155 lines
3.7 KiB
C#
155 lines
3.7 KiB
C#
using System;
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using UnityEngine;
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namespace UltimateWater
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{
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public static class ButterflyFFTUtility
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{
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private static void BitReverse(int[] indices, int N, int n)
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{
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for (int i = 0; i < N; i++)
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{
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int num = 0;
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int num2 = indices[i];
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for (int j = 0; j < n; j++)
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{
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int num3 = 1 & num2;
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num = (num << 1) | num3;
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num2 >>= 1;
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}
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indices[i] = num;
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}
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}
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private static void ComputeWeights(Vector2[][] weights, int resolution, int numButterflies)
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{
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int num = resolution >> 1;
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int num2 = 1;
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float num3 = 1f / (float)resolution;
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for (int i = 0; i < numButterflies; i++)
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{
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int num4 = 0;
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int num5 = num2;
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Vector2[] array = weights[i];
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for (int j = 0; j < num; j++)
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{
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int num6 = num4;
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int num7 = 0;
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while (num6 < num5)
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{
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float f = MathF.PI * 2f * (float)num7 * (float)num * num3;
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float num8 = Mathf.Cos(f);
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float num9 = 0f - Mathf.Sin(f);
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array[num6].x = num8;
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array[num6].y = num9;
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array[num6 + num2].x = 0f - num8;
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array[num6 + num2].y = 0f - num9;
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num6++;
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num7++;
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}
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num4 += num2 << 1;
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num5 = num4 + num2;
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}
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num >>= 1;
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num2 <<= 1;
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}
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}
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private static void ComputeWeights(float[][] weights, int resolution, int numButterflies)
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{
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int num = resolution >> 1;
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int num2 = 2;
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float num3 = 1f / (float)resolution;
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for (int i = 0; i < numButterflies; i++)
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{
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int num4 = 0;
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int num5 = num2;
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float[] array = weights[i];
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for (int j = 0; j < num; j++)
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{
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int num6 = num4;
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int num7 = 0;
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while (num6 < num5)
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{
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float f = MathF.PI * 2f * (float)num7 * (float)num * num3;
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float num8 = Mathf.Cos(f);
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float num9 = 0f - Mathf.Sin(f);
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array[num6] = num8;
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array[num6 + 1] = num9;
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array[num6 + num2] = 0f - num8;
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array[num6 + num2 + 1] = 0f - num9;
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num6 += 2;
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num7++;
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}
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num4 += num2 << 1;
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num5 = num4 + num2;
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}
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num >>= 1;
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num2 <<= 1;
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}
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}
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private static void ComputeIndices(int[][] indices, int resolution, int numButterflies)
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{
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int num = resolution;
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int num2 = 1;
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for (int i = 0; i < numButterflies; i++)
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{
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num >>= 1;
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int num3 = num << 1;
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int num4 = 0;
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int num5 = 0;
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int num6 = num3;
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int[] array = indices[i];
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for (int j = 0; j < num2; j++)
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{
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int num7 = num5;
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int num8 = num4;
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int num9 = 0;
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while (num7 < num6)
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{
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array[num7] = num8;
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array[num7 + 1] = num8 + num;
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array[num9 + num6] = num8;
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array[num9 + num6 + 1] = num8 + num;
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num7 += 2;
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num9 += 2;
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num8++;
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}
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num5 += num3 << 1;
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num6 += num3 << 1;
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num4 += num3;
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}
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num2 <<= 1;
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}
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BitReverse(indices[numButterflies - 1], resolution << 1, numButterflies);
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}
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public static void ComputeButterfly(int resolution, int numButterflies, out int[][] indices, out Vector2[][] weights)
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{
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indices = new int[numButterflies][];
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weights = new Vector2[numButterflies][];
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for (int i = 0; i < numButterflies; i++)
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{
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indices[i] = new int[resolution << 1];
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weights[i] = new Vector2[resolution];
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}
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ComputeIndices(indices, resolution, numButterflies);
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ComputeWeights(weights, resolution, numButterflies);
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}
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public static void ComputeButterfly(int resolution, int numButterflies, out int[][] indices, out float[][] weights)
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{
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indices = new int[numButterflies][];
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weights = new float[numButterflies][];
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for (int i = 0; i < numButterflies; i++)
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{
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indices[i] = new int[resolution << 1];
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weights[i] = new float[resolution << 1];
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}
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ComputeIndices(indices, resolution, numButterflies);
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ComputeWeights(weights, resolution, numButterflies);
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}
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}
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}
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