public void Execute(int index)
{
// Use cols=x and rows=y for height data
int x = JobA.Col(index, hDim);
int y = JobA.Row(index, hDim);
float rx = (float)x / div;
float ry = (float)y / div;
int ix = Mathf.FloorToInt(rx);
int iy = Mathf.FloorToInt(ry);
float sfracx = (float)x / (float)(hDim - 1);
float sfracy = (float)y / (float)(hDim - 1);
float fracx = (float)(x - ix * div) / div;
float fracy = (float)(y - iy * div) / div;
float scaledHeight = 0;
// Bicubic sample small height map for base terrain elevation
x1 = TerrainHelper.CubicInterpolator(baseHeightValue[JobA.Idx(0, 3, sd)], baseHeightValue[JobA.Idx(1, 3, sd)], baseHeightValue[JobA.Idx(2, 3, sd)], baseHeightValue[JobA.Idx(3, 3, sd)], sfracx);
x2 = TerrainHelper.CubicInterpolator(baseHeightValue[JobA.Idx(0, 2, sd)], baseHeightValue[JobA.Idx(1, 2, sd)], baseHeightValue[JobA.Idx(2, 2, sd)], baseHeightValue[JobA.Idx(3, 2, sd)], sfracx);
x3 = TerrainHelper.CubicInterpolator(baseHeightValue[JobA.Idx(0, 1, sd)], baseHeightValue[JobA.Idx(1, 1, sd)], baseHeightValue[JobA.Idx(2, 1, sd)], baseHeightValue[JobA.Idx(3, 1, sd)], sfracx);
x4 = TerrainHelper.CubicInterpolator(baseHeightValue[JobA.Idx(0, 0, sd)], baseHeightValue[JobA.Idx(1, 0, sd)], baseHeightValue[JobA.Idx(2, 0, sd)], baseHeightValue[JobA.Idx(3, 0, sd)], sfracx);
baseHeight = TerrainHelper.CubicInterpolator(x1, x2, x3, x4, sfracy);
scaledHeight += baseHeight * baseHeightScale;
// Bicubic sample large height map for noise mask over terrain features
x1 = TerrainHelper.CubicInterpolator(lhm[JobA.Idx(ix, iy + 0, ld)], lhm[JobA.Idx(ix + 1, iy + 0, ld)], lhm[JobA.Idx(ix + 2, iy + 0, ld)], lhm[JobA.Idx(ix + 3, iy + 0, ld)], fracx);
x2 = TerrainHelper.CubicInterpolator(lhm[JobA.Idx(ix, iy + 1, ld)], lhm[JobA.Idx(ix + 1, iy + 1, ld)], lhm[JobA.Idx(ix + 2, iy + 1, ld)], lhm[JobA.Idx(ix + 3, iy + 1, ld)], fracx);
x3 = TerrainHelper.CubicInterpolator(lhm[JobA.Idx(ix, iy + 2, ld)], lhm[JobA.Idx(ix + 1, iy + 2, ld)], lhm[JobA.Idx(ix + 2, iy + 2, ld)], lhm[JobA.Idx(ix + 3, iy + 2, ld)], fracx);
x4 = TerrainHelper.CubicInterpolator(lhm[JobA.Idx(ix, iy + 3, ld)], lhm[JobA.Idx(ix + 1, iy + 3, ld)], lhm[JobA.Idx(ix + 2, iy + 3, ld)], lhm[JobA.Idx(ix + 3, iy + 3, ld)], fracx);
noiseHeight = TerrainHelper.CubicInterpolator(x1, x2, x3, x4, fracy);
x1 = TerrainHelper.CubicInterpolator(noiseHeightMultiplierMap[JobA.Idx(0, 3, sd)], noiseHeightMultiplierMap[JobA.Idx(1, 3, sd)], noiseHeightMultiplierMap[JobA.Idx(2, 3, sd)], noiseHeightMultiplierMap[JobA.Idx(3, 3, sd)], sfracx);
x2 = TerrainHelper.CubicInterpolator(noiseHeightMultiplierMap[JobA.Idx(0, 2, sd)], noiseHeightMultiplierMap[JobA.Idx(1, 2, sd)], noiseHeightMultiplierMap[JobA.Idx(2, 2, sd)], noiseHeightMultiplierMap[JobA.Idx(3, 2, sd)], sfracx);
x3 = TerrainHelper.CubicInterpolator(noiseHeightMultiplierMap[JobA.Idx(0, 1, sd)], noiseHeightMultiplierMap[JobA.Idx(1, 1, sd)], noiseHeightMultiplierMap[JobA.Idx(2, 1, sd)], noiseHeightMultiplierMap[JobA.Idx(3, 1, sd)], sfracx);
x4 = TerrainHelper.CubicInterpolator(noiseHeightMultiplierMap[JobA.Idx(0, 0, sd)], noiseHeightMultiplierMap[JobA.Idx(1, 0, sd)], noiseHeightMultiplierMap[JobA.Idx(2, 0, sd)], noiseHeightMultiplierMap[JobA.Idx(3, 0, sd)], sfracx);
float noiseHeightMultiplier = TerrainHelper.CubicInterpolator(x1, x2, x3, x4, sfracy);
scaledHeight += noiseHeight * noiseHeightMultiplier;
// Additional noise mask for small terrain features at ground level
// small terrain features' height scale should depend on climate of map pixel
float extraNoiseScaleTopLeft = extraNoiseScaleBasedOnClimateTopLeft;
float extraNoiseScaleTopRight = extraNoiseScaleBasedOnClimateTopRight;
float extraNoiseScaleBottomLeft = extraNoiseScaleBasedOnClimateBottomLeft;
float extraNoiseScaleBottomRight = extraNoiseScaleBasedOnClimateBottomRight;
//float extraNoiseScale = (1.0f - sfracx) * (1.0f - sfracy) * extraNoiseScaleTopLeft +
// (sfracx) *(1.0f - sfracy) * extraNoiseScaleTopRight +
// (1.0f - sfracx) * (sfracy) * extraNoiseScaleBottomLeft +
// (sfracx) * (sfracx) * extraNoiseScaleBottomRight;
float extraNoiseScale = TerrainHelper.BilinearInterpolator(extraNoiseScaleTopLeft, extraNoiseScaleBottomLeft, extraNoiseScaleTopRight, extraNoiseScaleBasedOnClimateBottomRight, sfracx, sfracy);
//float extraNoiseScale = TerrainHelper.BilinearInterpolator(extraNoiseScaleBottomLeft, extraNoiseScaleTopLeft, extraNoiseScaleBasedOnClimateBottomRight, extraNoiseScaleTopRight , sfracx, sfracy);
//float extraNoiseScale = extraNoiseScaleBasedOnClimate;
//// prevent seams between different climate map pixels
//if (x <= 0 || y <= 0 || x >= hDim - 1 || y >= hDim - 1)
//{
// extraNoiseScale = defaultExtraNoiseScale;
//}
int noisex = mapPixelX * (hDim - 1) + x;
int noisey = (MapsFile.MaxMapPixelY - mapPixelY) * (hDim - 1) + y;
float lowFreq = TerrainHelper.GetNoise(noisex, noisey, 0.3f, 0.5f, 0.5f, 1);
float highFreq = TerrainHelper.GetNoise(noisex, noisey, 0.9f, 0.5f, 0.5f, 1);
scaledHeight += (lowFreq * highFreq) * extraNoiseScale;
// Clamp lower values to ocean elevation
if (scaledHeight < scaledOceanElevation)
{
scaledHeight = scaledOceanElevation;
}
// Set sample
float height = Mathf.Clamp01(scaledHeight / maxTerrainHeight);
heightmapData[index] = height;
}