one method from a c# class

Deformer.cs

    private void FlattenVolume() {
        float flattenToY = Mathf.Lerp(deformerCollider.bounds.min.y, deformerCollider.bounds.max.y, flattenTo);   
        float flattenHeight = Coord.WorldHeightToTerrainHeight(flattenToY, terrain);

        foreach (Vertex v in this.localHeightMap.localHeightmapVertices) {
            if (v.insideDeformerCollider || (!v.insideDeformerCollider && this.flattenArea)) {
                if (v.areaZ < this.terrainArea.terrainHeights.GetLength(0) || v.areaX < this.terrainArea.terrainHeights.GetLength(1)) {
                    this.terrainArea.terrainHeights[v.areaZ, v.areaX] = flattenHeight;
                }                
            }
        }
    }