extern int minhtree;
extern int maxhtree;

void make_tree(ManualMapVoxelManipulator &vmanip, v3s16 p0,
		bool is_apple_tree, INodeDefManager *ndef)
{
	MapNode treenode(ndef->getId("mapgen_tree"));
	MapNode leavesnode(ndef->getId("mapgen_leaves"));
	MapNode applenode(ndef->getId("mapgen_apple"));

	s16 trunk_h = myrand_range(minhtree, maxhtree);
	v3s16 p1 = p0;
	for(s16 ii=0; ii<trunk_h; ii++)
	{
		if(vmanip.m_area.contains(p1))
			vmanip.m_data[vmanip.m_area.index(p1)] = treenode;
		p1.Y++;
	}

	// p1 is now the last piece of the trunk
	p1.Y -= 1;
...