Graphviz crossing edges - graphviz

Question

I am trying to avoid the crossing of the lines between 20->40 and 30->70. Does anyone know how to do this? I am using single points to straighten out the edges but I would have expected the rendering engine to avoid these edges to overlap. Here is my dot code:
digraph {
graph [splines="ortho", nodesep = "1", overlap = false];
node [shape=rectangle, color=lightgrey, style=filled ];
10
20
30
40
50
60
70
80
90
node[shape=none, width=0, height=0 label=""];
edge[dir=none];
{rank=same;
p1->10
10->p2
}
p1->20
p2->30
{rank=same;
p3->40
40->p4
}
p3->50
p4->60
{rank=same;
p5->70
70->p6
}
p5->80
p6->90
20->40
30->70
}
I wanted to post an image, but stackoverflow does not allow me to do this... You can see what I mean when you copy the code into: http://stamm-wilbrandt.de/GraphvizFiddle/
I really appreciate your help on this!

Answer 1

You could give graphviz a hint by adding an invisible edge between p4 an dp5:
{
rank=same;
p3 -> 40;
40 -> p4;
p4 -> p5 [style=invis]; // new invisible edge
p5 -> 70;
70 -> p6;
}
If you are not able to add invisible edges (dynamic graph generation), make sure nodes which are part of a subgraph do appear first within the subgraph, and therefore avoid upfront node definitions.
In this example, I removed the node definitions in the beginning of the script and inlined the style of the elbow-joint nodes.
Here's the GraphvizFiddle
digraph {
graph [splines="ortho", nodesep = "1", overlap = false];
node [shape=rectangle, color=lightgrey, style=filled ];
//node[shape=none, width=0, height=0, label=""];
edge[dir=none];
{
rank=same;
p1[shape=none, width=0, height=0, label=""];
p2[shape=none, width=0, height=0, label=""];
p1->10
10->p2
}
p1->20
p2->30
{
rank=same;
p3[shape=none, width=0, height=0, label=""];
p4[shape=none, width=0, height=0, label=""];
p3->40
40->p4
}
p3->50
p4->60
{
rank=same;
p5[shape=none, width=0, height=0, label=""];
p6[shape=none, width=0, height=0, label=""];
p5->70
70->p6
}
p5->80
p6->90
20->40
30->70
}