Determines if and how node overlaps should be removed

type: string | bool, default: true

Nodes are first enlarged using the sep attribute. If true , overlaps are retained. If the value is "scale", overlaps are removed by uniformly scaling in x and y. If the value converts to "false", and it is available, Prism, a proximity graph-based algorithm, is used to remove node overlaps. This can also be invoked explicitly with overlap=prism. This technique starts with a small scaling up, controlled by the overlap_scaling attribute, which can remove a significant portion of the overlap. The prism option also accepts an optional non-negative integer suffix. This can be used to control the number of attempts made at overlap removal. By default, overlap="prism" is equivalent to overlap="prism1000". Setting overlap="prism0" causes only the scaling phase to be run.

If Prism is not available, or the version of Graphviz is earlier than 2.28, "overlap=false" uses a Voronoi-based technique. This can always be invoked explicitly with "overlap=voronoi".

If overlap="scalexy", x and y are separately scaled to remove overlaps.

If overlap="compress", the layout will be scaled down as much as possible without introducing any overlaps, obviously assuming there are none to begin with.

**N.B.**The remaining allowed values of overlap correspond to algorithms which, at present, can produce bad aspect ratios. In addition, we deprecate the use of the "ortho*" and "portho*".

If the value is "vpsc", overlap removal is done as a quadratic optimization to minimize node displacement while removing node overlaps.

If the value is "orthoxy" or "orthoyx", overlaps are moved by optimizing two constraint problems, one for the x axis and one for the y. The suffix indicates which axis is processed first. If the value is “ortho”, the technique is similar to “orthoxy” except a heuristic is used to reduce the bias between the two passes. If the value is "ortho_yx", the technique is the same as "ortho", except the roles of x and y are reversed. The values "portho", "porthoxy", "porthoxy", and "portho_yx" are similar to the previous four, except only pseudo-orthogonal ordering is enforced.

If the layout is done by neato with mode=“ipsep”, then one can use overlap=ipsep. In this case, the overlap removal constraints are incorporated into the layout algorithm itself. N.B. At present, this only supports one level of clustering.

Except for fdp and sfdp, the layouts assume overlap="true" as the default. Fdp first uses a number of passes using a built-in, force-directed technique to try to remove overlaps. Thus, fdp accepts overlap with an integer prefix followed by a colon, specifying the number of tries. If there is no prefix, no initial tries will be performed. If there is nothing following a colon, none of the above methods will be attempted. By default, fdp uses overlap="9:prism". Note that overlap="true", overlap="0:true" and overlap="0:" all turn off all overlap removal.

By default, sfdp uses overlap="prism0".

Except for the Voronoi and prism methods, all of these transforms preserve the orthogonal ordering of the original layout. That is, if the x coordinates of two nodes are originally the same, they will remain the same, and if the x coordinate of one node is originally less than the x coordinate of another, this relation will still hold in the transformed layout. The similar properties hold for the y coordinates. This is not quite true for the "porth*" cases. For these, orthogonal ordering is only preserved among nodes related by an edge.

Valid on:
  • Graphs
Note: not dot