OpenLayers: Z-Ordering and Y-Ordering of Vector Features

# Z-Index/Y-Order Example

stack, stacking, zindex, ordering, light

This example shows the use of z-indexing and y-ordering of external graphics. Zoom in and out to see this behavior.

### Z-Index (with Y-Ordering enabled)

In this map, the gold features all have the same z-index, and the red features have alternating z-indeces. The gold features' z-index is greater than the red features' z-indeces, which is why gold features look to be drawn on top of the red features. Since each gold feature has the same z-index, gold features succomb to y-ordering: this is where features that seem closest to the viewer (lower lattitude) show up above those that seem farther away (higher lattitude).
You can enable y-ordering by passing the parameter yOrdering: true in the vector layer's options hash. For all configurations (with yOrdering or zIndexing set to true), if features have the same z-index -- and if y-ordering is enabled: the same latitude -- those features will succomb to drawing order, where the last feature to be drawn will appear above the rest.

### Z-Index and Drawing Order (Z-Indexes set, and Y-Ordering disabled)

In this map, zIndexing is set to true. All features are given the same z-index (0), except for the first feature which has a z-index of 1. The layer's yOrdering parameter is set to the default (false). This configuration makes features succomb to z-index and drawing order (for the features with the same z-index), instead of y-order.
The features in this map were drawn from left to right and bottom to top, diagonally, to show that y-ordering is not enabled. Only the lower-left corner feature is drawn on top of the others, because it has a higher z-index (1 instead of 0).