densify - Automatically adding vertices to lines every x meters using QGIS?

I've made a vector grid using lines; the grid coverage is 100 km x 100 km and the lines are at vertical and horizontal intervals of 1000 metres. Each line in the grid is defined by two vertices, one at each end, and each line has an ordinate attribute for labelling.

My wish is to to add vertices to the lines, so that each line will have vertices at intervals of (say) 500 metres. Does anyone know how to do this?

The background to this is that the grid will be displayed on OpenLayers and given the strangeness of Google Mercator the lines need to be pegged to the ground with vertices at frequent intervals. One other obvious use for the ability to add vertices to grid lines would also be to make nicely curved lat/lon graticules for projected maps.

Answer

in Qgis 1.8.0 there is a densify function but i don't know if it has distance parameter like in Arcgis