Casting shadows on transparent plane

#1

Hi,

I need to cast shadows on a transparent plane in order to get only the shadow shown and not the material applied to the plane (I want it fully transparent).

For example, is there a solution to cast a shadow while hiding the mesh itself?

This is a sample of three.js.
https://threejs.org/examples/webgl_geometry_spline_editor.html

I want to reproduce this with openframeworks! !