protected void initCrossHairs() {
        //guiFont = assetManager.loadFont("Interface/Fonts/Default.fnt");
        BitmapText ch = new BitmapText(guiFont);
        ch.setSize(guiFont.getCharSet().getRenderedSize() * 2);
        ch.setText("+"); // crosshairs
        ch.setLocalTranslation( // center
                settings.getWidth() / 2 - guiFont.getCharSet().getRenderedSize() / 3 * 2,
                settings.getHeight() / 2 + ch.getLineHeight() / 2, 0);
        guiNode.attachChild(ch);
    }
Creates a terrain object and a collision node to go with it. Then
drops several balls from the sky that collide with the terrain
and roll around.
Left click to place a sphere on the ground where the crosshairs intersect the terrain.
Hit keys 1 or 2 to raise/lower the terrain at that spot.

@author Brent Owens
jme3-examples/src/main/java/jme3test/terrain/TerrainTestCollision.java