protected void createShape() {

        HeightfieldTerrainShape shape = new HeightfieldTerrainShape(heightStickWidth, heightStickLength, heightfieldData, heightScale, minHeight, maxHeight, upAxis, flipQuadEdges);
        shape.setLocalScaling(new javax.vecmath.Vector3f(scale.x, scale.y, scale.z));
        cShape = shape;
        cShape.setLocalScaling(Converter.convert(getScale()));
                cShape.setMargin(margin);
    }
Uses Bullet Physics Heightfield terrain collision system. This is MUCH faster
than using a regular mesh.
There are a couple tricks though:
   -No rotation or translation is supported.
   -The collision bbox must be centered around 0,0,0 with the height above and below the y-axis being
   equal on either side. If not, the whole collision box is shifted vertically and things don't collide
   as they should.

@author Brent Owens
jme3-jbullet/src/main/java/com/jme3/bullet/collision/shapes/HeightfieldCollisionShape.java