@Override
    public float getHeight(Vector2f xz) {
        // offset
        float x = ((xz.x - getWorldTranslation().x) / getWorldScale().x) + (totalSize-1) / 2f;
        float z = ((xz.y - getWorldTranslation().z) / getWorldScale().z) + (totalSize-1) / 2f;
        if (!isInside((int)x, (int)z))
            return Float.NaN;
        float height = getHeight((int)x, (int)z, (x%1f), (z%1f));
        height *= getWorldScale().y;
        return height;
    }
Get the interpolated height of the terrain at the specified point.
@param xz the location to get the height for
@return Float.NAN if the value does not exist, or the coordinates lie outside the terrain
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/TerrainQuad.java