//gradient_play.bvr\nv=vectorField\nv.setInterval=x,1.0\nv.setInterval=y,1.0\nv.setInterval=z,1.0\nv.setMinMax=x,-2,2\nv.setMinMax=y,-2,2\nv.setMinMax=z,4,4\nv.setEquation=x,(1000*x)\nv.setEquation=y,(1000*y)\nv.setEquation=z,(0)\nv.color=green\nv.spawn\n\nsu=parametricSurface\nsu.setMinMax=s,-2,2\nsu.setMinMax=t,-2,2\nsu.setEquation=x,(s)\nsu.setEquation=y,(t)\nsu.setEquation=z,(s*s+t*t-4)\nsu.setSegmentCount=20\nsu.color=red\nsu.spawn