Plot function

const Plot = ({fx, length, resolution}) => {

    const vertices = [];
    const indices = [];
    const radialSegments = 50;
    const rings = resolution;

    const addVertex = (v) => {
      vertices.push(v.x,v.y,v.z);
    }

    const addIndex = (x) => {
      indices.push(x);
    }

    const P = (x,y,dy,r,u) => {
      const normal = -1/dy;
      return {
        x: x + r*Math.cos(u) * 1,
        y: y + r*Math.cos(u) * normal,
        z: r*Math.sin(u)
      }
    }
    const U = (x) => {
      return x/radialSegments * Math.PI * 2;
    }
    const X = (x) => {
      return (x/rings-length/2);
    }

    const r1 = 0.1;

    for(let i = 0; i < length*rings; i++) {
      const x = X(i);
      const x1 = X(i-1);

      const y = fx({x:x});
      const y1 = fx({x:x1});

      const h = 1e-2;
      const dy = (fx({x: x+h}) - fx({x :x-h})) / (2*h)
      const dy1 = (fx({x: x1+h}) - fx({x :x1-h})) / (2*h)

      if(Math.abs(y) >= length/2)
        continue;

      for(let j = 0; j <= radialSegments; j++) {

        const v0 = P( x,  y,  dy, r1, U(j)  );
        const v1 = P( x,  y,  dy, r1, U(j+1));
        const v2 = P(x1, y1, dy1, r1, U(j+1));
        const v3 = P(x1, y1, dy1, r1, U(j)  );

        addVertex(v0);
        addVertex(v1);
        addVertex(v2);
        addVertex(v3);


        const index = vertices.length / 3;

        addIndex(index);
        addIndex(index + 1);
        addIndex(index + 2);

        addIndex(index);
        addIndex(index + 2);
        addIndex(index + 3);
      }
    }

    const positionAttribute = new BufferAttribute(new Float32Array(vertices), 3);
    const indexAttribute = new BufferAttribute(new Uint32Array(indices), 1);
    const customGeometry = new BufferGeometry();
    customGeometry.setAttribute('position', positionAttribute);
    customGeometry.setIndex(indexAttribute);
    customGeometry.computeVertexNormals();
    return (
      <>
      <mesh geometry={customGeometry}>
        <meshStandardMaterial color={0xff0000} side={DoubleSide} flatShading={true}/>
      </mesh>
      </>

    )
}