How can I add points and vectors to the following plot in order to illustrate gradient descent?
#import "@preview/plotsy-3d:0.2.0": plot-3d-surface, plot-3d-parametric-curve
#let f(x1, x2) = calc.pow(x1, 2) - 2 * x1 * x2 + 2 * calc.pow(x2, 2) + 2*x1
#align(center)[
#let size = 5
#let scale-factor = 0.15
#let (xscale,yscale,zscale) = (0.7,0.3,0.01)
#let scale-dim = (xscale*scale-factor,yscale*scale-factor, zscale*scale-factor)
#let func(x,y) = x*x + y*y
#let color-func(x, y, z, x-lo,x-hi,y-lo,y-hi,z-lo,z-hi) = {
return blue.transparentize(20%).darken((y/(y-hi - y-lo))*100%).lighten((x/(x-hi - x-lo)) * 50%)
}
#plot-3d-surface(
f,
color-func: color-func,
subdivisions: 1,
subdivision-mode: "decrease",
scale-dim: scale-dim,
xdomain: (-size,size),
ydomain: (-size,size),
pad-high: (0,0,0),
pad-low: (0,0,0),
axis-step: (2,2,50),
dot-thickness: 0.05em,
front-axis-thickness: 0.05em,
front-axis-dot-scale: (0.05,0.05),
rear-axis-dot-scale: (0.08,0.08),
rear-axis-text-size: 0.5em,
axis-label-size: 1em,
xyz-colors: (black,black,black),
axis-labels: ($x_1$, $x_2$, $y$),
)
]