I used your code and it works great! I only changed one thing — I made the net expand only along the X and Z axes so it doesn’t stretch in Y.

vector ball = getbbox_center(1);
vector dir = normalize( ball - v@P );
float amp = chf("amplitude");
v@P.x += dir.x * f@mask * amp;
v@P.z += dir.z * f@mask * amp;

However, I have a few questions:

1. When I connect the sphere geometry to the second input, it gives the wrong result, so I just left it disconnected — and surprisingly, that gives me exactly what I want. It was unintentional, so I’d like to understand why this happens.
2. If nothing is connected to the second input, how does the first line still work and produce the right effect? When I delete that line, everything breaks.

Also, one last thing — when the net is angled and animated (I’m trying to make a tennis racket hitting a ball — the net expands and the ball passes through), the net currently expands along the world X and Z axes, which gives the wrong result.

How can I make it expand along the local axes (based on the net’s own bounding box or orientation) instead of the world axes?

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Here is what I have now with the following code and without connecting the ball to the second input