How to cut model using clipping plane properly?

Questions
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1

I have a model of building and I want to cut it using a clipping plane to a specific part. It is clipping but there are some shadows of the real model stays with it.

Screenshot (13)
Screenshot (13)879×836 218 KB

You can see it in the image. I have clipped it from the top to the marked point. It is clipped but still, there is some kind of blurry shadows of the clipped part you can see. It is not removed. How can I remove this?

I have used this code:

const [cutPlane, setCutPlane] = useState(-150);
const localPlane = new THREE.Plane(new THREE.Vector3(0, cutPlane, 0), 0.8);

I’m setting the cutPlane value to cut to a certain point like this:

setCutPlane(-50)

I’m using react three fiber. Help me if you know how to do this. Thanks