How to mask on a shader , limit a shader to an area in a ScrollView?

Hello!

I am adding a heatmap shader onto my map in a scrollview with a mask.

The scrollview with a mask enables you to drag the big map and show its other part in the small limited rounded rectangle area.

Now the heatmap is also part of the content of the scrollview and can be dragged together with the map underneath.

My problem is the heatmap is not masked and go out of the area.

As you see the map is limited to a rounded rectangle area, but the heatmap shader on the map just shows its whole.

It seems that the mask component in the scrollview does not work with the heatmap shader.

What can I do to also mask the heatmap shader and limit it to the scrollview area as well?

I am totally new with material , shader and texture.

Thank you very much!

heatmap

scrollview with a mask component