Get modelViewProjectionMatrix and viewportTransformation

I would like to use

https://cesium.com/downloads/cesiumjs/releases/1.40/Build/Documentation/Transforms.html#.pointToWindowCoordinates
Cesium.Transforms.pointToWindowCoordinates(modelViewProjectionMatrix, viewportTransformation, point, result)

from where/how do I get the modelViewProjectionMatrix and viewportTransformation ?

@Maginboo

Thank you for your question! Is there any reason why you are looking at the documentation from CesiumJS 1.40 instead of the most recent version of CesiumJS?

-Sam

Well, I have an old version, I checked the new one. But my knowledge might not help in knowing how to use this.
https://cesium.com/downloads/cesiumjs/releases/1.61/Build/Documentation/Transforms.html?classFilter=Trans

modelViewProjectionMatrix

viewportTransformation

In my mind, something called pointToWindowCoordinates should give me the window coordinate of a point, are this modelViewProjectionMatrix, viewportTransformation easily obtainable from the camera ?