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.

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 ?