I am trying to find more explanation of this method but still can not understand it.

It is hard to make sense to me by only semantic explanation.

As far as I found, it is to compute the areas of the orthographic projection of the polygon, but could anyone illustrate this idea?

Thank you so much~

Where did you got this from ? This sounds not very detailed.

The GL wiki seem better :

http://www.opengl.org/wiki/Calculating_a_Surface_Normal

And this post on gamedev explains that it is the ortho projection for each axis that are taken in account :

http://www.gamedev.net/topic/416131-calculating-a-polygon-normal/page__p__3771628#entry3771628

Thank you for sharing your information with me.

There is the source I found from Ray-Polygon and Ray-Quadric Intersection Testing

I understand how to calculate Area of irregular polygons in 2D but for Newell’s method, I can not comprehends its principle.

If (A, B, C) are the plane’s normal and Why can we get A by calculating 2 x area of projection onto yz plane?

I just think one illustration can make me understand better.

Thank you again.