Math problem in the content example

[anonymous_user_6dda2803]

I am study on the Math Hull example, there is a 2.20, use camera vector to make the object with the material face the actor.
In the material:

I just don’t get it. The X+Y already have the plane right? so what the rest mean? Why subtract absolute world position and add actor position?
Please help me, guys. Thx a lot.

[anonymous_user_6dda2803]

ok, I solved this my self. it can look at use abs position - actor position, this is the vector for origin plane’s pix vector, and the x+y is the new vector ,so the world offset is equal to use the new vector - the old vector. haha.
Can believe it took my 5 hours to understand it.