Can anyone gives a little hint about cutsom rotator node calculation proof maybe?

[ClockworkOcean]

@WoodenAX

hi guys I am kind new to material system, just start to learn a bit about the textCoord calculation. In the engine default node “Custom rotator”, in the node it gives this:

so…what I understand is, texcoord put every UV point like(0,0), (0,0.1)… those point into the calculation to change the texture sample, but how they use dot product from UV point and a (sine, cosine) vector to obtain the rotating result of each X axis point? I tried to find the relationship between trignometry and dot product but still no clue, maybe I miss something. So can anyone explain that for me please?

I can’t give you a proof, not without developing a notation system first, which I’m not going to do, but…

I can help you to realize roughly what’s going on. You need to view the graph in 3 parts really:

Part1

Part 2

Part 3

Part 1 is essentially taking the pivot point and measuring the distance between each pixel ( UV coord ) and that pivot point. This in itself is a vector or direction.

Part 2 is taking the angle of rotation and producing a constant X. It’s basic trig, you’ve given an angle, and we know the distance from the rotation origin. A crucial point is that the stuff in part 1 is different for every pixel. Two constants are developed here, because we are dealing with U and V.

Part 3 Dot product tells you how ‘different’ directions are. 1 for the same, 0 for right angles, -1 for opposing. So this part3 is looking at how far away the rotation of the pixel is from the required angle and correcting it. The append is putting the X,Y ( U,V ) back together and then adding the pivot point offset.

I hope that makes some sort of sense.