A query about trimesh selections


#1

because in max trimesh face vert order is CCW Does this mean that say on selections if you collect edges of the selection in face vert order then “exterior” edges always go CCW and “interior” edges always go CW ?


#2

i don’t think so…
is not always going reverse to the pair edge.

Lets say we have triangles [1,2,3] and [4,2,3] . Edge 2 (2,3) of triangle 1 and edge 2 (2,3) of triangle 2 are ‘reversed’ but both are going same direction. But we can change the triangle 2 to different order - [4,3,2] for example. In this case second edges of triangles are going reversed to each other.


#3

That would also flip the face normal.

(
	obj = converttomesh (plane length:100 width:100 lengthsegs:1 widthsegs:1)
	
	f1 = getface obj 1
	f2 = getface obj 2
	format "  face1:%   face2:%\n" f1 f2
	
	n1 = getfacenormal obj 1
	n2 = getfacenormal obj 2
	format "normal1:% normal2:%\n\n" n1 n2
	
	setface obj 2 [f2[1],f2[3],f2[2]]
	update obj
	
	f1 = getface obj 1
	f2 = getface obj 2
	format "  face1:%   face2:%\n" f1 f2
	
	n1 = getfacenormal obj 1
	n2 = getfacenormal obj 2
	format "normal1:% normal2:%\n" n1 n2
)

@Klvnk
At first glance I would think yes, the outer and inner edges goes in the direction you have described, but I can’t make a statement out of it.


#4

turns out I’d didn’t need it, though it’s an interesting property if it is the case.


#5

you are right… but i was talking about “average” normal of selection (or set of triangles). like was shown on the picture.