Maxscript: This example demonstrates how to calculate the offset for a corner point. It allows users to define how far to offset the new point from it's original location.

Offset Corner Point | .ms

/* Test Scene Setup */
clearlistener()
delete objects

/* generate an array of random points */
randomPts = for i = 1 to 3 collect (random [-30,-30,0] [30,30,0])

/* Requires 3 point3 values */
fn CalculateOffset offset:8 ptA:undefined ptB:undefined ptC:undefined =
(
	BA = ptB-ptA
	BC = ptB-ptC
	ang = acos(dot (normalize BA) (normalize  BC) )
	vec = normalize(normalize(BA) + normalize(BC))
	P1 = vec * offset + ptB
)
	
fn GenerateOffset pts:#() =
(
	a = CalculateOffset ptA:pts[1] ptB:pts[2] ptC:pts[3]
	b = CalculateOffset ptA:pts[3] ptB:pts[1] ptC:pts[2]
	c = CalculateOffset ptA:pts[2] ptB:pts[3] ptC:pts[1]
	
	/* spline showing original positions */
	sp = splineShape wirecolor:yellow
	addNewSpline sp
	addKnot sp 1 #corner #line pts[1]
	addKnot sp 1 #corner #line pts[2]
	addKnot sp 1 #corner #line pts[3]
	close sp 1
	updateShape sp
	
	/* offset points */
	point pos:a wirecolor:green size:2
	point pos:b wirecolor:green size:2
	point pos:c wirecolor:green size:2
)

GenerateOffset pts:randomPts