finding the midPoint, VectorManipulation

#1 For vectors A and B, to get the vector C from A to B, you take the difference: C = B - A

Since you want a vector D, representing half the distance, divide the elements of C by 2:
D.x = C.x / 2.0
D.y = C.y / 2.0

Add your resulting vector to the first (A) to get the vector E that represents the midpoint between A and B:
E = D + A

#2 Thanks Richard,
But I came across one problem.

If the distance is not absolute, it can sometimes pick the wrong vector. For instance if...

Vector1 (10, 9)
Vector2 (3, 7)

t2dVectorSub is (Vector2 - Vector1),
in which case the result is (-7, -2)
This relut is not ideal.



How would you deal with negative and positive results from the t2dSubtraction and insuring the vector ultimately used for the midPoint is neither the opposite X or Y value required?

#3 The vector (-7, -2) represents the DIRECTION of the vector that goes between the two (and the length of that vector is the distance between the two, by the way). Half that vector, (-3.5, -1), represents half the distance in the same direction of course. Adding the vector (-3.5, -1) to the first vector (10, 9) will yield the vector (6.5, 8), which is indeed the midpoint between (10, 9) and (3, 7).

#4 hmm. ok. I am going to go over this. If I have any more questions I will ask for sure.


Thanks!

#5 Draw the lines on a graph to help you visualize it. Draw a line from A to B, and then draw the vector C that results from subtracting B - A. Notice that C is the exact same length and direction as the line from A to B. Also, remember when drawing a vector on a graph, you should put an arrow on the end of the line, as a vector describes a direction. That way, you can see that A-B and B-A yield different vectors of the same size, pointing in opposite directions.

#6 If (vectorAx, vectorAy) and (vectorBx, vectorBy) are Points and not Vectors, the midPoint between A and B is easily calculated by :

M = ( A + B ) / 2.0;

So

vectorMx = (vectorAx + vextorBx)/2.0;
vectorMy = (vectorAy + vextorBy)/2.0;

Nicolas Buquet
www.buquet-net.com/cv/

#7 Oh great. Thanks. It has been so long since high school Algebra.

#8 Oh yeah, that works, too. I guess I overcomplicated it :)