# Changing magnitude of vector changes its direction

Hi,

I built a weaponsystem for my game which checks for hits via line trace (just like in the shooter example). It works like a charm but I decided to add a bouncing effect yesterday. I want the trace to bounce off a wall and check there also for hits. I already achieved this, however I got a much more simple problem now: I can’t scale the magnitude of the ricocheted line whatsoever. I don’t want the bouncing ray to be the same size as the incoming ray but a bit smaller.

I thougth it was simple Math and I just needed to multiply the “BouncingVector” by 0.1 or something, but if I do this, it ends up chaning its direction as seen on the second screenshot. I always thougth multiplying a vector doesn’t affect its direction but just its magnitude?

non-changed BouncingVector (correct direction):

http://puu.sh/k9BV8/c2f3674f12.jpg

BouncingVector = BouncingVector*0.1 (changes direction):

http://puu.sh/k9BXo/84e7c040ea.jpg

Here is my code so far:

function where the problem lays:

http://puu.sh/k9C6S/d5ab02753c.png

calling the function:

http://puu.sh/k9C8u/e9c4b4e1a0.png

Can someone perhaps put me out of my misery?

Cheers
~Theo

P.S: I got a workout going, thanks to Ctzn07:

``````FRotator LookAtRot = UKismetMathLibrary::FindLookAtRotation(Hit.Location, BouncingVector);
FVector test = UKismetMathLibrary::GetForwardVector(LookAtRot) * 200 + Hit.Location;
``````

But would still like to know why it’s changing the direction when multiplied like above. :o

I think this line is wrong:

``````FVector BouncingVector = EndTrace.MirrorByVector(Hit.ImpactNormal);
``````

You are mirroring the EndTrace vector which is just the end location of your weaponrange which is a vector from (0,0,0) to the EndTrace.

Instead you should mirror the remaining vector from the impact point to endtrace (which should be parallel with ShootDir):

``FVector BouncingVector = (EndTrace - Hit.ImpactPoint).MirrorByVector(Hit.ImpactNormal);``