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Spawn based on player location and using player rotation

So, this is causing me few headaches, so I thought I'd ask on here... I'm trying to work out how to spawn an actor at a random location within a defined 'area' that is based on the player location (which I can do), but that also takes into account the player rotation (which I can't do!). The idea being that then I could always spawn something behind, in front of or off to one side of the player.

I can do this without taking into account the player' location - just the location, break the vector, apply some offsets and then remake the vector. This gives this:

alt text

The problem is I can't work out how to get this:

alt text

Can anyone offer any suggestions?


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asked Dec 14 '14 at 06:03 PM in Using UE4

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1 answer: sort voted first

First of all look at this picture to know what I mean about GetActorForwardVector and GetActorRightVector.

alt text

As an example, I am going to write the pseudo code for generating a random location behind the player (the orange area).

 Vector3 GetRandomLocBehindActor(AActor* P , float AreaW , float AreaH)
    Vector3 localX = P->GetActorRightVector()*RandBetween(-AreaW/2 , AreaW/2);
    Vector3 localY = P->GetActorForwardVector()*RandBetween(-AreaH , 0);
    return localX+localY+P->Location;

Look at these links too GetActorRightVector() , GetActorForwardVector() , GetActorUpVector()

feel free to comment if you find this answer too short and need more explanation.

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answered Dec 14 '14 at 08:32 PM

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avatar image teed Dec 15 '14 at 04:18 PM

Hi Sachamora, Thanks for the advice - I think that all makes sense! Don't know why I didn't think of doing it like that..! I'll give it a go and let you know how I get on...


avatar image teed Dec 15 '14 at 08:19 PM

Hey! So, it turns out, I didn't understand your reply as well as I thought once I tried to implement it! If I just use the vector based on the GetForwardVector things spawn in a nice line directly behind the player and taking into account for the player rotation. If I use the GetRightVector they do the same, but obviously in a line to the left/right of the player. However, the problem comes when I try and combine these 2 vectors... If I do vectorF + vectorR (or localX + localY in your pseudo code) then it doesn't work - have I got something wrong?

I'm doing this in a BP - so here's a screenshot of my setup

alt text

Any further advice would be greatly appreciated! Thanks

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avatar image Sachamora Dec 15 '14 at 09:35 PM

Hi, My mistake, I will update the pseudo code in answer, here is what you must change in your BP:

alt text

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avatar image teed Dec 15 '14 at 11:59 PM

That's got it! Thanks for the help - much appreciated.

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