Calculate rotation to set on static mesh component to face location in world space?

Legacy UDK Programming and UnrealScript
1

I’m trying to have a static mesh component of an actor face towards a location in world space.

The function I have so far works fine if the actor is on a flat horizontal surface, but when on a slope (so it’s Pitch and Yaw are != 0), the rotator doesn’t point accurately. Code:

simulated function PointMeshCompAtWorldLoc(vector worldLoc) 
{
    local rotator faceToLoc;

    faceToLoc = Rotator(worldLoc - Location) - Rotation;

    MyMeshComp.SetRotation(faceToLoc);
}

Anyone know what I’m missing here? Thanks in advance.

2

Would it be good enough if instead of using the whole rotation, you just used the yaw?

simulated function PointMeshCompAtWorldLoc(vector worldLoc) 
{
    local rotator faceToLoc;
    local rotator YawOnly;

    YawOnly.yaw = Rotation.yaw;

    faceToLoc = Rotator(worldLoc - Location) - YawOnly;

    MyMeshComp.SetRotation(faceToLoc);
}

My only other suggestion would be to use quaternions wherever possible.

3

I’ve read several other places that mention using quaternions for similar tasks.

I’m honestly not really sure where to start. Guess i need to turn to ChatGTP to get some pointers…

If you have any tips/examples, they would be welcome.
Cheers

4

Open up Object.uc and do a search for “Quaternion functions” and you’ll see a comment with a bunch of functions under it. That’s your toolbox. I think you’ll want to do this:

simulated function PointMeshCompAtWorldLoc(vector worldLoc) 
{
    local rotator faceToLoc;
    local Quat QuatToTarget;

    QuatToTarget = QuatFindBetween(Location, worldLoc);
    faceToLoc = QuatToRotator(QuatToTarget);
    faceToLoc -= Rotation;
    MyMeshComp.SetRotation(faceToLoc);
}
5

Thanks for the suggestion. I wasn’t able to get it to work correctly though. I ended up deciding to keep the actor only rotating it’s yaw, so that i could continue using my original function. And then just rotate other smc’s it has to simulate the actor rotating.

I’d like to revisit it at a later date to implement the proper solution, but for now I’ll have to leave the hack solution in place, which works fine. Frustrating to not solve it though…

6

This simple function works for me.

function FindAimToHit(Vector Origin, out Vector AimSpot, out Rotator AimRotation)
{
AimRotation = Rotator(AimSpot - Origin);
}