Spawn an object facing a point

[Port]

I'm trying to create an object which is rotated towards a specific point. I have a 3D vector of the positional difference, but TGE uses axis angles for rotation. I've tried the following three methods of conversion, but none of them work properly. Any ideas?

Code: [Select]

function vectorToAxis( %vector )
{
%normal = vectorNormalize( %vector );

%axis = vectorCross( %vector, %normal );
%angle = vectorDot( %vector, %normal );

return %axis SPC %angle;
}


Code: [Select]

function vectorToAxis( %vector )
{
%axis = vectorCross( %vector, "0 0 1" );
%angle = vectorDot( %vector, "0 0 1" );

return %axis SPC %angle;
}


Code: [Select]

function vectorToAxis( %vector )
{
%angle = mAtan( getWord( %vector, 1 ), getWord( %vector, 0 ) );
return "0 0" SPC %angle SPC 1;
}


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[Port]

Er, nevermind, I've managed to get it working by stitching together some resources from various places.

Code: [Select]

function vectorToAxis( %vector )
{
%pi = 3.1415926535897932384626433;

%x = mASin( getWord( %vector, 0 ) ) * 180 / %pi;
%y = mACos( getWord( %vector, 1 ) ) * 180 / %pi;

%angle = 180 - mFloatLength( %x / mAbs( %x ), 0 ) * ( 180 - %y );
%euler = vectorScale( "0 0" SPC %angle, $pi / 180 );
%matrix = matrixCreateFromEuler( %euler );

return getWords( %matrix, 3, 6 );
}

It only handles Z rotation, but that's fine for my use case.

[Xalos]

Is that level of detail on Pi even meaningful? I usually stop at the second 5, and even that is dropped by Torque.

[Rotondo]

Try this.

Code: [Select]

function vectorToAxis( %vec )
{
%x = getWord( %vec, 0 );
%y = getWord( %vec, 1 );

%yawAng = mAtan( %x, %y );

if( %yawAng < 0.0 )
{
%yawAng += $pi*2;
}

%rot = "0 0 1" SPC %yawAng;

return %rot;
}
You should always double check your code against some known value. For instance we know that vector 0 1 0 is equal to the rotation of 1 0 0 0 or north. We can test this by setting our transform to be "0 0 0 1 0 0 0" then returning our forward vector.

[Xalos]

I believe he wants to have the object spawn rotated in three dimensions to face a given point, not just rotated in two.
I could be mistaken about that, though.

[.Trinick]

What's with the sudden fascination with rotating objects to face others? I'll get Truce to post his solution here or ask Dotdotcircle for whatever he came up with.

[Brian Smithers]

You should put in more default Vector functions Rot.
Also something to make players look at a certain point ;)

[Port]

I believe he wants to have the object spawn rotated in three dimensions to face a given point, not just rotated in two.
I could be mistaken about that, though.

Rotondo's solution works perfectly for my usage scenario.