Hi Kris,
I've tried this and I think this should work.
Add an "Every N Frame" event to the particles, and set the event "value" to
zero so that the event triggers at every update. Set the event Action to
"Script" and on the Script tab, set the ScriptContext to "Per Particle".
You can then use something like this as your script:
//-----------------------------------------------------
var ppos = XSIMath.CreateVector3()
ppos.Copy(inParticle.Position);
var col = new ActiveXObject("XSI.Collection");
col.Items="Camera";
cam = col(0);
var campos = XSIMath.CreateVector3();
cam.kinematics.global.transform.GetTranslation(campos);
var xdir = XSIMath.CreateVector3();
var ydir = XSIMath.CreateVector3();
var zdir = XSIMath.CreateVector3();
ydir.Set(0,1,0);
zdir.sub(campos,ppos);
zdir.NormalizeInPlace();
xdir.cross(ydir,zdir);
xdir.NormalizeInPlace();
ydir.cross(zdir,xdir);
ydir.NormalizeInPlace();
var mat = XSIMath.CreateMatrix3();
mat.Set(xdir.x, xdir.y, xdir.z, ydir.x, ydir.y, ydir.z, zdir.x, zdir.y,
zdir.z);
var rot = XSIMath.CreateRotation();
rot.SetFromMatrix3(mat);
var angles = XSIMath.CreateVector3();
rot.GetXYZAngles(angles);
inParticle.Rotation = angles;
//-----------------------------------------------------
Obviously, you'll need to change the string "Camera" to whatever you need
the particles to look at. This script points the z axis of the particle at
the camera, so you might need to alter this to work with what you've got.
The other thing to note, is that you might get better performance if you use
an external script file, since you'll be able to move the
"XSIMath.CreateXXXXXX" and "new ActiveXObject" calls outside the update
function so they only get called once (just make sure you initialise the
objects properly).
Cheers
Andy
-----Original Message-----
From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf Of
Kris Rivel
Sent: 10 April 2006 23:16
To: XSI List Server
Subject: particle instance direction constraint
I'm looking to have all my particle instances point towards the camera.
Can this be done? I have too many and can't plot them out as objects....I
need them to remain as particle instances. Any ideas?
Kris
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