Re: Scripting : Align along normal

[guillaume laforge <guillaume.laforge.3d(at)gmail.com>]

Thanks for the help Kim. Raf function gives me a clearer vision of matrix use with XSI :-). So two vector cross products are needed to create the 3X3 matrix ? Not so complicated :-)

 

However, I found my problem. It came from a wrong normal vector. Maybe some users on this list learn 3d math like me so here is the answer : 

 

 In my previous script the polygon normal is :

//---------------------------------------------------------
var polySel = Selection.item(0).subcomponent.componentcollection;
var oPolygonFace = polySel(0);
//Get the Polygon Normal
var oPolygonNode = oPolygonFace.Nodes(0);
var >//-------------------------------------------------------
 

In fact it returns a point normal.

So I use this snipet to find the polygon normal :

//---------------------------------------------------------
//Get the selected polygon
var polySel = Selection.item(0).subcomponent.componentcollection;
var oPolygonFace = polySel(0);
nbPoints = oPolygonFace.NeighborVertices (1);
var >for(i=0;i<nbPoints.count;i++)
{
   oNormal.AddInPlace(nbPoints.item(i).normal);
}
oNormal.ScaleInPlace(1/nbPoints.count);
//---------------------------------------------------------

Thanks to Heldge Mathee for his scripting tutorials (Getting Started with Scripting in SOFTIMAGE|XSI ). It helps a lot !

Cheers,

Guillaume Laforge
Cg Artist | Jr Td

 

2005/10/31, kim aldis <kim(at)cg-soup.com>:

try this, with thanks to Raf. vDir is the normal vector, vUp is the, um, up vector. the normalisation of the vectors is quite important:

 

function OrientateToVector( vDir, vUp ) {

 

 var vp1 = XSIMath.CreateVector3();
 var vp2 = XSIMath.CreateVector3();

 

 var vMat3 = XSIMath.CreateMatrix3()

 

 vUp.NormalizeInPlace();
 vDir.NormalizeInPlace();

 

 vp1.Cross( vDir , vUp );
 vp2 .Cross( vp1, vDir );
 vp1.NormalizeInPlace();
 vp2 .NormalizeInPlace();
  
 vMat3.Set(
    vp1.x, vp1.y, vp1.z,
    vDir .x, vDir .y, vDir.z ,
    vp2.x, vp2.y, vp2.z
   );

 

 oRotation= XSIMath.CreateRotation();
 oRotation.SetFromMatrix3( vMat3 );
 oRotation.GetXYZAngles( vp1 );

 

 return vp1

 

}

---

From: owner-xsi(at)Softimage.COM [mailto: owner-xsi(at)Softimage.COM] On Behalf Of guillaume laforge
Sent: 31-October-2005 12:34
To: XSI(at)Softimage.COM
Subject: Scripting : Align along normal

 

Hi list :-)

 

I'm learning XSIMath and I can't find how to align an object along the POLYGON normal ? My script seems to work but it doesn't align perfectly along polygon normal :-/. As I'm new to those things I'm wondering if I miss something in the 3d math logic or if in XSI the polygon normal is a special case (compared to normals on points ).

 

Here is my script :

 

//AlignAlongNormal.js
//Select one polygon, run the script and pick an object.
//-----------------------------------------------------

//Get the selected polygon
var polySel = Selection.item(0).subcomponent.componentcollection;
var oPolygonFace = polySel(0);
//Get the Polygon Normal
var oPolygonNode = oPolygonFace.Nodes(0);
var >
//Get the Polygon points
1 );
//-----------------------------------------
//Find the Position.
var oPos = XSIMath.CreateVector3();
for ( var i = 0 ; i < oNborsPoints.count ; i++ )
{
oPos.x = oPos.x+oNborsPoints(i).Position.x;
oPos.y = oPos.y+oNborsPoints(i).Position.y;
oPos.z = oPos.z +oNborsPoints(i).Position.z;
}
oPos.x = oPos.x/oNborsPoints.count;
oPos.y = oPos.y/oNborsPoints.count;
oPos.z = oPos.z /oNborsPoints.count; 

//-------------Align the picked object------------------
//Pick session
var oPicked = PickObject ("Please pick an object") ;
var buttonChoice = oPicked.Value( "ButtonPressed" ) ;
var MyObj = oPicked.item(2);

//Rotation
MyObj.kinematics.global.transform = RotationFromPoly(oNormal) ;

//Position
MyObj.Kinematics.Global.Parameters("posx").value = oPos.x;
MyObj.Kinematics.Global.Parameters("posy").value = oPos.y;
MyObj.Kinematics.Global.Parameters("posz").value = oPos.z;

//**********From Ray-T Function**********
function RotationFromPoly(polyNormal)
{
var upVec = XSIMath.CreateVector3();
upVec.set(0, 1, 0);
var axis = XSIMath.CreateVector3();
axis.cross(upVec, polyNormal);
var angle = Math.acos(upVec.dot(polyNormal));
var rot = XSIMath.CreateRotation();
rot.SetFromAxisAngle(axis, angle);
var transfo = XSIMath.CreateTransform();
transfo.SetRotation(rot);

return transfo;
}

Any advice from experienced user is welcome !

Cheers,

Guillaume Laforge
CG artist | Jr td :)